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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2013-10-08 20:23:47 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2013-10-15 12:53:31 -0700
commit4102adab9189c8ea2f0cdd2f88345fd25d2790f1 (patch)
tree235964cfd9c09a5c642a2d0d8745a651a0d4bcfa /kernel/rcutree.c
parent252997330908cb8ee3d5714539ed967b977c2eae (diff)
downloadlinux-4102adab9189c8ea2f0cdd2f88345fd25d2790f1.tar.bz2
rcu: Move RCU-related source code to kernel/rcu directory
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/rcutree.c')
-rw-r--r--kernel/rcutree.c3396
1 files changed, 0 insertions, 3396 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
deleted file mode 100644
index 240604aa3f70..000000000000
--- a/kernel/rcutree.c
+++ /dev/null
@@ -1,3396 +0,0 @@
-/*
- * Read-Copy Update mechanism for mutual exclusion
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
- *
- * Copyright IBM Corporation, 2008
- *
- * Authors: Dipankar Sarma <dipankar@in.ibm.com>
- * Manfred Spraul <manfred@colorfullife.com>
- * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version
- *
- * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
- * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
- *
- * For detailed explanation of Read-Copy Update mechanism see -
- * Documentation/RCU
- */
-#include <linux/types.h>
-#include <linux/kernel.h>
-#include <linux/init.h>
-#include <linux/spinlock.h>
-#include <linux/smp.h>
-#include <linux/rcupdate.h>
-#include <linux/interrupt.h>
-#include <linux/sched.h>
-#include <linux/nmi.h>
-#include <linux/atomic.h>
-#include <linux/bitops.h>
-#include <linux/export.h>
-#include <linux/completion.h>
-#include <linux/moduleparam.h>
-#include <linux/percpu.h>
-#include <linux/notifier.h>
-#include <linux/cpu.h>
-#include <linux/mutex.h>
-#include <linux/time.h>
-#include <linux/kernel_stat.h>
-#include <linux/wait.h>
-#include <linux/kthread.h>
-#include <linux/prefetch.h>
-#include <linux/delay.h>
-#include <linux/stop_machine.h>
-#include <linux/random.h>
-#include <linux/ftrace_event.h>
-#include <linux/suspend.h>
-
-#include "rcutree.h"
-#include <trace/events/rcu.h>
-
-#include "rcu.h"
-
-/* Data structures. */
-
-static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
-static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
-
-/*
- * In order to export the rcu_state name to the tracing tools, it
- * needs to be added in the __tracepoint_string section.
- * This requires defining a separate variable tp_<sname>_varname
- * that points to the string being used, and this will allow
- * the tracing userspace tools to be able to decipher the string
- * address to the matching string.
- */
-#define RCU_STATE_INITIALIZER(sname, sabbr, cr) \
-static char sname##_varname[] = #sname; \
-static const char *tp_##sname##_varname __used __tracepoint_string = sname##_varname; \
-struct rcu_state sname##_state = { \
- .level = { &sname##_state.node[0] }, \
- .call = cr, \
- .fqs_state = RCU_GP_IDLE, \
- .gpnum = 0UL - 300UL, \
- .completed = 0UL - 300UL, \
- .orphan_lock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.orphan_lock), \
- .orphan_nxttail = &sname##_state.orphan_nxtlist, \
- .orphan_donetail = &sname##_state.orphan_donelist, \
- .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
- .onoff_mutex = __MUTEX_INITIALIZER(sname##_state.onoff_mutex), \
- .name = sname##_varname, \
- .abbr = sabbr, \
-}; \
-DEFINE_PER_CPU(struct rcu_data, sname##_data)
-
-RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched);
-RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh);
-
-static struct rcu_state *rcu_state;
-LIST_HEAD(rcu_struct_flavors);
-
-/* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */
-static int rcu_fanout_leaf = CONFIG_RCU_FANOUT_LEAF;
-module_param(rcu_fanout_leaf, int, 0444);
-int rcu_num_lvls __read_mostly = RCU_NUM_LVLS;
-static int num_rcu_lvl[] = { /* Number of rcu_nodes at specified level. */
- NUM_RCU_LVL_0,
- NUM_RCU_LVL_1,
- NUM_RCU_LVL_2,
- NUM_RCU_LVL_3,
- NUM_RCU_LVL_4,
-};
-int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */
-
-/*
- * The rcu_scheduler_active variable transitions from zero to one just
- * before the first task is spawned. So when this variable is zero, RCU
- * can assume that there is but one task, allowing RCU to (for example)
- * optimize synchronize_sched() to a simple barrier(). When this variable
- * is one, RCU must actually do all the hard work required to detect real
- * grace periods. This variable is also used to suppress boot-time false
- * positives from lockdep-RCU error checking.
- */
-int rcu_scheduler_active __read_mostly;
-EXPORT_SYMBOL_GPL(rcu_scheduler_active);
-
-/*
- * The rcu_scheduler_fully_active variable transitions from zero to one
- * during the early_initcall() processing, which is after the scheduler
- * is capable of creating new tasks. So RCU processing (for example,
- * creating tasks for RCU priority boosting) must be delayed until after
- * rcu_scheduler_fully_active transitions from zero to one. We also
- * currently delay invocation of any RCU callbacks until after this point.
- *
- * It might later prove better for people registering RCU callbacks during
- * early boot to take responsibility for these callbacks, but one step at
- * a time.
- */
-static int rcu_scheduler_fully_active __read_mostly;
-
-#ifdef CONFIG_RCU_BOOST
-
-/*
- * Control variables for per-CPU and per-rcu_node kthreads. These
- * handle all flavors of RCU.
- */
-static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task);
-DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
-DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
-DEFINE_PER_CPU(char, rcu_cpu_has_work);
-
-#endif /* #ifdef CONFIG_RCU_BOOST */
-
-static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
-static void invoke_rcu_core(void);
-static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
-
-/*
- * Track the rcutorture test sequence number and the update version
- * number within a given test. The rcutorture_testseq is incremented
- * on every rcutorture module load and unload, so has an odd value
- * when a test is running. The rcutorture_vernum is set to zero
- * when rcutorture starts and is incremented on each rcutorture update.
- * These variables enable correlating rcutorture output with the
- * RCU tracing information.
- */
-unsigned long rcutorture_testseq;
-unsigned long rcutorture_vernum;
-
-/*
- * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s
- * permit this function to be invoked without holding the root rcu_node
- * structure's ->lock, but of course results can be subject to change.
- */
-static int rcu_gp_in_progress(struct rcu_state *rsp)
-{
- return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum);
-}
-
-/*
- * Note a quiescent state. Because we do not need to know
- * how many quiescent states passed, just if there was at least
- * one since the start of the grace period, this just sets a flag.
- * The caller must have disabled preemption.
- */
-void rcu_sched_qs(int cpu)
-{
- struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu);
-
- if (rdp->passed_quiesce == 0)
- trace_rcu_grace_period(TPS("rcu_sched"), rdp->gpnum, TPS("cpuqs"));
- rdp->passed_quiesce = 1;
-}
-
-void rcu_bh_qs(int cpu)
-{
- struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
-
- if (rdp->passed_quiesce == 0)
- trace_rcu_grace_period(TPS("rcu_bh"), rdp->gpnum, TPS("cpuqs"));
- rdp->passed_quiesce = 1;
-}
-
-/*
- * Note a context switch. This is a quiescent state for RCU-sched,
- * and requires special handling for preemptible RCU.
- * The caller must have disabled preemption.
- */
-void rcu_note_context_switch(int cpu)
-{
- trace_rcu_utilization(TPS("Start context switch"));
- rcu_sched_qs(cpu);
- rcu_preempt_note_context_switch(cpu);
- trace_rcu_utilization(TPS("End context switch"));
-}
-EXPORT_SYMBOL_GPL(rcu_note_context_switch);
-
-static DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
- .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE,
- .dynticks = ATOMIC_INIT(1),
-#ifdef CONFIG_NO_HZ_FULL_SYSIDLE
- .dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE,
- .dynticks_idle = ATOMIC_INIT(1),
-#endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
-};
-
-static long blimit = 10; /* Maximum callbacks per rcu_do_batch. */
-static long qhimark = 10000; /* If this many pending, ignore blimit. */
-static long qlowmark = 100; /* Once only this many pending, use blimit. */
-
-module_param(blimit, long, 0444);
-module_param(qhimark, long, 0444);
-module_param(qlowmark, long, 0444);
-
-static ulong jiffies_till_first_fqs = ULONG_MAX;
-static ulong jiffies_till_next_fqs = ULONG_MAX;
-
-module_param(jiffies_till_first_fqs, ulong, 0644);
-module_param(jiffies_till_next_fqs, ulong, 0644);
-
-static void rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
- struct rcu_data *rdp);
-static void force_qs_rnp(struct rcu_state *rsp,
- int (*f)(struct rcu_data *rsp, bool *isidle,
- unsigned long *maxj),
- bool *isidle, unsigned long *maxj);
-static void force_quiescent_state(struct rcu_state *rsp);
-static int rcu_pending(int cpu);
-
-/*
- * Return the number of RCU-sched batches processed thus far for debug & stats.
- */
-long rcu_batches_completed_sched(void)
-{
- return rcu_sched_state.completed;
-}
-EXPORT_SYMBOL_GPL(rcu_batches_completed_sched);
-
-/*
- * Return the number of RCU BH batches processed thus far for debug & stats.
- */
-long rcu_batches_completed_bh(void)
-{
- return rcu_bh_state.completed;
-}
-EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
-
-/*
- * Force a quiescent state for RCU BH.
- */
-void rcu_bh_force_quiescent_state(void)
-{
- force_quiescent_state(&rcu_bh_state);
-}
-EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
-
-/*
- * Record the number of times rcutorture tests have been initiated and
- * terminated. This information allows the debugfs tracing stats to be
- * correlated to the rcutorture messages, even when the rcutorture module
- * is being repeatedly loaded and unloaded. In other words, we cannot
- * store this state in rcutorture itself.
- */
-void rcutorture_record_test_transition(void)
-{
- rcutorture_testseq++;
- rcutorture_vernum = 0;
-}
-EXPORT_SYMBOL_GPL(rcutorture_record_test_transition);
-
-/*
- * Record the number of writer passes through the current rcutorture test.
- * This is also used to correlate debugfs tracing stats with the rcutorture
- * messages.
- */
-void rcutorture_record_progress(unsigned long vernum)
-{
- rcutorture_vernum++;
-}
-EXPORT_SYMBOL_GPL(rcutorture_record_progress);
-
-/*
- * Force a quiescent state for RCU-sched.
- */
-void rcu_sched_force_quiescent_state(void)
-{
- force_quiescent_state(&rcu_sched_state);
-}
-EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state);
-
-/*
- * Does the CPU have callbacks ready to be invoked?
- */
-static int
-cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp)
-{
- return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL] &&
- rdp->nxttail[RCU_DONE_TAIL] != NULL;
-}
-
-/*
- * Does the current CPU require a not-yet-started grace period?
- * The caller must have disabled interrupts to prevent races with
- * normal callback registry.
- */
-static int
-cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
-{
- int i;
-
- if (rcu_gp_in_progress(rsp))
- return 0; /* No, a grace period is already in progress. */
- if (rcu_nocb_needs_gp(rsp))
- return 1; /* Yes, a no-CBs CPU needs one. */
- if (!rdp->nxttail[RCU_NEXT_TAIL])
- return 0; /* No, this is a no-CBs (or offline) CPU. */
- if (*rdp->nxttail[RCU_NEXT_READY_TAIL])
- return 1; /* Yes, this CPU has newly registered callbacks. */
- for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++)
- if (rdp->nxttail[i - 1] != rdp->nxttail[i] &&
- ULONG_CMP_LT(ACCESS_ONCE(rsp->completed),
- rdp->nxtcompleted[i]))
- return 1; /* Yes, CBs for future grace period. */
- return 0; /* No grace period needed. */
-}
-
-/*
- * Return the root node of the specified rcu_state structure.
- */
-static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
-{
- return &rsp->node[0];
-}
-
-/*
- * rcu_eqs_enter_common - current CPU is moving towards extended quiescent state
- *
- * If the new value of the ->dynticks_nesting counter now is zero,
- * we really have entered idle, and must do the appropriate accounting.
- * The caller must have disabled interrupts.
- */
-static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval,
- bool user)
-{
- trace_rcu_dyntick(TPS("Start"), oldval, rdtp->dynticks_nesting);
- if (!user && !is_idle_task(current)) {
- struct task_struct *idle __maybe_unused =
- idle_task(smp_processor_id());
-
- trace_rcu_dyntick(TPS("Error on entry: not idle task"), oldval, 0);
- ftrace_dump(DUMP_ORIG);
- WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
- current->pid, current->comm,
- idle->pid, idle->comm); /* must be idle task! */
- }
- rcu_prepare_for_idle(smp_processor_id());
- /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
- smp_mb__before_atomic_inc(); /* See above. */
- atomic_inc(&rdtp->dynticks);
- smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */
- WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
-
- /*
- * It is illegal to enter an extended quiescent state while
- * in an RCU read-side critical section.
- */
- rcu_lockdep_assert(!lock_is_held(&rcu_lock_map),
- "Illegal idle entry in RCU read-side critical section.");
- rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map),
- "Illegal idle entry in RCU-bh read-side critical section.");
- rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map),
- "Illegal idle entry in RCU-sched read-side critical section.");
-}
-
-/*
- * Enter an RCU extended quiescent state, which can be either the
- * idle loop or adaptive-tickless usermode execution.
- */
-static void rcu_eqs_enter(bool user)
-{
- long long oldval;
- struct rcu_dynticks *rdtp;
-
- rdtp = this_cpu_ptr(&rcu_dynticks);
- oldval = rdtp->dynticks_nesting;
- WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0);
- if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE)
- rdtp->dynticks_nesting = 0;
- else
- rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE;
- rcu_eqs_enter_common(rdtp, oldval, user);
-}
-
-/**
- * rcu_idle_enter - inform RCU that current CPU is entering idle
- *
- * Enter idle mode, in other words, -leave- the mode in which RCU
- * read-side critical sections can occur. (Though RCU read-side
- * critical sections can occur in irq handlers in idle, a possibility
- * handled by irq_enter() and irq_exit().)
- *
- * We crowbar the ->dynticks_nesting field to zero to allow for
- * the possibility of usermode upcalls having messed up our count
- * of interrupt nesting level during the prior busy period.
- */
-void rcu_idle_enter(void)
-{
- unsigned long flags;
-
- local_irq_save(flags);
- rcu_eqs_enter(false);
- rcu_sysidle_enter(this_cpu_ptr(&rcu_dynticks), 0);
- local_irq_restore(flags);
-}
-EXPORT_SYMBOL_GPL(rcu_idle_enter);
-
-#ifdef CONFIG_RCU_USER_QS
-/**
- * rcu_user_enter - inform RCU that we are resuming userspace.
- *
- * Enter RCU idle mode right before resuming userspace. No use of RCU
- * is permitted between this call and rcu_user_exit(). This way the
- * CPU doesn't need to maintain the tick for RCU maintenance purposes
- * when the CPU runs in userspace.
- */
-void rcu_user_enter(void)
-{
- rcu_eqs_enter(1);
-}
-#endif /* CONFIG_RCU_USER_QS */
-
-/**
- * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
- *
- * Exit from an interrupt handler, which might possibly result in entering
- * idle mode, in other words, leaving the mode in which read-side critical
- * sections can occur.
- *
- * This code assumes that the idle loop never does anything that might
- * result in unbalanced calls to irq_enter() and irq_exit(). If your
- * architecture violates this assumption, RCU will give you what you
- * deserve, good and hard. But very infrequently and irreproducibly.
- *
- * Use things like work queues to work around this limitation.
- *
- * You have been warned.
- */
-void rcu_irq_exit(void)
-{
- unsigned long flags;
- long long oldval;
- struct rcu_dynticks *rdtp;
-
- local_irq_save(flags);
- rdtp = this_cpu_ptr(&rcu_dynticks);
- oldval = rdtp->dynticks_nesting;
- rdtp->dynticks_nesting--;
- WARN_ON_ONCE(rdtp->dynticks_nesting < 0);
- if (rdtp->dynticks_nesting)
- trace_rcu_dyntick(TPS("--="), oldval, rdtp->dynticks_nesting);
- else
- rcu_eqs_enter_common(rdtp, oldval, true);
- rcu_sysidle_enter(rdtp, 1);
- local_irq_restore(flags);
-}
-
-/*
- * rcu_eqs_exit_common - current CPU moving away from extended quiescent state
- *
- * If the new value of the ->dynticks_nesting counter was previously zero,
- * we really have exited idle, and must do the appropriate accounting.
- * The caller must have disabled interrupts.
- */
-static void rcu_eqs_exit_common(struct rcu_dynticks *rdtp, long long oldval,
- int user)
-{
- smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */
- atomic_inc(&rdtp->dynticks);
- /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
- smp_mb__after_atomic_inc(); /* See above. */
- WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
- rcu_cleanup_after_idle(smp_processor_id());
- trace_rcu_dyntick(TPS("End"), oldval, rdtp->dynticks_nesting);
- if (!user && !is_idle_task(current)) {
- struct task_struct *idle __maybe_unused =
- idle_task(smp_processor_id());
-
- trace_rcu_dyntick(TPS("Error on exit: not idle task"),
- oldval, rdtp->dynticks_nesting);
- ftrace_dump(DUMP_ORIG);
- WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
- current->pid, current->comm,
- idle->pid, idle->comm); /* must be idle task! */
- }
-}
-
-/*
- * Exit an RCU extended quiescent state, which can be either the
- * idle loop or adaptive-tickless usermode execution.
- */
-static void rcu_eqs_exit(bool user)
-{
- struct rcu_dynticks *rdtp;
- long long oldval;
-
- rdtp = this_cpu_ptr(&rcu_dynticks);
- oldval = rdtp->dynticks_nesting;
- WARN_ON_ONCE(oldval < 0);
- if (oldval & DYNTICK_TASK_NEST_MASK)
- rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE;
- else
- rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
- rcu_eqs_exit_common(rdtp, oldval, user);
-}
-
-/**
- * rcu_idle_exit - inform RCU that current CPU is leaving idle
- *
- * Exit idle mode, in other words, -enter- the mode in which RCU
- * read-side critical sections can occur.
- *
- * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to
- * allow for the possibility of usermode upcalls messing up our count
- * of interrupt nesting level during the busy period that is just
- * now starting.
- */
-void rcu_idle_exit(void)
-{
- unsigned long flags;
-
- local_irq_save(flags);
- rcu_eqs_exit(false);
- rcu_sysidle_exit(this_cpu_ptr(&rcu_dynticks), 0);
- local_irq_restore(flags);
-}
-EXPORT_SYMBOL_GPL(rcu_idle_exit);
-
-#ifdef CONFIG_RCU_USER_QS
-/**
- * rcu_user_exit - inform RCU that we are exiting userspace.
- *
- * Exit RCU idle mode while entering the kernel because it can
- * run a RCU read side critical section anytime.
- */
-void rcu_user_exit(void)
-{
- rcu_eqs_exit(1);
-}
-#endif /* CONFIG_RCU_USER_QS */
-
-/**
- * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle
- *
- * Enter an interrupt handler, which might possibly result in exiting
- * idle mode, in other words, entering the mode in which read-side critical
- * sections can occur.
- *
- * Note that the Linux kernel is fully capable of entering an interrupt
- * handler that it never exits, for example when doing upcalls to
- * user mode! This code assumes that the idle loop never does upcalls to
- * user mode. If your architecture does do upcalls from the idle loop (or
- * does anything else that results in unbalanced calls to the irq_enter()
- * and irq_exit() functions), RCU will give you what you deserve, good
- * and hard. But very infrequently and irreproducibly.
- *
- * Use things like work queues to work around this limitation.
- *
- * You have been warned.
- */
-void rcu_irq_enter(void)
-{
- unsigned long flags;
- struct rcu_dynticks *rdtp;
- long long oldval;
-
- local_irq_save(flags);
- rdtp = this_cpu_ptr(&rcu_dynticks);
- oldval = rdtp->dynticks_nesting;
- rdtp->dynticks_nesting++;
- WARN_ON_ONCE(rdtp->dynticks_nesting == 0);
- if (oldval)
- trace_rcu_dyntick(TPS("++="), oldval, rdtp->dynticks_nesting);
- else
- rcu_eqs_exit_common(rdtp, oldval, true);
- rcu_sysidle_exit(rdtp, 1);
- local_irq_restore(flags);
-}
-
-/**
- * rcu_nmi_enter - inform RCU of entry to NMI context
- *
- * If the CPU was idle with dynamic ticks active, and there is no
- * irq handler running, this updates rdtp->dynticks_nmi to let the
- * RCU grace-period handling know that the CPU is active.
- */
-void rcu_nmi_enter(void)
-{
- struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
-
- if (rdtp->dynticks_nmi_nesting == 0 &&
- (atomic_read(&rdtp->dynticks) & 0x1))
- return;
- rdtp->dynticks_nmi_nesting++;
- smp_mb__before_atomic_inc(); /* Force delay from prior write. */
- atomic_inc(&rdtp->dynticks);
- /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
- smp_mb__after_atomic_inc(); /* See above. */
- WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
-}
-
-/**
- * rcu_nmi_exit - inform RCU of exit from NMI context
- *
- * If the CPU was idle with dynamic ticks active, and there is no
- * irq handler running, this updates rdtp->dynticks_nmi to let the
- * RCU grace-period handling know that the CPU is no longer active.
- */
-void rcu_nmi_exit(void)
-{
- struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
-
- if (rdtp->dynticks_nmi_nesting == 0 ||
- --rdtp->dynticks_nmi_nesting != 0)
- return;
- /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
- smp_mb__before_atomic_inc(); /* See above. */
- atomic_inc(&rdtp->dynticks);
- smp_mb__after_atomic_inc(); /* Force delay to next write. */
- WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
-}
-
-/**
- * __rcu_is_watching - are RCU read-side critical sections safe?
- *
- * Return true if RCU is watching the running CPU, which means that
- * this CPU can safely enter RCU read-side critical sections. Unlike
- * rcu_is_watching(), the caller of __rcu_is_watching() must have at
- * least disabled preemption.
- */
-bool __rcu_is_watching(void)
-{
- return atomic_read(this_cpu_ptr(&rcu_dynticks.dynticks)) & 0x1;
-}
-
-/**
- * rcu_is_watching - see if RCU thinks that the current CPU is idle
- *
- * If the current CPU is in its idle loop and is neither in an interrupt
- * or NMI handler, return true.
- */
-bool rcu_is_watching(void)
-{
- int ret;
-
- preempt_disable();
- ret = __rcu_is_watching();
- preempt_enable();
- return ret;
-}
-EXPORT_SYMBOL_GPL(rcu_is_watching);
-
-#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU)
-
-/*
- * Is the current CPU online? Disable preemption to avoid false positives
- * that could otherwise happen due to the current CPU number being sampled,
- * this task being preempted, its old CPU being taken offline, resuming
- * on some other CPU, then determining that its old CPU is now offline.
- * It is OK to use RCU on an offline processor during initial boot, hence
- * the check for rcu_scheduler_fully_active. Note also that it is OK
- * for a CPU coming online to use RCU for one jiffy prior to marking itself
- * online in the cpu_online_mask. Similarly, it is OK for a CPU going
- * offline to continue to use RCU for one jiffy after marking itself
- * offline in the cpu_online_mask. This leniency is necessary given the
- * non-atomic nature of the online and offline processing, for example,
- * the fact that a CPU enters the scheduler after completing the CPU_DYING
- * notifiers.
- *
- * This is also why RCU internally marks CPUs online during the
- * CPU_UP_PREPARE phase and offline during the CPU_DEAD phase.
- *
- * Disable checking if in an NMI handler because we cannot safely report
- * errors from NMI handlers anyway.
- */
-bool rcu_lockdep_current_cpu_online(void)
-{
- struct rcu_data *rdp;
- struct rcu_node *rnp;
- bool ret;
-
- if (in_nmi())
- return 1;
- preempt_disable();
- rdp = this_cpu_ptr(&rcu_sched_data);
- rnp = rdp->mynode;
- ret = (rdp->grpmask & rnp->qsmaskinit) ||
- !rcu_scheduler_fully_active;
- preempt_enable();
- return ret;
-}
-EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online);
-
-#endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */
-
-/**
- * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle
- *
- * If the current CPU is idle or running at a first-level (not nested)
- * interrupt from idle, return true. The caller must have at least
- * disabled preemption.
- */
-static int rcu_is_cpu_rrupt_from_idle(void)
-{
- return __this_cpu_read(rcu_dynticks.dynticks_nesting) <= 1;
-}
-
-/*
- * Snapshot the specified CPU's dynticks counter so that we can later
- * credit them with an implicit quiescent state. Return 1 if this CPU
- * is in dynticks idle mode, which is an extended quiescent state.
- */
-static int dyntick_save_progress_counter(struct rcu_data *rdp,
- bool *isidle, unsigned long *maxj)
-{
- rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks);
- rcu_sysidle_check_cpu(rdp, isidle, maxj);
- return (rdp->dynticks_snap & 0x1) == 0;
-}
-
-/*
- * Return true if the specified CPU has passed through a quiescent
- * state by virtue of being in or having passed through an dynticks
- * idle state since the last call to dyntick_save_progress_counter()
- * for this same CPU, or by virtue of having been offline.
- */
-static int rcu_implicit_dynticks_qs(struct rcu_data *rdp,
- bool *isidle, unsigned long *maxj)
-{
- unsigned int curr;
- unsigned int snap;
-
- curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks);
- snap = (unsigned int)rdp->dynticks_snap;
-
- /*
- * If the CPU passed through or entered a dynticks idle phase with
- * no active irq/NMI handlers, then we can safely pretend that the CPU
- * already acknowledged the request to pass through a quiescent
- * state. Either way, that CPU cannot possibly be in an RCU
- * read-side critical section that started before the beginning
- * of the current RCU grace period.
- */
- if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) {
- trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti"));
- rdp->dynticks_fqs++;
- return 1;
- }
-
- /*
- * Check for the CPU being offline, but only if the grace period
- * is old enough. We don't need to worry about the CPU changing
- * state: If we see it offline even once, it has been through a
- * quiescent state.
- *
- * The reason for insisting that the grace period be at least
- * one jiffy old is that CPUs that are not quite online and that
- * have just gone offline can still execute RCU read-side critical
- * sections.
- */
- if (ULONG_CMP_GE(rdp->rsp->gp_start + 2, jiffies))
- return 0; /* Grace period is not old enough. */
- barrier();
- if (cpu_is_offline(rdp->cpu)) {
- trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("ofl"));
- rdp->offline_fqs++;
- return 1;
- }
-
- /*
- * There is a possibility that a CPU in adaptive-ticks state
- * might run in the kernel with the scheduling-clock tick disabled
- * for an extended time period. Invoke rcu_kick_nohz_cpu() to
- * force the CPU to restart the scheduling-clock tick in this
- * CPU is in this state.
- */
- rcu_kick_nohz_cpu(rdp->cpu);
-
- return 0;
-}
-
-static void record_gp_stall_check_time(struct rcu_state *rsp)
-{
- unsigned long j = ACCESS_ONCE(jiffies);
-
- rsp->gp_start = j;
- smp_wmb(); /* Record start time before stall time. */
- rsp->jiffies_stall = j + rcu_jiffies_till_stall_check();
-}
-
-/*
- * Dump stacks of all tasks running on stalled CPUs. This is a fallback
- * for architectures that do not implement trigger_all_cpu_backtrace().
- * The NMI-triggered stack traces are more accurate because they are
- * printed by the target CPU.
- */
-static void rcu_dump_cpu_stacks(struct rcu_state *rsp)
-{
- int cpu;
- unsigned long flags;
- struct rcu_node *rnp;
-
- rcu_for_each_leaf_node(rsp, rnp) {
- raw_spin_lock_irqsave(&rnp->lock, flags);
- if (rnp->qsmask != 0) {
- for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
- if (rnp->qsmask & (1UL << cpu))
- dump_cpu_task(rnp->grplo + cpu);
- }
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- }
-}
-
-static void print_other_cpu_stall(struct rcu_state *rsp)
-{
- int cpu;
- long delta;
- unsigned long flags;
- int ndetected = 0;
- struct rcu_node *rnp = rcu_get_root(rsp);
- long totqlen = 0;
-
- /* Only let one CPU complain about others per time interval. */
-
- raw_spin_lock_irqsave(&rnp->lock, flags);
- delta = jiffies - rsp->jiffies_stall;
- if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) {
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- return;
- }
- rsp->jiffies_stall = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
-
- /*
- * OK, time to rat on our buddy...
- * See Documentation/RCU/stallwarn.txt for info on how to debug
- * RCU CPU stall warnings.
- */
- pr_err("INFO: %s detected stalls on CPUs/tasks:",
- rsp->name);
- print_cpu_stall_info_begin();
- rcu_for_each_leaf_node(rsp, rnp) {
- raw_spin_lock_irqsave(&rnp->lock, flags);
- ndetected += rcu_print_task_stall(rnp);
- if (rnp->qsmask != 0) {
- for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
- if (rnp->qsmask & (1UL << cpu)) {
- print_cpu_stall_info(rsp,
- rnp->grplo + cpu);
- ndetected++;
- }
- }
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- }
-
- /*
- * Now rat on any tasks that got kicked up to the root rcu_node
- * due to CPU offlining.
- */
- rnp = rcu_get_root(rsp);
- raw_spin_lock_irqsave(&rnp->lock, flags);
- ndetected += rcu_print_task_stall(rnp);
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
-
- print_cpu_stall_info_end();
- for_each_possible_cpu(cpu)
- totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen;
- pr_cont("(detected by %d, t=%ld jiffies, g=%lu, c=%lu, q=%lu)\n",
- smp_processor_id(), (long)(jiffies - rsp->gp_start),
- rsp->gpnum, rsp->completed, totqlen);
- if (ndetected == 0)
- pr_err("INFO: Stall ended before state dump start\n");
- else if (!trigger_all_cpu_backtrace())
- rcu_dump_cpu_stacks(rsp);
-
- /* Complain about tasks blocking the grace period. */
-
- rcu_print_detail_task_stall(rsp);
-
- force_quiescent_state(rsp); /* Kick them all. */
-}
-
-static void print_cpu_stall(struct rcu_state *rsp)
-{
- int cpu;
- unsigned long flags;
- struct rcu_node *rnp = rcu_get_root(rsp);
- long totqlen = 0;
-
- /*
- * OK, time to rat on ourselves...
- * See Documentation/RCU/stallwarn.txt for info on how to debug
- * RCU CPU stall warnings.
- */
- pr_err("INFO: %s self-detected stall on CPU", rsp->name);
- print_cpu_stall_info_begin();
- print_cpu_stall_info(rsp, smp_processor_id());
- print_cpu_stall_info_end();
- for_each_possible_cpu(cpu)
- totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen;
- pr_cont(" (t=%lu jiffies g=%lu c=%lu q=%lu)\n",
- jiffies - rsp->gp_start, rsp->gpnum, rsp->completed, totqlen);
- if (!trigger_all_cpu_backtrace())
- dump_stack();
-
- raw_spin_lock_irqsave(&rnp->lock, flags);
- if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall))
- rsp->jiffies_stall = jiffies +
- 3 * rcu_jiffies_till_stall_check() + 3;
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
-
- set_need_resched(); /* kick ourselves to get things going. */
-}
-
-static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
-{
- unsigned long completed;
- unsigned long gpnum;
- unsigned long gps;
- unsigned long j;
- unsigned long js;
- struct rcu_node *rnp;
-
- if (rcu_cpu_stall_suppress || !rcu_gp_in_progress(rsp))
- return;
- j = ACCESS_ONCE(jiffies);
-
- /*
- * Lots of memory barriers to reject false positives.
- *
- * The idea is to pick up rsp->gpnum, then rsp->jiffies_stall,
- * then rsp->gp_start, and finally rsp->completed. These values
- * are updated in the opposite order with memory barriers (or
- * equivalent) during grace-period initialization and cleanup.
- * Now, a false positive can occur if we get an new value of
- * rsp->gp_start and a old value of rsp->jiffies_stall. But given
- * the memory barriers, the only way that this can happen is if one
- * grace period ends and another starts between these two fetches.
- * Detect this by comparing rsp->completed with the previous fetch
- * from rsp->gpnum.
- *
- * Given this check, comparisons of jiffies, rsp->jiffies_stall,
- * and rsp->gp_start suffice to forestall false positives.
- */
- gpnum = ACCESS_ONCE(rsp->gpnum);
- smp_rmb(); /* Pick up ->gpnum first... */
- js = ACCESS_ONCE(rsp->jiffies_stall);
- smp_rmb(); /* ...then ->jiffies_stall before the rest... */
- gps = ACCESS_ONCE(rsp->gp_start);
- smp_rmb(); /* ...and finally ->gp_start before ->completed. */
- completed = ACCESS_ONCE(rsp->completed);
- if (ULONG_CMP_GE(completed, gpnum) ||
- ULONG_CMP_LT(j, js) ||
- ULONG_CMP_GE(gps, js))
- return; /* No stall or GP completed since entering function. */
- rnp = rdp->mynode;
- if (rcu_gp_in_progress(rsp) &&
- (ACCESS_ONCE(rnp->qsmask) & rdp->grpmask)) {
-
- /* We haven't checked in, so go dump stack. */
- print_cpu_stall(rsp);
-
- } else if (rcu_gp_in_progress(rsp) &&
- ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) {
-
- /* They had a few time units to dump stack, so complain. */
- print_other_cpu_stall(rsp);
- }
-}
-
-/**
- * rcu_cpu_stall_reset - prevent further stall warnings in current grace period
- *
- * Set the stall-warning timeout way off into the future, thus preventing
- * any RCU CPU stall-warning messages from appearing in the current set of
- * RCU grace periods.
- *
- * The caller must disable hard irqs.
- */
-void rcu_cpu_stall_reset(void)
-{
- struct rcu_state *rsp;
-
- for_each_rcu_flavor(rsp)
- rsp->jiffies_stall = jiffies + ULONG_MAX / 2;
-}
-
-/*
- * Initialize the specified rcu_data structure's callback list to empty.
- */
-static void init_callback_list(struct rcu_data *rdp)
-{
- int i;
-
- if (init_nocb_callback_list(rdp))
- return;
- rdp->nxtlist = NULL;
- for (i = 0; i < RCU_NEXT_SIZE; i++)
- rdp->nxttail[i] = &rdp->nxtlist;
-}
-
-/*
- * Determine the value that ->completed will have at the end of the
- * next subsequent grace period. This is used to tag callbacks so that
- * a CPU can invoke callbacks in a timely fashion even if that CPU has
- * been dyntick-idle for an extended period with callbacks under the
- * influence of RCU_FAST_NO_HZ.
- *
- * The caller must hold rnp->lock with interrupts disabled.
- */
-static unsigned long rcu_cbs_completed(struct rcu_state *rsp,
- struct rcu_node *rnp)
-{
- /*
- * If RCU is idle, we just wait for the next grace period.
- * But we can only be sure that RCU is idle if we are looking
- * at the root rcu_node structure -- otherwise, a new grace
- * period might have started, but just not yet gotten around
- * to initializing the current non-root rcu_node structure.
- */
- if (rcu_get_root(rsp) == rnp && rnp->gpnum == rnp->completed)
- return rnp->completed + 1;
-
- /*
- * Otherwise, wait for a possible partial grace period and
- * then the subsequent full grace period.
- */
- return rnp->completed + 2;
-}
-
-/*
- * Trace-event helper function for rcu_start_future_gp() and
- * rcu_nocb_wait_gp().
- */
-static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
- unsigned long c, const char *s)
-{
- trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum,
- rnp->completed, c, rnp->level,
- rnp->grplo, rnp->grphi, s);
-}
-
-/*
- * Start some future grace period, as needed to handle newly arrived
- * callbacks. The required future grace periods are recorded in each
- * rcu_node structure's ->need_future_gp field.
- *
- * The caller must hold the specified rcu_node structure's ->lock.
- */
-static unsigned long __maybe_unused
-rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp)
-{
- unsigned long c;
- int i;
- struct rcu_node *rnp_root = rcu_get_root(rdp->rsp);
-
- /*
- * Pick up grace-period number for new callbacks. If this
- * grace period is already marked as needed, return to the caller.
- */
- c = rcu_cbs_completed(rdp->rsp, rnp);
- trace_rcu_future_gp(rnp, rdp, c, TPS("Startleaf"));
- if (rnp->need_future_gp[c & 0x1]) {
- trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartleaf"));
- return c;
- }
-
- /*
- * If either this rcu_node structure or the root rcu_node structure
- * believe that a grace period is in progress, then we must wait
- * for the one following, which is in "c". Because our request
- * will be noticed at the end of the current grace period, we don't
- * need to explicitly start one.
- */
- if (rnp->gpnum != rnp->completed ||
- ACCESS_ONCE(rnp->gpnum) != ACCESS_ONCE(rnp->completed)) {
- rnp->need_future_gp[c & 0x1]++;
- trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleaf"));
- return c;
- }
-
- /*
- * There might be no grace period in progress. If we don't already
- * hold it, acquire the root rcu_node structure's lock in order to
- * start one (if needed).
- */
- if (rnp != rnp_root)
- raw_spin_lock(&rnp_root->lock);
-
- /*
- * Get a new grace-period number. If there really is no grace
- * period in progress, it will be smaller than the one we obtained
- * earlier. Adjust callbacks as needed. Note that even no-CBs
- * CPUs have a ->nxtcompleted[] array, so no no-CBs checks needed.
- */
- c = rcu_cbs_completed(rdp->rsp, rnp_root);
- for (i = RCU_DONE_TAIL; i < RCU_NEXT_TAIL; i++)
- if (ULONG_CMP_LT(c, rdp->nxtcompleted[i]))
- rdp->nxtcompleted[i] = c;
-
- /*
- * If the needed for the required grace period is already
- * recorded, trace and leave.
- */
- if (rnp_root->need_future_gp[c & 0x1]) {
- trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartedroot"));
- goto unlock_out;
- }
-
- /* Record the need for the future grace period. */
- rnp_root->need_future_gp[c & 0x1]++;
-
- /* If a grace period is not already in progress, start one. */
- if (rnp_root->gpnum != rnp_root->completed) {
- trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleafroot"));
- } else {
- trace_rcu_future_gp(rnp, rdp, c, TPS("Startedroot"));
- rcu_start_gp_advanced(rdp->rsp, rnp_root, rdp);
- }
-unlock_out:
- if (rnp != rnp_root)
- raw_spin_unlock(&rnp_root->lock);
- return c;
-}
-
-/*
- * Clean up any old requests for the just-ended grace period. Also return
- * whether any additional grace periods have been requested. Also invoke
- * rcu_nocb_gp_cleanup() in order to wake up any no-callbacks kthreads
- * waiting for this grace period to complete.
- */
-static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
-{
- int c = rnp->completed;
- int needmore;
- struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
-
- rcu_nocb_gp_cleanup(rsp, rnp);
- rnp->need_future_gp[c & 0x1] = 0;
- needmore = rnp->need_future_gp[(c + 1) & 0x1];
- trace_rcu_future_gp(rnp, rdp, c,
- needmore ? TPS("CleanupMore") : TPS("Cleanup"));
- return needmore;
-}
-
-/*
- * If there is room, assign a ->completed number to any callbacks on
- * this CPU that have not already been assigned. Also accelerate any
- * callbacks that were previously assigned a ->completed number that has
- * since proven to be too conservative, which can happen if callbacks get
- * assigned a ->completed number while RCU is idle, but with reference to
- * a non-root rcu_node structure. This function is idempotent, so it does
- * not hurt to call it repeatedly.
- *
- * The caller must hold rnp->lock with interrupts disabled.
- */
-static void rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
- struct rcu_data *rdp)
-{
- unsigned long c;
- int i;
-
- /* If the CPU has no callbacks, nothing to do. */
- if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL])
- return;
-
- /*
- * Starting from the sublist containing the callbacks most
- * recently assigned a ->completed number and working down, find the
- * first sublist that is not assignable to an upcoming grace period.
- * Such a sublist has something in it (first two tests) and has
- * a ->completed number assigned that will complete sooner than
- * the ->completed number for newly arrived callbacks (last test).
- *
- * The key point is that any later sublist can be assigned the
- * same ->completed number as the newly arrived callbacks, which
- * means that the callbacks in any of these later sublist can be
- * grouped into a single sublist, whether or not they have already
- * been assigned a ->completed number.
- */
- c = rcu_cbs_completed(rsp, rnp);
- for (i = RCU_NEXT_TAIL - 1; i > RCU_DONE_TAIL; i--)
- if (rdp->nxttail[i] != rdp->nxttail[i - 1] &&
- !ULONG_CMP_GE(rdp->nxtcompleted[i], c))
- break;
-
- /*
- * If there are no sublist for unassigned callbacks, leave.
- * At the same time, advance "i" one sublist, so that "i" will
- * index into the sublist where all the remaining callbacks should
- * be grouped into.
- */
- if (++i >= RCU_NEXT_TAIL)
- return;
-
- /*
- * Assign all subsequent callbacks' ->completed number to the next
- * full grace period and group them all in the sublist initially
- * indexed by "i".
- */
- for (; i <= RCU_NEXT_TAIL; i++) {
- rdp->nxttail[i] = rdp->nxttail[RCU_NEXT_TAIL];
- rdp->nxtcompleted[i] = c;
- }
- /* Record any needed additional grace periods. */
- rcu_start_future_gp(rnp, rdp);
-
- /* Trace depending on how much we were able to accelerate. */
- if (!*rdp->nxttail[RCU_WAIT_TAIL])
- trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccWaitCB"));
- else
- trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccReadyCB"));
-}
-
-/*
- * Move any callbacks whose grace period has completed to the
- * RCU_DONE_TAIL sublist, then compact the remaining sublists and
- * assign ->completed numbers to any callbacks in the RCU_NEXT_TAIL
- * sublist. This function is idempotent, so it does not hurt to
- * invoke it repeatedly. As long as it is not invoked -too- often...
- *
- * The caller must hold rnp->lock with interrupts disabled.
- */
-static void rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
- struct rcu_data *rdp)
-{
- int i, j;
-
- /* If the CPU has no callbacks, nothing to do. */
- if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL])
- return;
-
- /*
- * Find all callbacks whose ->completed numbers indicate that they
- * are ready to invoke, and put them into the RCU_DONE_TAIL sublist.
- */
- for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) {
- if (ULONG_CMP_LT(rnp->completed, rdp->nxtcompleted[i]))
- break;
- rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[i];
- }
- /* Clean up any sublist tail pointers that were misordered above. */
- for (j = RCU_WAIT_TAIL; j < i; j++)
- rdp->nxttail[j] = rdp->nxttail[RCU_DONE_TAIL];
-
- /* Copy down callbacks to fill in empty sublists. */
- for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) {
- if (rdp->nxttail[j] == rdp->nxttail[RCU_NEXT_TAIL])
- break;
- rdp->nxttail[j] = rdp->nxttail[i];
- rdp->nxtcompleted[j] = rdp->nxtcompleted[i];
- }
-
- /* Classify any remaining callbacks. */
- rcu_accelerate_cbs(rsp, rnp, rdp);
-}
-
-/*
- * Update CPU-local rcu_data state to record the beginnings and ends of
- * grace periods. The caller must hold the ->lock of the leaf rcu_node
- * structure corresponding to the current CPU, and must have irqs disabled.
- */
-static void __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
-{
- /* Handle the ends of any preceding grace periods first. */
- if (rdp->completed == rnp->completed) {
-
- /* No grace period end, so just accelerate recent callbacks. */
- rcu_accelerate_cbs(rsp, rnp, rdp);
-
- } else {
-
- /* Advance callbacks. */
- rcu_advance_cbs(rsp, rnp, rdp);
-
- /* Remember that we saw this grace-period completion. */
- rdp->completed = rnp->completed;
- trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuend"));
- }
-
- if (rdp->gpnum != rnp->gpnum) {
- /*
- * If the current grace period is waiting for this CPU,
- * set up to detect a quiescent state, otherwise don't
- * go looking for one.
- */
- rdp->gpnum = rnp->gpnum;
- trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpustart"));
- rdp->passed_quiesce = 0;
- rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask);
- zero_cpu_stall_ticks(rdp);
- }
-}
-
-static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp)
-{
- unsigned long flags;
- struct rcu_node *rnp;
-
- local_irq_save(flags);
- rnp = rdp->mynode;
- if ((rdp->gpnum == ACCESS_ONCE(rnp->gpnum) &&
- rdp->completed == ACCESS_ONCE(rnp->completed)) || /* w/out lock. */
- !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
- local_irq_restore(flags);
- return;
- }
- __note_gp_changes(rsp, rnp, rdp);
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
-}
-
-/*
- * Initialize a new grace period. Return 0 if no grace period required.
- */
-static int rcu_gp_init(struct rcu_state *rsp)
-{
- struct rcu_data *rdp;
- struct rcu_node *rnp = rcu_get_root(rsp);
-
- rcu_bind_gp_kthread();
- raw_spin_lock_irq(&rnp->lock);
- if (rsp->gp_flags == 0) {
- /* Spurious wakeup, tell caller to go back to sleep. */
- raw_spin_unlock_irq(&rnp->lock);
- return 0;
- }
- rsp->gp_flags = 0; /* Clear all flags: New grace period. */
-
- if (WARN_ON_ONCE(rcu_gp_in_progress(rsp))) {
- /*
- * Grace period already in progress, don't start another.
- * Not supposed to be able to happen.
- */
- raw_spin_unlock_irq(&rnp->lock);
- return 0;
- }
-
- /* Advance to a new grace period and initialize state. */
- record_gp_stall_check_time(rsp);
- smp_wmb(); /* Record GP times before starting GP. */
- rsp->gpnum++;
- trace_rcu_grace_period(rsp->name, rsp->gpnum, TPS("start"));
- raw_spin_unlock_irq(&rnp->lock);
-
- /* Exclude any concurrent CPU-hotplug operations. */
- mutex_lock(&rsp->onoff_mutex);
-
- /*
- * Set the quiescent-state-needed bits in all the rcu_node
- * structures for all currently online CPUs in breadth-first order,
- * starting from the root rcu_node structure, relying on the layout
- * of the tree within the rsp->node[] array. Note that other CPUs
- * will access only the leaves of the hierarchy, thus seeing that no
- * grace period is in progress, at least until the corresponding
- * leaf node has been initialized. In addition, we have excluded
- * CPU-hotplug operations.
- *
- * The grace period cannot complete until the initialization
- * process finishes, because this kthread handles both.
- */
- rcu_for_each_node_breadth_first(rsp, rnp) {
- raw_spin_lock_irq(&rnp->lock);
- rdp = this_cpu_ptr(rsp->rda);
- rcu_preempt_check_blocked_tasks(rnp);
- rnp->qsmask = rnp->qsmaskinit;
- ACCESS_ONCE(rnp->gpnum) = rsp->gpnum;
- WARN_ON_ONCE(rnp->completed != rsp->completed);
- ACCESS_ONCE(rnp->completed) = rsp->completed;
- if (rnp == rdp->mynode)
- __note_gp_changes(rsp, rnp, rdp);
- rcu_preempt_boost_start_gp(rnp);
- trace_rcu_grace_period_init(rsp->name, rnp->gpnum,
- rnp->level, rnp->grplo,
- rnp->grphi, rnp->qsmask);
- raw_spin_unlock_irq(&rnp->lock);
-#ifdef CONFIG_PROVE_RCU_DELAY
- if ((prandom_u32() % (rcu_num_nodes + 1)) == 0 &&
- system_state == SYSTEM_RUNNING)
- udelay(200);
-#endif /* #ifdef CONFIG_PROVE_RCU_DELAY */
- cond_resched();
- }
-
- mutex_unlock(&rsp->onoff_mutex);
- return 1;
-}
-
-/*
- * Do one round of quiescent-state forcing.
- */
-static int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in)
-{
- int fqs_state = fqs_state_in;
- bool isidle = false;
- unsigned long maxj;
- struct rcu_node *rnp = rcu_get_root(rsp);
-
- rsp->n_force_qs++;
- if (fqs_state == RCU_SAVE_DYNTICK) {
- /* Collect dyntick-idle snapshots. */
- if (is_sysidle_rcu_state(rsp)) {
- isidle = 1;
- maxj = jiffies - ULONG_MAX / 4;
- }
- force_qs_rnp(rsp, dyntick_save_progress_counter,
- &isidle, &maxj);
- rcu_sysidle_report_gp(rsp, isidle, maxj);
- fqs_state = RCU_FORCE_QS;
- } else {
- /* Handle dyntick-idle and offline CPUs. */
- isidle = 0;
- force_qs_rnp(rsp, rcu_implicit_dynticks_qs, &isidle, &maxj);
- }
- /* Clear flag to prevent immediate re-entry. */
- if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
- raw_spin_lock_irq(&rnp->lock);
- rsp->gp_flags &= ~RCU_GP_FLAG_FQS;
- raw_spin_unlock_irq(&rnp->lock);
- }
- return fqs_state;
-}
-
-/*
- * Clean up after the old grace period.
- */
-static void rcu_gp_cleanup(struct rcu_state *rsp)
-{
- unsigned long gp_duration;
- int nocb = 0;
- struct rcu_data *rdp;
- struct rcu_node *rnp = rcu_get_root(rsp);
-
- raw_spin_lock_irq(&rnp->lock);
- gp_duration = jiffies - rsp->gp_start;
- if (gp_duration > rsp->gp_max)
- rsp->gp_max = gp_duration;
-
- /*
- * We know the grace period is complete, but to everyone else
- * it appears to still be ongoing. But it is also the case
- * that to everyone else it looks like there is nothing that
- * they can do to advance the grace period. It is therefore
- * safe for us to drop the lock in order to mark the grace
- * period as completed in all of the rcu_node structures.
- */
- raw_spin_unlock_irq(&rnp->lock);
-
- /*
- * Propagate new ->completed value to rcu_node structures so
- * that other CPUs don't have to wait until the start of the next
- * grace period to process their callbacks. This also avoids
- * some nasty RCU grace-period initialization races by forcing
- * the end of the current grace period to be completely recorded in
- * all of the rcu_node structures before the beginning of the next
- * grace period is recorded in any of the rcu_node structures.
- */
- rcu_for_each_node_breadth_first(rsp, rnp) {
- raw_spin_lock_irq(&rnp->lock);
- ACCESS_ONCE(rnp->completed) = rsp->gpnum;
- rdp = this_cpu_ptr(rsp->rda);
- if (rnp == rdp->mynode)
- __note_gp_changes(rsp, rnp, rdp);
- nocb += rcu_future_gp_cleanup(rsp, rnp);
- raw_spin_unlock_irq(&rnp->lock);
- cond_resched();
- }
- rnp = rcu_get_root(rsp);
- raw_spin_lock_irq(&rnp->lock);
- rcu_nocb_gp_set(rnp, nocb);
-
- rsp->completed = rsp->gpnum; /* Declare grace period done. */
- trace_rcu_grace_period(rsp->name, rsp->completed, TPS("end"));
- rsp->fqs_state = RCU_GP_IDLE;
- rdp = this_cpu_ptr(rsp->rda);
- rcu_advance_cbs(rsp, rnp, rdp); /* Reduce false positives below. */
- if (cpu_needs_another_gp(rsp, rdp)) {
- rsp->gp_flags = RCU_GP_FLAG_INIT;
- trace_rcu_grace_period(rsp->name,
- ACCESS_ONCE(rsp->gpnum),
- TPS("newreq"));
- }
- raw_spin_unlock_irq(&rnp->lock);
-}
-
-/*
- * Body of kthread that handles grace periods.
- */
-static int __noreturn rcu_gp_kthread(void *arg)
-{
- int fqs_state;
- int gf;
- unsigned long j;
- int ret;
- struct rcu_state *rsp = arg;
- struct rcu_node *rnp = rcu_get_root(rsp);
-
- for (;;) {
-
- /* Handle grace-period start. */
- for (;;) {
- trace_rcu_grace_period(rsp->name,
- ACCESS_ONCE(rsp->gpnum),
- TPS("reqwait"));
- wait_event_interruptible(rsp->gp_wq,
- ACCESS_ONCE(rsp->gp_flags) &
- RCU_GP_FLAG_INIT);
- if (rcu_gp_init(rsp))
- break;
- cond_resched();
- flush_signals(current);
- trace_rcu_grace_period(rsp->name,
- ACCESS_ONCE(rsp->gpnum),
- TPS("reqwaitsig"));
- }
-
- /* Handle quiescent-state forcing. */
- fqs_state = RCU_SAVE_DYNTICK;
- j = jiffies_till_first_fqs;
- if (j > HZ) {
- j = HZ;
- jiffies_till_first_fqs = HZ;
- }
- ret = 0;
- for (;;) {
- if (!ret)
- rsp->jiffies_force_qs = jiffies + j;
- trace_rcu_grace_period(rsp->name,
- ACCESS_ONCE(rsp->gpnum),
- TPS("fqswait"));
- ret = wait_event_interruptible_timeout(rsp->gp_wq,
- ((gf = ACCESS_ONCE(rsp->gp_flags)) &
- RCU_GP_FLAG_FQS) ||
- (!ACCESS_ONCE(rnp->qsmask) &&
- !rcu_preempt_blocked_readers_cgp(rnp)),
- j);
- /* If grace period done, leave loop. */
- if (!ACCESS_ONCE(rnp->qsmask) &&
- !rcu_preempt_blocked_readers_cgp(rnp))
- break;
- /* If time for quiescent-state forcing, do it. */
- if (ULONG_CMP_GE(jiffies, rsp->jiffies_force_qs) ||
- (gf & RCU_GP_FLAG_FQS)) {
- trace_rcu_grace_period(rsp->name,
- ACCESS_ONCE(rsp->gpnum),
- TPS("fqsstart"));
- fqs_state = rcu_gp_fqs(rsp, fqs_state);
- trace_rcu_grace_period(rsp->name,
- ACCESS_ONCE(rsp->gpnum),
- TPS("fqsend"));
- cond_resched();
- } else {
- /* Deal with stray signal. */
- cond_resched();
- flush_signals(current);
- trace_rcu_grace_period(rsp->name,
- ACCESS_ONCE(rsp->gpnum),
- TPS("fqswaitsig"));
- }
- j = jiffies_till_next_fqs;
- if (j > HZ) {
- j = HZ;
- jiffies_till_next_fqs = HZ;
- } else if (j < 1) {
- j = 1;
- jiffies_till_next_fqs = 1;
- }
- }
-
- /* Handle grace-period end. */
- rcu_gp_cleanup(rsp);
- }
-}
-
-static void rsp_wakeup(struct irq_work *work)
-{
- struct rcu_state *rsp = container_of(work, struct rcu_state, wakeup_work);
-
- /* Wake up rcu_gp_kthread() to start the grace period. */
- wake_up(&rsp->gp_wq);
-}
-
-/*
- * Start a new RCU grace period if warranted, re-initializing the hierarchy
- * in preparation for detecting the next grace period. The caller must hold
- * the root node's ->lock and hard irqs must be disabled.
- *
- * Note that it is legal for a dying CPU (which is marked as offline) to
- * invoke this function. This can happen when the dying CPU reports its
- * quiescent state.
- */
-static void
-rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
- struct rcu_data *rdp)
-{
- if (!rsp->gp_kthread || !cpu_needs_another_gp(rsp, rdp)) {
- /*
- * Either we have not yet spawned the grace-period
- * task, this CPU does not need another grace period,
- * or a grace period is already in progress.
- * Either way, don't start a new grace period.
- */
- return;
- }
- rsp->gp_flags = RCU_GP_FLAG_INIT;
- trace_rcu_grace_period(rsp->name, ACCESS_ONCE(rsp->gpnum),
- TPS("newreq"));
-
- /*
- * We can't do wakeups while holding the rnp->lock, as that
- * could cause possible deadlocks with the rq->lock. Defer
- * the wakeup to interrupt context. And don't bother waking
- * up the running kthread.
- */
- if (current != rsp->gp_kthread)
- irq_work_queue(&rsp->wakeup_work);
-}
-
-/*
- * Similar to rcu_start_gp_advanced(), but also advance the calling CPU's
- * callbacks. Note that rcu_start_gp_advanced() cannot do this because it
- * is invoked indirectly from rcu_advance_cbs(), which would result in
- * endless recursion -- or would do so if it wasn't for the self-deadlock
- * that is encountered beforehand.
- */
-static void
-rcu_start_gp(struct rcu_state *rsp)
-{
- struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
- struct rcu_node *rnp = rcu_get_root(rsp);
-
- /*
- * If there is no grace period in progress right now, any
- * callbacks we have up to this point will be satisfied by the
- * next grace period. Also, advancing the callbacks reduces the
- * probability of false positives from cpu_needs_another_gp()
- * resulting in pointless grace periods. So, advance callbacks
- * then start the grace period!
- */
- rcu_advance_cbs(rsp, rnp, rdp);
- rcu_start_gp_advanced(rsp, rnp, rdp);
-}
-
-/*
- * Report a full set of quiescent states to the specified rcu_state
- * data structure. This involves cleaning up after the prior grace
- * period and letting rcu_start_gp() start up the next grace period
- * if one is needed. Note that the caller must hold rnp->lock, which
- * is released before return.
- */
-static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
- __releases(rcu_get_root(rsp)->lock)
-{
- WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
- raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags);
- wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */
-}
-
-/*
- * Similar to rcu_report_qs_rdp(), for which it is a helper function.
- * Allows quiescent states for a group of CPUs to be reported at one go
- * to the specified rcu_node structure, though all the CPUs in the group
- * must be represented by the same rcu_node structure (which need not be
- * a leaf rcu_node structure, though it often will be). That structure's
- * lock must be held upon entry, and it is released before return.
- */
-static void
-rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
- struct rcu_node *rnp, unsigned long flags)
- __releases(rnp->lock)
-{
- struct rcu_node *rnp_c;
-
- /* Walk up the rcu_node hierarchy. */
- for (;;) {
- if (!(rnp->qsmask & mask)) {
-
- /* Our bit has already been cleared, so done. */
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- return;
- }
- rnp->qsmask &= ~mask;
- trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum,
- mask, rnp->qsmask, rnp->level,
- rnp->grplo, rnp->grphi,
- !!rnp->gp_tasks);
- if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
-
- /* Other bits still set at this level, so done. */
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- return;
- }
- mask = rnp->grpmask;
- if (rnp->parent == NULL) {
-
- /* No more levels. Exit loop holding root lock. */
-
- break;
- }
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- rnp_c = rnp;
- rnp = rnp->parent;
- raw_spin_lock_irqsave(&rnp->lock, flags);
- WARN_ON_ONCE(rnp_c->qsmask);
- }
-
- /*
- * Get here if we are the last CPU to pass through a quiescent
- * state for this grace period. Invoke rcu_report_qs_rsp()
- * to clean up and start the next grace period if one is needed.
- */
- rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */
-}
-
-/*
- * Record a quiescent state for the specified CPU to that CPU's rcu_data
- * structure. This must be either called from the specified CPU, or
- * called when the specified CPU is known to be offline (and when it is
- * also known that no other CPU is concurrently trying to help the offline
- * CPU). The lastcomp argument is used to make sure we are still in the
- * grace period of interest. We don't want to end the current grace period
- * based on quiescent states detected in an earlier grace period!
- */
-static void
-rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
-{
- unsigned long flags;
- unsigned long mask;
- struct rcu_node *rnp;
-
- rnp = rdp->mynode;
- raw_spin_lock_irqsave(&rnp->lock, flags);
- if (rdp->passed_quiesce == 0 || rdp->gpnum != rnp->gpnum ||
- rnp->completed == rnp->gpnum) {
-
- /*
- * The grace period in which this quiescent state was
- * recorded has ended, so don't report it upwards.
- * We will instead need a new quiescent state that lies
- * within the current grace period.
- */
- rdp->passed_quiesce = 0; /* need qs for new gp. */
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- return;
- }
- mask = rdp->grpmask;
- if ((rnp->qsmask & mask) == 0) {
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- } else {
- rdp->qs_pending = 0;
-
- /*
- * This GP can't end until cpu checks in, so all of our
- * callbacks can be processed during the next GP.
- */
- rcu_accelerate_cbs(rsp, rnp, rdp);
-
- rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */
- }
-}
-
-/*
- * Check to see if there is a new grace period of which this CPU
- * is not yet aware, and if so, set up local rcu_data state for it.
- * Otherwise, see if this CPU has just passed through its first
- * quiescent state for this grace period, and record that fact if so.
- */
-static void
-rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
-{
- /* Check for grace-period ends and beginnings. */
- note_gp_changes(rsp, rdp);
-
- /*
- * Does this CPU still need to do its part for current grace period?
- * If no, return and let the other CPUs do their part as well.
- */
- if (!rdp->qs_pending)
- return;
-
- /*
- * Was there a quiescent state since the beginning of the grace
- * period? If no, then exit and wait for the next call.
- */
- if (!rdp->passed_quiesce)
- return;
-
- /*
- * Tell RCU we are done (but rcu_report_qs_rdp() will be the
- * judge of that).
- */
- rcu_report_qs_rdp(rdp->cpu, rsp, rdp);
-}
-
-#ifdef CONFIG_HOTPLUG_CPU
-
-/*
- * Send the specified CPU's RCU callbacks to the orphanage. The
- * specified CPU must be offline, and the caller must hold the
- * ->orphan_lock.
- */
-static void
-rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
- struct rcu_node *rnp, struct rcu_data *rdp)
-{
- /* No-CBs CPUs do not have orphanable callbacks. */
- if (rcu_is_nocb_cpu(rdp->cpu))
- return;
-
- /*
- * Orphan the callbacks. First adjust the counts. This is safe
- * because _rcu_barrier() excludes CPU-hotplug operations, so it
- * cannot be running now. Thus no memory barrier is required.
- */
- if (rdp->nxtlist != NULL) {
- rsp->qlen_lazy += rdp->qlen_lazy;
- rsp->qlen += rdp->qlen;
- rdp->n_cbs_orphaned += rdp->qlen;
- rdp->qlen_lazy = 0;
- ACCESS_ONCE(rdp->qlen) = 0;
- }
-
- /*
- * Next, move those callbacks still needing a grace period to
- * the orphanage, where some other CPU will pick them up.
- * Some of the callbacks might have gone partway through a grace
- * period, but that is too bad. They get to start over because we
- * cannot assume that grace periods are synchronized across CPUs.
- * We don't bother updating the ->nxttail[] array yet, instead
- * we just reset the whole thing later on.
- */
- if (*rdp->nxttail[RCU_DONE_TAIL] != NULL) {
- *rsp->orphan_nxttail = *rdp->nxttail[RCU_DONE_TAIL];
- rsp->orphan_nxttail = rdp->nxttail[RCU_NEXT_TAIL];
- *rdp->nxttail[RCU_DONE_TAIL] = NULL;
- }
-
- /*
- * Then move the ready-to-invoke callbacks to the orphanage,
- * where some other CPU will pick them up. These will not be
- * required to pass though another grace period: They are done.
- */
- if (rdp->nxtlist != NULL) {
- *rsp->orphan_donetail = rdp->nxtlist;
- rsp->orphan_donetail = rdp->nxttail[RCU_DONE_TAIL];
- }
-
- /* Finally, initialize the rcu_data structure's list to empty. */
- init_callback_list(rdp);
-}
-
-/*
- * Adopt the RCU callbacks from the specified rcu_state structure's
- * orphanage. The caller must hold the ->orphan_lock.
- */
-static void rcu_adopt_orphan_cbs(struct rcu_state *rsp)
-{
- int i;
- struct rcu_data *rdp = __this_cpu_ptr(rsp->rda);
-
- /* No-CBs CPUs are handled specially. */
- if (rcu_nocb_adopt_orphan_cbs(rsp, rdp))
- return;
-
- /* Do the accounting first. */
- rdp->qlen_lazy += rsp->qlen_lazy;
- rdp->qlen += rsp->qlen;
- rdp->n_cbs_adopted += rsp->qlen;
- if (rsp->qlen_lazy != rsp->qlen)
- rcu_idle_count_callbacks_posted();
- rsp->qlen_lazy = 0;
- rsp->qlen = 0;
-
- /*
- * We do not need a memory barrier here because the only way we
- * can get here if there is an rcu_barrier() in flight is if
- * we are the task doing the rcu_barrier().
- */
-
- /* First adopt the ready-to-invoke callbacks. */
- if (rsp->orphan_donelist != NULL) {
- *rsp->orphan_donetail = *rdp->nxttail[RCU_DONE_TAIL];
- *rdp->nxttail[RCU_DONE_TAIL] = rsp->orphan_donelist;
- for (i = RCU_NEXT_SIZE - 1; i >= RCU_DONE_TAIL; i--)
- if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL])
- rdp->nxttail[i] = rsp->orphan_donetail;
- rsp->orphan_donelist = NULL;
- rsp->orphan_donetail = &rsp->orphan_donelist;
- }
-
- /* And then adopt the callbacks that still need a grace period. */
- if (rsp->orphan_nxtlist != NULL) {
- *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxtlist;
- rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxttail;
- rsp->orphan_nxtlist = NULL;
- rsp->orphan_nxttail = &rsp->orphan_nxtlist;
- }
-}
-
-/*
- * Trace the fact that this CPU is going offline.
- */
-static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
-{
- RCU_TRACE(unsigned long mask);
- RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda));
- RCU_TRACE(struct rcu_node *rnp = rdp->mynode);
-
- RCU_TRACE(mask = rdp->grpmask);
- trace_rcu_grace_period(rsp->name,
- rnp->gpnum + 1 - !!(rnp->qsmask & mask),
- TPS("cpuofl"));
-}
-
-/*
- * The CPU has been completely removed, and some other CPU is reporting
- * this fact from process context. Do the remainder of the cleanup,
- * including orphaning the outgoing CPU's RCU callbacks, and also
- * adopting them. There can only be one CPU hotplug operation at a time,
- * so no other CPU can be attempting to update rcu_cpu_kthread_task.
- */
-static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
-{
- unsigned long flags;
- unsigned long mask;
- int need_report = 0;
- struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
- struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */
-
- /* Adjust any no-longer-needed kthreads. */
- rcu_boost_kthread_setaffinity(rnp, -1);
-
- /* Remove the dead CPU from the bitmasks in the rcu_node hierarchy. */
-
- /* Exclude any attempts to start a new grace period. */
- mutex_lock(&rsp->onoff_mutex);
- raw_spin_lock_irqsave(&rsp->orphan_lock, flags);
-
- /* Orphan the dead CPU's callbacks, and adopt them if appropriate. */
- rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp);
- rcu_adopt_orphan_cbs(rsp);
-
- /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
- mask = rdp->grpmask; /* rnp->grplo is constant. */
- do {
- raw_spin_lock(&rnp->lock); /* irqs already disabled. */
- rnp->qsmaskinit &= ~mask;
- if (rnp->qsmaskinit != 0) {
- if (rnp != rdp->mynode)
- raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
- break;
- }
- if (rnp == rdp->mynode)
- need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp);
- else
- raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
- mask = rnp->grpmask;
- rnp = rnp->parent;
- } while (rnp != NULL);
-
- /*
- * We still hold the leaf rcu_node structure lock here, and
- * irqs are still disabled. The reason for this subterfuge is
- * because invoking rcu_report_unblock_qs_rnp() with ->orphan_lock
- * held leads to deadlock.
- */
- raw_spin_unlock(&rsp->orphan_lock); /* irqs remain disabled. */
- rnp = rdp->mynode;
- if (need_report & RCU_OFL_TASKS_NORM_GP)
- rcu_report_unblock_qs_rnp(rnp, flags);
- else
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- if (need_report & RCU_OFL_TASKS_EXP_GP)
- rcu_report_exp_rnp(rsp, rnp, true);
- WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL,
- "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n",
- cpu, rdp->qlen, rdp->nxtlist);
- init_callback_list(rdp);
- /* Disallow further callbacks on this CPU. */
- rdp->nxttail[RCU_NEXT_TAIL] = NULL;
- mutex_unlock(&rsp->onoff_mutex);
-}
-
-#else /* #ifdef CONFIG_HOTPLUG_CPU */
-
-static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
-{
-}
-
-static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
-{
-}
-
-#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
-
-/*
- * Invoke any RCU callbacks that have made it to the end of their grace
- * period. Thottle as specified by rdp->blimit.
- */
-static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
-{
- unsigned long flags;
- struct rcu_head *next, *list, **tail;
- long bl, count, count_lazy;
- int i;
-
- /* If no callbacks are ready, just return. */
- if (!cpu_has_callbacks_ready_to_invoke(rdp)) {
- trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0);
- trace_rcu_batch_end(rsp->name, 0, !!ACCESS_ONCE(rdp->nxtlist),
- need_resched(), is_idle_task(current),
- rcu_is_callbacks_kthread());
- return;
- }
-
- /*
- * Extract the list of ready callbacks, disabling to prevent
- * races with call_rcu() from interrupt handlers.
- */
- local_irq_save(flags);
- WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
- bl = rdp->blimit;
- trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl);
- list = rdp->nxtlist;
- rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL];
- *rdp->nxttail[RCU_DONE_TAIL] = NULL;
- tail = rdp->nxttail[RCU_DONE_TAIL];
- for (i = RCU_NEXT_SIZE - 1; i >= 0; i--)
- if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL])
- rdp->nxttail[i] = &rdp->nxtlist;
- local_irq_restore(flags);
-
- /* Invoke callbacks. */
- count = count_lazy = 0;
- while (list) {
- next = list->next;
- prefetch(next);
- debug_rcu_head_unqueue(list);
- if (__rcu_reclaim(rsp->name, list))
- count_lazy++;
- list = next;
- /* Stop only if limit reached and CPU has something to do. */
- if (++count >= bl &&
- (need_resched() ||
- (!is_idle_task(current) && !rcu_is_callbacks_kthread())))
- break;
- }
-
- local_irq_save(flags);
- trace_rcu_batch_end(rsp->name, count, !!list, need_resched(),
- is_idle_task(current),
- rcu_is_callbacks_kthread());
-
- /* Update count, and requeue any remaining callbacks. */
- if (list != NULL) {
- *tail = rdp->nxtlist;
- rdp->nxtlist = list;
- for (i = 0; i < RCU_NEXT_SIZE; i++)
- if (&rdp->nxtlist == rdp->nxttail[i])
- rdp->nxttail[i] = tail;
- else
- break;
- }
- smp_mb(); /* List handling before counting for rcu_barrier(). */
- rdp->qlen_lazy -= count_lazy;
- ACCESS_ONCE(rdp->qlen) -= count;
- rdp->n_cbs_invoked += count;
-
- /* Reinstate batch limit if we have worked down the excess. */
- if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark)
- rdp->blimit = blimit;
-
- /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */
- if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) {
- rdp->qlen_last_fqs_check = 0;
- rdp->n_force_qs_snap = rsp->n_force_qs;
- } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark)
- rdp->qlen_last_fqs_check = rdp->qlen;
- WARN_ON_ONCE((rdp->nxtlist == NULL) != (rdp->qlen == 0));
-
- local_irq_restore(flags);
-
- /* Re-invoke RCU core processing if there are callbacks remaining. */
- if (cpu_has_callbacks_ready_to_invoke(rdp))
- invoke_rcu_core();
-}
-
-/*
- * Check to see if this CPU is in a non-context-switch quiescent state
- * (user mode or idle loop for rcu, non-softirq execution for rcu_bh).
- * Also schedule RCU core processing.
- *
- * This function must be called from hardirq context. It is normally
- * invoked from the scheduling-clock interrupt. If rcu_pending returns
- * false, there is no point in invoking rcu_check_callbacks().
- */
-void rcu_check_callbacks(int cpu, int user)
-{
- trace_rcu_utilization(TPS("Start scheduler-tick"));
- increment_cpu_stall_ticks();
- if (user || rcu_is_cpu_rrupt_from_idle()) {
-
- /*
- * Get here if this CPU took its interrupt from user
- * mode or from the idle loop, and if this is not a
- * nested interrupt. In this case, the CPU is in
- * a quiescent state, so note it.
- *
- * No memory barrier is required here because both
- * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local
- * variables that other CPUs neither access nor modify,
- * at least not while the corresponding CPU is online.
- */
-
- rcu_sched_qs(cpu);
- rcu_bh_qs(cpu);
-
- } else if (!in_softirq()) {
-
- /*
- * Get here if this CPU did not take its interrupt from
- * softirq, in other words, if it is not interrupting
- * a rcu_bh read-side critical section. This is an _bh
- * critical section, so note it.
- */
-
- rcu_bh_qs(cpu);
- }
- rcu_preempt_check_callbacks(cpu);
- if (rcu_pending(cpu))
- invoke_rcu_core();
- trace_rcu_utilization(TPS("End scheduler-tick"));
-}
-
-/*
- * Scan the leaf rcu_node structures, processing dyntick state for any that
- * have not yet encountered a quiescent state, using the function specified.
- * Also initiate boosting for any threads blocked on the root rcu_node.
- *
- * The caller must have suppressed start of new grace periods.
- */
-static void force_qs_rnp(struct rcu_state *rsp,
- int (*f)(struct rcu_data *rsp, bool *isidle,
- unsigned long *maxj),
- bool *isidle, unsigned long *maxj)
-{
- unsigned long bit;
- int cpu;
- unsigned long flags;
- unsigned long mask;
- struct rcu_node *rnp;
-
- rcu_for_each_leaf_node(rsp, rnp) {
- cond_resched();
- mask = 0;
- raw_spin_lock_irqsave(&rnp->lock, flags);
- if (!rcu_gp_in_progress(rsp)) {
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- return;
- }
- if (rnp->qsmask == 0) {
- rcu_initiate_boost(rnp, flags); /* releases rnp->lock */
- continue;
- }
- cpu = rnp->grplo;
- bit = 1;
- for (; cpu <= rnp->grphi; cpu++, bit <<= 1) {
- if ((rnp->qsmask & bit) != 0) {
- if ((rnp->qsmaskinit & bit) != 0)
- *isidle = 0;
- if (f(per_cpu_ptr(rsp->rda, cpu), isidle, maxj))
- mask |= bit;
- }
- }
- if (mask != 0) {
-
- /* rcu_report_qs_rnp() releases rnp->lock. */
- rcu_report_qs_rnp(mask, rsp, rnp, flags);
- continue;
- }
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- }
- rnp = rcu_get_root(rsp);
- if (rnp->qsmask == 0) {
- raw_spin_lock_irqsave(&rnp->lock, flags);
- rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
- }
-}
-
-/*
- * Force quiescent states on reluctant CPUs, and also detect which
- * CPUs are in dyntick-idle mode.
- */
-static void force_quiescent_state(struct rcu_state *rsp)
-{
- unsigned long flags;
- bool ret;
- struct rcu_node *rnp;
- struct rcu_node *rnp_old = NULL;
-
- /* Funnel through hierarchy to reduce memory contention. */
- rnp = per_cpu_ptr(rsp->rda, raw_smp_processor_id())->mynode;
- for (; rnp != NULL; rnp = rnp->parent) {
- ret = (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) ||
- !raw_spin_trylock(&rnp->fqslock);
- if (rnp_old != NULL)
- raw_spin_unlock(&rnp_old->fqslock);
- if (ret) {
- rsp->n_force_qs_lh++;
- return;
- }
- rnp_old = rnp;
- }
- /* rnp_old == rcu_get_root(rsp), rnp == NULL. */
-
- /* Reached the root of the rcu_node tree, acquire lock. */
- raw_spin_lock_irqsave(&rnp_old->lock, flags);
- raw_spin_unlock(&rnp_old->fqslock);
- if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
- rsp->n_force_qs_lh++;
- raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
- return; /* Someone beat us to it. */
- }
- rsp->gp_flags |= RCU_GP_FLAG_FQS;
- raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
- wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */
-}
-
-/*
- * This does the RCU core processing work for the specified rcu_state
- * and rcu_data structures. This may be called only from the CPU to
- * whom the rdp belongs.
- */
-static void
-__rcu_process_callbacks(struct rcu_state *rsp)
-{
- unsigned long flags;
- struct rcu_data *rdp = __this_cpu_ptr(rsp->rda);
-
- WARN_ON_ONCE(rdp->beenonline == 0);
-
- /* Update RCU state based on any recent quiescent states. */
- rcu_check_quiescent_state(rsp, rdp);
-
- /* Does this CPU require a not-yet-started grace period? */
- local_irq_save(flags);
- if (cpu_needs_another_gp(rsp, rdp)) {
- raw_spin_lock(&rcu_get_root(rsp)->lock); /* irqs disabled. */
- rcu_start_gp(rsp);
- raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags);
- } else {
- local_irq_restore(flags);
- }
-
- /* If there are callbacks ready, invoke them. */
- if (cpu_has_callbacks_ready_to_invoke(rdp))
- invoke_rcu_callbacks(rsp, rdp);
-}
-
-/*
- * Do RCU core processing for the current CPU.
- */
-static void rcu_process_callbacks(struct softirq_action *unused)
-{
- struct rcu_state *rsp;
-
- if (cpu_is_offline(smp_processor_id()))
- return;
- trace_rcu_utilization(TPS("Start RCU core"));
- for_each_rcu_flavor(rsp)
- __rcu_process_callbacks(rsp);
- trace_rcu_utilization(TPS("End RCU core"));
-}
-
-/*
- * Schedule RCU callback invocation. If the specified type of RCU
- * does not support RCU priority boosting, just do a direct call,
- * otherwise wake up the per-CPU kernel kthread. Note that because we
- * are running on the current CPU with interrupts disabled, the
- * rcu_cpu_kthread_task cannot disappear out from under us.
- */
-static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
-{
- if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active)))
- return;
- if (likely(!rsp->boost)) {
- rcu_do_batch(rsp, rdp);
- return;
- }
- invoke_rcu_callbacks_kthread();
-}
-
-static void invoke_rcu_core(void)
-{
- if (cpu_online(smp_processor_id()))
- raise_softirq(RCU_SOFTIRQ);
-}
-
-/*
- * Handle any core-RCU processing required by a call_rcu() invocation.
- */
-static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp,
- struct rcu_head *head, unsigned long flags)
-{
- /*
- * If called from an extended quiescent state, invoke the RCU
- * core in order to force a re-evaluation of RCU's idleness.
- */
- if (!rcu_is_watching() && cpu_online(smp_processor_id()))
- invoke_rcu_core();
-
- /* If interrupts were disabled or CPU offline, don't invoke RCU core. */
- if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id()))
- return;
-
- /*
- * Force the grace period if too many callbacks or too long waiting.
- * Enforce hysteresis, and don't invoke force_quiescent_state()
- * if some other CPU has recently done so. Also, don't bother
- * invoking force_quiescent_state() if the newly enqueued callback
- * is the only one waiting for a grace period to complete.
- */
- if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) {
-
- /* Are we ignoring a completed grace period? */
- note_gp_changes(rsp, rdp);
-
- /* Start a new grace period if one not already started. */
- if (!rcu_gp_in_progress(rsp)) {
- struct rcu_node *rnp_root = rcu_get_root(rsp);
-
- raw_spin_lock(&rnp_root->lock);
- rcu_start_gp(rsp);
- raw_spin_unlock(&rnp_root->lock);
- } else {
- /* Give the grace period a kick. */
- rdp->blimit = LONG_MAX;
- if (rsp->n_force_qs == rdp->n_force_qs_snap &&
- *rdp->nxttail[RCU_DONE_TAIL] != head)
- force_quiescent_state(rsp);
- rdp->n_force_qs_snap = rsp->n_force_qs;
- rdp->qlen_last_fqs_check = rdp->qlen;
- }
- }
-}
-
-/*
- * RCU callback function to leak a callback.
- */
-static void rcu_leak_callback(struct rcu_head *rhp)
-{
-}
-
-/*
- * Helper function for call_rcu() and friends. The cpu argument will
- * normally be -1, indicating "currently running CPU". It may specify
- * a CPU only if that CPU is a no-CBs CPU. Currently, only _rcu_barrier()
- * is expected to specify a CPU.
- */
-static void
-__call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
- struct rcu_state *rsp, int cpu, bool lazy)
-{
- unsigned long flags;
- struct rcu_data *rdp;
-
- WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */
- if (debug_rcu_head_queue(head)) {
- /* Probable double call_rcu(), so leak the callback. */
- ACCESS_ONCE(head->func) = rcu_leak_callback;
- WARN_ONCE(1, "__call_rcu(): Leaked duplicate callback\n");
- return;
- }
- head->func = func;
- head->next = NULL;
-
- /*
- * Opportunistically note grace-period endings and beginnings.
- * Note that we might see a beginning right after we see an
- * end, but never vice versa, since this CPU has to pass through
- * a quiescent state betweentimes.
- */
- local_irq_save(flags);
- rdp = this_cpu_ptr(rsp->rda);
-
- /* Add the callback to our list. */
- if (unlikely(rdp->nxttail[RCU_NEXT_TAIL] == NULL) || cpu != -1) {
- int offline;
-
- if (cpu != -1)
- rdp = per_cpu_ptr(rsp->rda, cpu);
- offline = !__call_rcu_nocb(rdp, head, lazy);
- WARN_ON_ONCE(offline);
- /* _call_rcu() is illegal on offline CPU; leak the callback. */
- local_irq_restore(flags);
- return;
- }
- ACCESS_ONCE(rdp->qlen)++;
- if (lazy)
- rdp->qlen_lazy++;
- else
- rcu_idle_count_callbacks_posted();
- smp_mb(); /* Count before adding callback for rcu_barrier(). */
- *rdp->nxttail[RCU_NEXT_TAIL] = head;
- rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
-
- if (__is_kfree_rcu_offset((unsigned long)func))
- trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func,
- rdp->qlen_lazy, rdp->qlen);
- else
- trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen);
-
- /* Go handle any RCU core processing required. */
- __call_rcu_core(rsp, rdp, head, flags);
- local_irq_restore(flags);
-}
-
-/*
- * Queue an RCU-sched callback for invocation after a grace period.
- */
-void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
-{
- __call_rcu(head, func, &rcu_sched_state, -1, 0);
-}
-EXPORT_SYMBOL_GPL(call_rcu_sched);
-
-/*
- * Queue an RCU callback for invocation after a quicker grace period.
- */
-void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
-{
- __call_rcu(head, func, &rcu_bh_state, -1, 0);
-}
-EXPORT_SYMBOL_GPL(call_rcu_bh);
-
-/*
- * Because a context switch is a grace period for RCU-sched and RCU-bh,
- * any blocking grace-period wait automatically implies a grace period
- * if there is only one CPU online at any point time during execution
- * of either synchronize_sched() or synchronize_rcu_bh(). It is OK to
- * occasionally incorrectly indicate that there are multiple CPUs online
- * when there was in fact only one the whole time, as this just adds
- * some overhead: RCU still operates correctly.
- */
-static inline int rcu_blocking_is_gp(void)
-{
- int ret;
-
- might_sleep(); /* Check for RCU read-side critical section. */
- preempt_disable();
- ret = num_online_cpus() <= 1;
- preempt_enable();
- return ret;
-}
-
-/**
- * synchronize_sched - wait until an rcu-sched grace period has elapsed.
- *
- * Control will return to the caller some time after a full rcu-sched
- * grace period has elapsed, in other words after all currently executing
- * rcu-sched read-side critical sections have completed. These read-side
- * critical sections are delimited by rcu_read_lock_sched() and
- * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(),
- * local_irq_disable(), and so on may be used in place of
- * rcu_read_lock_sched().
- *
- * This means that all preempt_disable code sequences, including NMI and
- * non-threaded hardware-interrupt handlers, in progress on entry will
- * have completed before this primitive returns. However, this does not
- * guarantee that softirq handlers will have completed, since in some
- * kernels, these handlers can run in process context, and can block.
- *
- * Note that this guarantee implies further memory-ordering guarantees.
- * On systems with more than one CPU, when synchronize_sched() returns,
- * each CPU is guaranteed to have executed a full memory barrier since the
- * end of its last RCU-sched read-side critical section whose beginning
- * preceded the call to synchronize_sched(). In addition, each CPU having
- * an RCU read-side critical section that extends beyond the return from
- * synchronize_sched() is guaranteed to have executed a full memory barrier
- * after the beginning of synchronize_sched() and before the beginning of
- * that RCU read-side critical section. Note that these guarantees include
- * CPUs that are offline, idle, or executing in user mode, as well as CPUs
- * that are executing in the kernel.
- *
- * Furthermore, if CPU A invoked synchronize_sched(), which returned
- * to its caller on CPU B, then both CPU A and CPU B are guaranteed
- * to have executed a full memory barrier during the execution of
- * synchronize_sched() -- even if CPU A and CPU B are the same CPU (but
- * again only if the system has more than one CPU).
- *
- * This primitive provides the guarantees made by the (now removed)
- * synchronize_kernel() API. In contrast, synchronize_rcu() only
- * guarantees that rcu_read_lock() sections will have completed.
- * In "classic RCU", these two guarantees happen to be one and
- * the same, but can differ in realtime RCU implementations.
- */
-void synchronize_sched(void)
-{
- rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
- !lock_is_held(&rcu_lock_map) &&
- !lock_is_held(&rcu_sched_lock_map),
- "Illegal synchronize_sched() in RCU-sched read-side critical section");
- if (rcu_blocking_is_gp())
- return;
- if (rcu_expedited)
- synchronize_sched_expedited();
- else
- wait_rcu_gp(call_rcu_sched);
-}
-EXPORT_SYMBOL_GPL(synchronize_sched);
-
-/**
- * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
- *
- * Control will return to the caller some time after a full rcu_bh grace
- * period has elapsed, in other words after all currently executing rcu_bh
- * read-side critical sections have completed. RCU read-side critical
- * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(),
- * and may be nested.
- *
- * See the description of synchronize_sched() for more detailed information
- * on memory ordering guarantees.
- */
-void synchronize_rcu_bh(void)
-{
- rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
- !lock_is_held(&rcu_lock_map) &&
- !lock_is_held(&rcu_sched_lock_map),
- "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section");
- if (rcu_blocking_is_gp())
- return;
- if (rcu_expedited)
- synchronize_rcu_bh_expedited();
- else
- wait_rcu_gp(call_rcu_bh);
-}
-EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
-
-static int synchronize_sched_expedited_cpu_stop(void *data)
-{
- /*
- * There must be a full memory barrier on each affected CPU
- * between the time that try_stop_cpus() is called and the
- * time that it returns.
- *
- * In the current initial implementation of cpu_stop, the
- * above condition is already met when the control reaches
- * this point and the following smp_mb() is not strictly
- * necessary. Do smp_mb() anyway for documentation and
- * robustness against future implementation changes.
- */
- smp_mb(); /* See above comment block. */
- return 0;
-}
-
-/**
- * synchronize_sched_expedited - Brute-force RCU-sched grace period
- *
- * Wait for an RCU-sched grace period to elapse, but use a "big hammer"
- * approach to force the grace period to end quickly. This consumes
- * significant time on all CPUs and is unfriendly to real-time workloads,
- * so is thus not recommended for any sort of common-case code. In fact,
- * if you are using synchronize_sched_expedited() in a loop, please
- * restructure your code to batch your updates, and then use a single
- * synchronize_sched() instead.
- *
- * Note that it is illegal to call this function while holding any lock
- * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal
- * to call this function from a CPU-hotplug notifier. Failing to observe
- * these restriction will result in deadlock.
- *
- * This implementation can be thought of as an application of ticket
- * locking to RCU, with sync_sched_expedited_started and
- * sync_sched_expedited_done taking on the roles of the halves
- * of the ticket-lock word. Each task atomically increments
- * sync_sched_expedited_started upon entry, snapshotting the old value,
- * then attempts to stop all the CPUs. If this succeeds, then each
- * CPU will have executed a context switch, resulting in an RCU-sched
- * grace period. We are then done, so we use atomic_cmpxchg() to
- * update sync_sched_expedited_done to match our snapshot -- but
- * only if someone else has not already advanced past our snapshot.
- *
- * On the other hand, if try_stop_cpus() fails, we check the value
- * of sync_sched_expedited_done. If it has advanced past our
- * initial snapshot, then someone else must have forced a grace period
- * some time after we took our snapshot. In this case, our work is
- * done for us, and we can simply return. Otherwise, we try again,
- * but keep our initial snapshot for purposes of checking for someone
- * doing our work for us.
- *
- * If we fail too many times in a row, we fall back to synchronize_sched().
- */
-void synchronize_sched_expedited(void)
-{
- long firstsnap, s, snap;
- int trycount = 0;
- struct rcu_state *rsp = &rcu_sched_state;
-
- /*
- * If we are in danger of counter wrap, just do synchronize_sched().
- * By allowing sync_sched_expedited_started to advance no more than
- * ULONG_MAX/8 ahead of sync_sched_expedited_done, we are ensuring
- * that more than 3.5 billion CPUs would be required to force a
- * counter wrap on a 32-bit system. Quite a few more CPUs would of
- * course be required on a 64-bit system.
- */
- if (ULONG_CMP_GE((ulong)atomic_long_read(&rsp->expedited_start),
- (ulong)atomic_long_read(&rsp->expedited_done) +
- ULONG_MAX / 8)) {
- synchronize_sched();
- atomic_long_inc(&rsp->expedited_wrap);
- return;
- }
-
- /*
- * Take a ticket. Note that atomic_inc_return() implies a
- * full memory barrier.
- */
- snap = atomic_long_inc_return(&rsp->expedited_start);
- firstsnap = snap;
- get_online_cpus();
- WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
-
- /*
- * Each pass through the following loop attempts to force a
- * context switch on each CPU.
- */
- while (try_stop_cpus(cpu_online_mask,
- synchronize_sched_expedited_cpu_stop,
- NULL) == -EAGAIN) {
- put_online_cpus();
- atomic_long_inc(&rsp->expedited_tryfail);
-
- /* Check to see if someone else did our work for us. */
- s = atomic_long_read(&rsp->expedited_done);
- if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) {
- /* ensure test happens before caller kfree */
- smp_mb__before_atomic_inc(); /* ^^^ */
- atomic_long_inc(&rsp->expedited_workdone1);
- return;
- }
-
- /* No joy, try again later. Or just synchronize_sched(). */
- if (trycount++ < 10) {
- udelay(trycount * num_online_cpus());
- } else {
- wait_rcu_gp(call_rcu_sched);
- atomic_long_inc(&rsp->expedited_normal);
- return;
- }
-
- /* Recheck to see if someone else did our work for us. */
- s = atomic_long_read(&rsp->expedited_done);
- if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) {
- /* ensure test happens before caller kfree */
- smp_mb__before_atomic_inc(); /* ^^^ */
- atomic_long_inc(&rsp->expedited_workdone2);
- return;
- }
-
- /*
- * Refetching sync_sched_expedited_started allows later
- * callers to piggyback on our grace period. We retry
- * after they started, so our grace period works for them,
- * and they started after our first try, so their grace
- * period works for us.
- */
- get_online_cpus();
- snap = atomic_long_read(&rsp->expedited_start);
- smp_mb(); /* ensure read is before try_stop_cpus(). */
- }
- atomic_long_inc(&rsp->expedited_stoppedcpus);
-
- /*
- * Everyone up to our most recent fetch is covered by our grace
- * period. Update the counter, but only if our work is still
- * relevant -- which it won't be if someone who started later
- * than we did already did their update.
- */
- do {
- atomic_long_inc(&rsp->expedited_done_tries);
- s = atomic_long_read(&rsp->expedited_done);
- if (ULONG_CMP_GE((ulong)s, (ulong)snap)) {
- /* ensure test happens before caller kfree */
- smp_mb__before_atomic_inc(); /* ^^^ */
- atomic_long_inc(&rsp->expedited_done_lost);
- break;
- }
- } while (atomic_long_cmpxchg(&rsp->expedited_done, s, snap) != s);
- atomic_long_inc(&rsp->expedited_done_exit);
-
- put_online_cpus();
-}
-EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
-
-/*
- * Check to see if there is any immediate RCU-related work to be done
- * by the current CPU, for the specified type of RCU, returning 1 if so.
- * The checks are in order of increasing expense: checks that can be
- * carried out against CPU-local state are performed first. However,
- * we must check for CPU stalls first, else we might not get a chance.
- */
-static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
-{
- struct rcu_node *rnp = rdp->mynode;
-
- rdp->n_rcu_pending++;
-
- /* Check for CPU stalls, if enabled. */
- check_cpu_stall(rsp, rdp);
-
- /* Is the RCU core waiting for a quiescent state from this CPU? */
- if (rcu_scheduler_fully_active &&
- rdp->qs_pending && !rdp->passed_quiesce) {
- rdp->n_rp_qs_pending++;
- } else if (rdp->qs_pending && rdp->passed_quiesce) {
- rdp->n_rp_report_qs++;
- return 1;
- }
-
- /* Does this CPU have callbacks ready to invoke? */
- if (cpu_has_callbacks_ready_to_invoke(rdp)) {
- rdp->n_rp_cb_ready++;
- return 1;
- }
-
- /* Has RCU gone idle with this CPU needing another grace period? */
- if (cpu_needs_another_gp(rsp, rdp)) {
- rdp->n_rp_cpu_needs_gp++;
- return 1;
- }
-
- /* Has another RCU grace period completed? */
- if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */
- rdp->n_rp_gp_completed++;
- return 1;
- }
-
- /* Has a new RCU grace period started? */
- if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */
- rdp->n_rp_gp_started++;
- return 1;
- }
-
- /* nothing to do */
- rdp->n_rp_need_nothing++;
- return 0;
-}
-
-/*
- * Check to see if there is any immediate RCU-related work to be done
- * by the current CPU, returning 1 if so. This function is part of the
- * RCU implementation; it is -not- an exported member of the RCU API.
- */
-static int rcu_pending(int cpu)
-{
- struct rcu_state *rsp;
-
- for_each_rcu_flavor(rsp)
- if (__rcu_pending(rsp, per_cpu_ptr(rsp->rda, cpu)))
- return 1;
- return 0;
-}
-
-/*
- * Return true if the specified CPU has any callback. If all_lazy is
- * non-NULL, store an indication of whether all callbacks are lazy.
- * (If there are no callbacks, all of them are deemed to be lazy.)
- */
-static int rcu_cpu_has_callbacks(int cpu, bool *all_lazy)
-{
- bool al = true;
- bool hc = false;
- struct rcu_data *rdp;
- struct rcu_state *rsp;
-
- for_each_rcu_flavor(rsp) {
- rdp = per_cpu_ptr(rsp->rda, cpu);
- if (!rdp->nxtlist)
- continue;
- hc = true;
- if (rdp->qlen != rdp->qlen_lazy || !all_lazy) {
- al = false;
- break;
- }
- }
- if (all_lazy)
- *all_lazy = al;
- return hc;
-}
-
-/*
- * Helper function for _rcu_barrier() tracing. If tracing is disabled,
- * the compiler is expected to optimize this away.
- */
-static void _rcu_barrier_trace(struct rcu_state *rsp, const char *s,
- int cpu, unsigned long done)
-{
- trace_rcu_barrier(rsp->name, s, cpu,
- atomic_read(&rsp->barrier_cpu_count), done);
-}
-
-/*
- * RCU callback function for _rcu_barrier(). If we are last, wake
- * up the task executing _rcu_barrier().
- */
-static void rcu_barrier_callback(struct rcu_head *rhp)
-{
- struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head);
- struct rcu_state *rsp = rdp->rsp;
-
- if (atomic_dec_and_test(&rsp->barrier_cpu_count)) {
- _rcu_barrier_trace(rsp, "LastCB", -1, rsp->n_barrier_done);
- complete(&rsp->barrier_completion);
- } else {
- _rcu_barrier_trace(rsp, "CB", -1, rsp->n_barrier_done);
- }
-}
-
-/*
- * Called with preemption disabled, and from cross-cpu IRQ context.
- */
-static void rcu_barrier_func(void *type)
-{
- struct rcu_state *rsp = type;
- struct rcu_data *rdp = __this_cpu_ptr(rsp->rda);
-
- _rcu_barrier_trace(rsp, "IRQ", -1, rsp->n_barrier_done);
- atomic_inc(&rsp->barrier_cpu_count);
- rsp->call(&rdp->barrier_head, rcu_barrier_callback);
-}
-
-/*
- * Orchestrate the specified type of RCU barrier, waiting for all
- * RCU callbacks of the specified type to complete.
- */
-static void _rcu_barrier(struct rcu_state *rsp)
-{
- int cpu;
- struct rcu_data *rdp;
- unsigned long snap = ACCESS_ONCE(rsp->n_barrier_done);
- unsigned long snap_done;
-
- _rcu_barrier_trace(rsp, "Begin", -1, snap);
-
- /* Take mutex to serialize concurrent rcu_barrier() requests. */
- mutex_lock(&rsp->barrier_mutex);
-
- /*
- * Ensure that all prior references, including to ->n_barrier_done,
- * are ordered before the _rcu_barrier() machinery.
- */
- smp_mb(); /* See above block comment. */
-
- /*
- * Recheck ->n_barrier_done to see if others did our work for us.
- * This means checking ->n_barrier_done for an even-to-odd-to-even
- * transition. The "if" expression below therefore rounds the old
- * value up to the next even number and adds two before comparing.
- */
- snap_done = rsp->n_barrier_done;
- _rcu_barrier_trace(rsp, "Check", -1, snap_done);
-
- /*
- * If the value in snap is odd, we needed to wait for the current
- * rcu_barrier() to complete, then wait for the next one, in other
- * words, we need the value of snap_done to be three larger than
- * the value of snap. On the other hand, if the value in snap is
- * even, we only had to wait for the next rcu_barrier() to complete,
- * in other words, we need the value of snap_done to be only two
- * greater than the value of snap. The "(snap + 3) & ~0x1" computes
- * this for us (thank you, Linus!).
- */
- if (ULONG_CMP_GE(snap_done, (snap + 3) & ~0x1)) {
- _rcu_barrier_trace(rsp, "EarlyExit", -1, snap_done);
- smp_mb(); /* caller's subsequent code after above check. */
- mutex_unlock(&rsp->barrier_mutex);
- return;
- }
-
- /*
- * Increment ->n_barrier_done to avoid duplicate work. Use
- * ACCESS_ONCE() to prevent the compiler from speculating
- * the increment to precede the early-exit check.
- */
- ACCESS_ONCE(rsp->n_barrier_done)++;
- WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 1);
- _rcu_barrier_trace(rsp, "Inc1", -1, rsp->n_barrier_done);
- smp_mb(); /* Order ->n_barrier_done increment with below mechanism. */
-
- /*
- * Initialize the count to one rather than to zero in order to
- * avoid a too-soon return to zero in case of a short grace period
- * (or preemption of this task). Exclude CPU-hotplug operations
- * to ensure that no offline CPU has callbacks queued.
- */
- init_completion(&rsp->barrier_completion);
- atomic_set(&rsp->barrier_cpu_count, 1);
- get_online_cpus();
-
- /*
- * Force each CPU with callbacks to register a new callback.
- * When that callback is invoked, we will know that all of the
- * corresponding CPU's preceding callbacks have been invoked.
- */
- for_each_possible_cpu(cpu) {
- if (!cpu_online(cpu) && !rcu_is_nocb_cpu(cpu))
- continue;
- rdp = per_cpu_ptr(rsp->rda, cpu);
- if (rcu_is_nocb_cpu(cpu)) {
- _rcu_barrier_trace(rsp, "OnlineNoCB", cpu,
- rsp->n_barrier_done);
- atomic_inc(&rsp->barrier_cpu_count);
- __call_rcu(&rdp->barrier_head, rcu_barrier_callback,
- rsp, cpu, 0);
- } else if (ACCESS_ONCE(rdp->qlen)) {
- _rcu_barrier_trace(rsp, "OnlineQ", cpu,
- rsp->n_barrier_done);
- smp_call_function_single(cpu, rcu_barrier_func, rsp, 1);
- } else {
- _rcu_barrier_trace(rsp, "OnlineNQ", cpu,
- rsp->n_barrier_done);
- }
- }
- put_online_cpus();
-
- /*
- * Now that we have an rcu_barrier_callback() callback on each
- * CPU, and thus each counted, remove the initial count.
- */
- if (atomic_dec_and_test(&rsp->barrier_cpu_count))
- complete(&rsp->barrier_completion);
-
- /* Increment ->n_barrier_done to prevent duplicate work. */
- smp_mb(); /* Keep increment after above mechanism. */
- ACCESS_ONCE(rsp->n_barrier_done)++;
- WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 0);
- _rcu_barrier_trace(rsp, "Inc2", -1, rsp->n_barrier_done);
- smp_mb(); /* Keep increment before caller's subsequent code. */
-
- /* Wait for all rcu_barrier_callback() callbacks to be invoked. */
- wait_for_completion(&rsp->barrier_completion);
-
- /* Other rcu_barrier() invocations can now safely proceed. */
- mutex_unlock(&rsp->barrier_mutex);
-}
-
-/**
- * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
- */
-void rcu_barrier_bh(void)
-{
- _rcu_barrier(&rcu_bh_state);
-}
-EXPORT_SYMBOL_GPL(rcu_barrier_bh);
-
-/**
- * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
- */
-void rcu_barrier_sched(void)
-{
- _rcu_barrier(&rcu_sched_state);
-}
-EXPORT_SYMBOL_GPL(rcu_barrier_sched);
-
-/*
- * Do boot-time initialization of a CPU's per-CPU RCU data.
- */
-static void __init
-rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
-{
- unsigned long flags;
- struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
- struct rcu_node *rnp = rcu_get_root(rsp);
-
- /* Set up local state, ensuring consistent view of global state. */
- raw_spin_lock_irqsave(&rnp->lock, flags);
- rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo);
- init_callback_list(rdp);
- rdp->qlen_lazy = 0;
- ACCESS_ONCE(rdp->qlen) = 0;
- rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
- WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE);
- WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
- rdp->cpu = cpu;
- rdp->rsp = rsp;
- rcu_boot_init_nocb_percpu_data(rdp);
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
-}
-
-/*
- * Initialize a CPU's per-CPU RCU data. Note that only one online or
- * offline event can be happening at a given time. Note also that we
- * can accept some slop in the rsp->completed access due to the fact
- * that this CPU cannot possibly have any RCU callbacks in flight yet.
- */
-static void
-rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
-{
- unsigned long flags;
- unsigned long mask;
- struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
- struct rcu_node *rnp = rcu_get_root(rsp);
-
- /* Exclude new grace periods. */
- mutex_lock(&rsp->onoff_mutex);
-
- /* Set up local state, ensuring consistent view of global state. */
- raw_spin_lock_irqsave(&rnp->lock, flags);
- rdp->beenonline = 1; /* We have now been online. */
- rdp->preemptible = preemptible;
- rdp->qlen_last_fqs_check = 0;
- rdp->n_force_qs_snap = rsp->n_force_qs;
- rdp->blimit = blimit;
- init_callback_list(rdp); /* Re-enable callbacks on this CPU. */
- rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
- rcu_sysidle_init_percpu_data(rdp->dynticks);
- atomic_set(&rdp->dynticks->dynticks,
- (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1);
- raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
-
- /* Add CPU to rcu_node bitmasks. */
- rnp = rdp->mynode;
- mask = rdp->grpmask;
- do {
- /* Exclude any attempts to start a new GP on small systems. */
- raw_spin_lock(&rnp->lock); /* irqs already disabled. */
- rnp->qsmaskinit |= mask;
- mask = rnp->grpmask;
- if (rnp == rdp->mynode) {
- /*
- * If there is a grace period in progress, we will
- * set up to wait for it next time we run the
- * RCU core code.
- */
- rdp->gpnum = rnp->completed;
- rdp->completed = rnp->completed;
- rdp->passed_quiesce = 0;
- rdp->qs_pending = 0;
- trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl"));
- }
- raw_spin_unlock(&rnp->lock); /* irqs already disabled. */
- rnp = rnp->parent;
- } while (rnp != NULL && !(rnp->qsmaskinit & mask));
- local_irq_restore(flags);
-
- mutex_unlock(&rsp->onoff_mutex);
-}
-
-static void rcu_prepare_cpu(int cpu)
-{
- struct rcu_state *rsp;
-
- for_each_rcu_flavor(rsp)
- rcu_init_percpu_data(cpu, rsp,
- strcmp(rsp->name, "rcu_preempt") == 0);
-}
-
-/*
- * Handle CPU online/offline notification events.
- */
-static int rcu_cpu_notify(struct notifier_block *self,
- unsigned long action, void *hcpu)
-{
- long cpu = (long)hcpu;
- struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
- struct rcu_node *rnp = rdp->mynode;
- struct rcu_state *rsp;
-
- trace_rcu_utilization(TPS("Start CPU hotplug"));
- switch (action) {
- case CPU_UP_PREPARE:
- case CPU_UP_PREPARE_FROZEN:
- rcu_prepare_cpu(cpu);
- rcu_prepare_kthreads(cpu);
- break;
- case CPU_ONLINE:
- case CPU_DOWN_FAILED:
- rcu_boost_kthread_setaffinity(rnp, -1);
- break;
- case CPU_DOWN_PREPARE:
- rcu_boost_kthread_setaffinity(rnp, cpu);
- break;
- case CPU_DYING:
- case CPU_DYING_FROZEN:
- for_each_rcu_flavor(rsp)
- rcu_cleanup_dying_cpu(rsp);
- break;
- case CPU_DEAD:
- case CPU_DEAD_FROZEN:
- case CPU_UP_CANCELED:
- case CPU_UP_CANCELED_FROZEN:
- for_each_rcu_flavor(rsp)
- rcu_cleanup_dead_cpu(cpu, rsp);
- break;
- default:
- break;
- }
- trace_rcu_utilization(TPS("End CPU hotplug"));
- return NOTIFY_OK;
-}
-
-static int rcu_pm_notify(struct notifier_block *self,
- unsigned long action, void *hcpu)
-{
- switch (action) {
- case PM_HIBERNATION_PREPARE:
- case PM_SUSPEND_PREPARE:
- if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */
- rcu_expedited = 1;
- break;
- case PM_POST_HIBERNATION:
- case PM_POST_SUSPEND:
- rcu_expedited = 0;
- break;
- default:
- break;
- }
- return NOTIFY_OK;
-}
-
-/*
- * Spawn the kthread that handles this RCU flavor's grace periods.
- */
-static int __init rcu_spawn_gp_kthread(void)
-{
- unsigned long flags;
- struct rcu_node *rnp;
- struct rcu_state *rsp;
- struct task_struct *t;
-
- for_each_rcu_flavor(rsp) {
- t = kthread_run(rcu_gp_kthread, rsp, "%s", rsp->name);
- BUG_ON(IS_ERR(t));
- rnp = rcu_get_root(rsp);
- raw_spin_lock_irqsave(&rnp->lock, flags);
- rsp->gp_kthread = t;
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- rcu_spawn_nocb_kthreads(rsp);
- }
- return 0;
-}
-early_initcall(rcu_spawn_gp_kthread);
-
-/*
- * This function is invoked towards the end of the scheduler's initialization
- * process. Before this is called, the idle task might contain
- * RCU read-side critical sections (during which time, this idle
- * task is booting the system). After this function is called, the
- * idle tasks are prohibited from containing RCU read-side critical
- * sections. This function also enables RCU lockdep checking.
- */
-void rcu_scheduler_starting(void)
-{
- WARN_ON(num_online_cpus() != 1);
- WARN_ON(nr_context_switches() > 0);
- rcu_scheduler_active = 1;
-}
-
-/*
- * Compute the per-level fanout, either using the exact fanout specified
- * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT.
- */
-#ifdef CONFIG_RCU_FANOUT_EXACT
-static void __init rcu_init_levelspread(struct rcu_state *rsp)
-{
- int i;
-
- for (i = rcu_num_lvls - 1; i > 0; i--)
- rsp->levelspread[i] = CONFIG_RCU_FANOUT;
- rsp->levelspread[0] = rcu_fanout_leaf;
-}
-#else /* #ifdef CONFIG_RCU_FANOUT_EXACT */
-static void __init rcu_init_levelspread(struct rcu_state *rsp)
-{
- int ccur;
- int cprv;
- int i;
-
- cprv = nr_cpu_ids;
- for (i = rcu_num_lvls - 1; i >= 0; i--) {
- ccur = rsp->levelcnt[i];
- rsp->levelspread[i] = (cprv + ccur - 1) / ccur;
- cprv = ccur;
- }
-}
-#endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */
-
-/*
- * Helper function for rcu_init() that initializes one rcu_state structure.
- */
-static void __init rcu_init_one(struct rcu_state *rsp,
- struct rcu_data __percpu *rda)
-{
- static char *buf[] = { "rcu_node_0",
- "rcu_node_1",
- "rcu_node_2",
- "rcu_node_3" }; /* Match MAX_RCU_LVLS */
- static char *fqs[] = { "rcu_node_fqs_0",
- "rcu_node_fqs_1",
- "rcu_node_fqs_2",
- "rcu_node_fqs_3" }; /* Match MAX_RCU_LVLS */
- int cpustride = 1;
- int i;
- int j;
- struct rcu_node *rnp;
-
- BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */
-
- /* Silence gcc 4.8 warning about array index out of range. */
- if (rcu_num_lvls > RCU_NUM_LVLS)
- panic("rcu_init_one: rcu_num_lvls overflow");
-
- /* Initialize the level-tracking arrays. */
-
- for (i = 0; i < rcu_num_lvls; i++)
- rsp->levelcnt[i] = num_rcu_lvl[i];
- for (i = 1; i < rcu_num_lvls; i++)
- rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1];
- rcu_init_levelspread(rsp);
-
- /* Initialize the elements themselves, starting from the leaves. */
-
- for (i = rcu_num_lvls - 1; i >= 0; i--) {
- cpustride *= rsp->levelspread[i];
- rnp = rsp->level[i];
- for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) {
- raw_spin_lock_init(&rnp->lock);
- lockdep_set_class_and_name(&rnp->lock,
- &rcu_node_class[i], buf[i]);
- raw_spin_lock_init(&rnp->fqslock);
- lockdep_set_class_and_name(&rnp->fqslock,
- &rcu_fqs_class[i], fqs[i]);
- rnp->gpnum = rsp->gpnum;
- rnp->completed = rsp->completed;
- rnp->qsmask = 0;
- rnp->qsmaskinit = 0;
- rnp->grplo = j * cpustride;
- rnp->grphi = (j + 1) * cpustride - 1;
- if (rnp->grphi >= NR_CPUS)
- rnp->grphi = NR_CPUS - 1;
- if (i == 0) {
- rnp->grpnum = 0;
- rnp->grpmask = 0;
- rnp->parent = NULL;
- } else {
- rnp->grpnum = j % rsp->levelspread[i - 1];
- rnp->grpmask = 1UL << rnp->grpnum;
- rnp->parent = rsp->level[i - 1] +
- j / rsp->levelspread[i - 1];
- }
- rnp->level = i;
- INIT_LIST_HEAD(&rnp->blkd_tasks);
- rcu_init_one_nocb(rnp);
- }
- }
-
- rsp->rda = rda;
- init_waitqueue_head(&rsp->gp_wq);
- init_irq_work(&rsp->wakeup_work, rsp_wakeup);
- rnp = rsp->level[rcu_num_lvls - 1];
- for_each_possible_cpu(i) {
- while (i > rnp->grphi)
- rnp++;
- per_cpu_ptr(rsp->rda, i)->mynode = rnp;
- rcu_boot_init_percpu_data(i, rsp);
- }
- list_add(&rsp->flavors, &rcu_struct_flavors);
-}
-
-/*
- * Compute the rcu_node tree geometry from kernel parameters. This cannot
- * replace the definitions in rcutree.h because those are needed to size
- * the ->node array in the rcu_state structure.
- */
-static void __init rcu_init_geometry(void)
-{
- ulong d;
- int i;
- int j;
- int n = nr_cpu_ids;
- int rcu_capacity[MAX_RCU_LVLS + 1];
-
- /*
- * Initialize any unspecified boot parameters.
- * The default values of jiffies_till_first_fqs and
- * jiffies_till_next_fqs are set to the RCU_JIFFIES_TILL_FORCE_QS
- * value, which is a function of HZ, then adding one for each
- * RCU_JIFFIES_FQS_DIV CPUs that might be on the system.
- */
- d = RCU_JIFFIES_TILL_FORCE_QS + nr_cpu_ids / RCU_JIFFIES_FQS_DIV;
- if (jiffies_till_first_fqs == ULONG_MAX)
- jiffies_till_first_fqs = d;
- if (jiffies_till_next_fqs == ULONG_MAX)
- jiffies_till_next_fqs = d;
-
- /* If the compile-time values are accurate, just leave. */
- if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF &&
- nr_cpu_ids == NR_CPUS)
- return;
-
- /*
- * Compute number of nodes that can be handled an rcu_node tree
- * with the given number of levels. Setting rcu_capacity[0] makes
- * some of the arithmetic easier.
- */
- rcu_capacity[0] = 1;
- rcu_capacity[1] = rcu_fanout_leaf;
- for (i = 2; i <= MAX_RCU_LVLS; i++)
- rcu_capacity[i] = rcu_capacity[i - 1] * CONFIG_RCU_FANOUT;
-
- /*
- * The boot-time rcu_fanout_leaf parameter is only permitted
- * to increase the leaf-level fanout, not decrease it. Of course,
- * the leaf-level fanout cannot exceed the number of bits in
- * the rcu_node masks. Finally, the tree must be able to accommodate
- * the configured number of CPUs. Complain and fall back to the
- * compile-time values if these limits are exceeded.
- */
- if (rcu_fanout_leaf < CONFIG_RCU_FANOUT_LEAF ||
- rcu_fanout_leaf > sizeof(unsigned long) * 8 ||
- n > rcu_capacity[MAX_RCU_LVLS]) {
- WARN_ON(1);
- return;
- }
-
- /* Calculate the number of rcu_nodes at each level of the tree. */
- for (i = 1; i <= MAX_RCU_LVLS; i++)
- if (n <= rcu_capacity[i]) {
- for (j = 0; j <= i; j++)
- num_rcu_lvl[j] =
- DIV_ROUND_UP(n, rcu_capacity[i - j]);
- rcu_num_lvls = i;
- for (j = i + 1; j <= MAX_RCU_LVLS; j++)
- num_rcu_lvl[j] = 0;
- break;
- }
-
- /* Calculate the total number of rcu_node structures. */
- rcu_num_nodes = 0;
- for (i = 0; i <= MAX_RCU_LVLS; i++)
- rcu_num_nodes += num_rcu_lvl[i];
- rcu_num_nodes -= n;
-}
-
-void __init rcu_init(void)
-{
- int cpu;
-
- rcu_bootup_announce();
- rcu_init_geometry();
- rcu_init_one(&rcu_bh_state, &rcu_bh_data);
- rcu_init_one(&rcu_sched_state, &rcu_sched_data);
- __rcu_init_preempt();
- open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
-
- /*
- * We don't need protection against CPU-hotplug here because
- * this is called early in boot, before either interrupts
- * or the scheduler are operational.
- */
- cpu_notifier(rcu_cpu_notify, 0);
- pm_notifier(rcu_pm_notify, 0);
- for_each_online_cpu(cpu)
- rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
-}
-
-#include "rcutree_plugin.h"