diff options
| -rw-r--r-- | Documentation/atomic_ops.txt | 2 | ||||
| -rw-r--r-- | Documentation/memory-barriers.txt | 1 | ||||
| -rw-r--r-- | include/linux/rcupdate.h | 15 | ||||
| -rw-r--r-- | include/linux/srcu.h | 26 | ||||
| -rw-r--r-- | include/trace/events/rcu.h | 31 | ||||
| -rw-r--r-- | init/Kconfig | 12 | ||||
| -rw-r--r-- | kernel/context_tracking.c | 75 | ||||
| -rw-r--r-- | kernel/rcu.h | 7 | ||||
| -rw-r--r-- | kernel/rcupdate.c | 60 | ||||
| -rw-r--r-- | kernel/rcutiny.c | 8 | ||||
| -rw-r--r-- | kernel/rcutiny_plugin.h | 56 | ||||
| -rw-r--r-- | kernel/rcutorture.c | 66 | ||||
| -rw-r--r-- | kernel/rcutree.c | 260 | ||||
| -rw-r--r-- | kernel/rcutree.h | 11 | ||||
| -rw-r--r-- | kernel/srcu.c | 37 | ||||
| -rw-r--r-- | kernel/trace/trace_clock.c | 1 | ||||
| -rw-r--r-- | lib/Kconfig.debug | 117 |
17 files changed, 556 insertions, 229 deletions
diff --git a/Documentation/atomic_ops.txt b/Documentation/atomic_ops.txt index 27f2b21a9d5c..d9ca5be9b471 100644 --- a/Documentation/atomic_ops.txt +++ b/Documentation/atomic_ops.txt @@ -253,6 +253,8 @@ This performs an atomic exchange operation on the atomic variable v, setting the given new value. It returns the old value that the atomic variable v had just before the operation. +atomic_xchg requires explicit memory barriers around the operation. + int atomic_cmpxchg(atomic_t *v, int old, int new); This performs an atomic compare exchange operation on the atomic value v, diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt index 3c4e1b3b80a1..fa5d8a9ae205 100644 --- a/Documentation/memory-barriers.txt +++ b/Documentation/memory-barriers.txt @@ -1685,6 +1685,7 @@ explicit lock operations, described later). These include: xchg(); cmpxchg(); + atomic_xchg(); atomic_cmpxchg(); atomic_inc_return(); atomic_dec_return(); diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 275aa3f1062d..b758ce17b309 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -53,7 +53,10 @@ extern int rcutorture_runnable; /* for sysctl */ extern void rcutorture_record_test_transition(void); extern void rcutorture_record_progress(unsigned long vernum); extern void do_trace_rcu_torture_read(char *rcutorturename, - struct rcu_head *rhp); + struct rcu_head *rhp, + unsigned long secs, + unsigned long c_old, + unsigned long c); #else static inline void rcutorture_record_test_transition(void) { @@ -63,9 +66,13 @@ static inline void rcutorture_record_progress(unsigned long vernum) } #ifdef CONFIG_RCU_TRACE extern void do_trace_rcu_torture_read(char *rcutorturename, - struct rcu_head *rhp); + struct rcu_head *rhp, + unsigned long secs, + unsigned long c_old, + unsigned long c); #else -#define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0) +#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ + do { } while (0) #endif #endif @@ -749,7 +756,7 @@ static inline void rcu_preempt_sleep_check(void) * preemptible RCU implementations (TREE_PREEMPT_RCU and TINY_PREEMPT_RCU) * in CONFIG_PREEMPT kernel builds, RCU read-side critical sections may * be preempted, but explicit blocking is illegal. Finally, in preemptible - * RCU implementations in real-time (CONFIG_PREEMPT_RT) kernel builds, + * RCU implementations in real-time (with -rt patchset) kernel builds, * RCU read-side critical sections may be preempted and they may also * block, but only when acquiring spinlocks that are subject to priority * inheritance. diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 6eb691b08358..04f4121a23ae 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -151,30 +151,14 @@ void srcu_barrier(struct srcu_struct *sp); * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot * and while lockdep is disabled. * - * Note that if the CPU is in the idle loop from an RCU point of view - * (ie: that we are in the section between rcu_idle_enter() and - * rcu_idle_exit()) then srcu_read_lock_held() returns false even if - * the CPU did an srcu_read_lock(). The reason for this is that RCU - * ignores CPUs that are in such a section, considering these as in - * extended quiescent state, so such a CPU is effectively never in an - * RCU read-side critical section regardless of what RCU primitives it - * invokes. This state of affairs is required --- we need to keep an - * RCU-free window in idle where the CPU may possibly enter into low - * power mode. This way we can notice an extended quiescent state to - * other CPUs that started a grace period. Otherwise we would delay any - * grace period as long as we run in the idle task. - * - * Similarly, we avoid claiming an SRCU read lock held if the current - * CPU is offline. + * Note that SRCU is based on its own statemachine and it doesn't + * relies on normal RCU, it can be called from the CPU which + * is in the idle loop from an RCU point of view or offline. */ static inline int srcu_read_lock_held(struct srcu_struct *sp) { if (!debug_lockdep_rcu_enabled()) return 1; - if (rcu_is_cpu_idle()) - return 0; - if (!rcu_lockdep_current_cpu_online()) - return 0; return lock_is_held(&sp->dep_map); } @@ -236,8 +220,6 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) int retval = __srcu_read_lock(sp); rcu_lock_acquire(&(sp)->dep_map); - rcu_lockdep_assert(!rcu_is_cpu_idle(), - "srcu_read_lock() used illegally while idle"); return retval; } @@ -251,8 +233,6 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) static inline void srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp) { - rcu_lockdep_assert(!rcu_is_cpu_idle(), - "srcu_read_unlock() used illegally while idle"); rcu_lock_release(&(sp)->dep_map); __srcu_read_unlock(sp, idx); } diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index d4f559b1ec34..1918e832da4f 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -44,8 +44,10 @@ TRACE_EVENT(rcu_utilization, * of a new grace period or the end of an old grace period ("cpustart" * and "cpuend", respectively), a CPU passing through a quiescent * state ("cpuqs"), a CPU coming online or going offline ("cpuonl" - * and "cpuofl", respectively), and a CPU being kicked for being too - * long in dyntick-idle mode ("kick"). + * and "cpuofl", respectively), a CPU being kicked for being too + * long in dyntick-idle mode ("kick"), a CPU accelerating its new + * callbacks to RCU_NEXT_READY_TAIL ("AccReadyCB"), and a CPU + * accelerating its new callbacks to RCU_WAIT_TAIL ("AccWaitCB"). */ TRACE_EVENT(rcu_grace_period, @@ -393,7 +395,7 @@ TRACE_EVENT(rcu_kfree_callback, */ TRACE_EVENT(rcu_batch_start, - TP_PROTO(char *rcuname, long qlen_lazy, long qlen, int blimit), + TP_PROTO(char *rcuname, long qlen_lazy, long qlen, long blimit), TP_ARGS(rcuname, qlen_lazy, qlen, blimit), @@ -401,7 +403,7 @@ TRACE_EVENT(rcu_batch_start, __field(char *, rcuname) __field(long, qlen_lazy) __field(long, qlen) - __field(int, blimit) + __field(long, blimit) ), TP_fast_assign( @@ -411,7 +413,7 @@ TRACE_EVENT(rcu_batch_start, __entry->blimit = blimit; ), - TP_printk("%s CBs=%ld/%ld bl=%d", + TP_printk("%s CBs=%ld/%ld bl=%ld", __entry->rcuname, __entry->qlen_lazy, __entry->qlen, __entry->blimit) ); @@ -523,22 +525,30 @@ TRACE_EVENT(rcu_batch_end, */ TRACE_EVENT(rcu_torture_read, - TP_PROTO(char *rcutorturename, struct rcu_head *rhp), + TP_PROTO(char *rcutorturename, struct rcu_head *rhp, + unsigned long secs, unsigned long c_old, unsigned long c), - TP_ARGS(rcutorturename, rhp), + TP_ARGS(rcutorturename, rhp, secs, c_old, c), TP_STRUCT__entry( __field(char *, rcutorturename) __field(struct rcu_head *, rhp) + __field(unsigned long, secs) + __field(unsigned long, c_old) + __field(unsigned long, c) ), TP_fast_assign( __entry->rcutorturename = rcutorturename; __entry->rhp = rhp; + __entry->secs = secs; + __entry->c_old = c_old; + __entry->c = c; ), - TP_printk("%s torture read %p", - __entry->rcutorturename, __entry->rhp) + TP_printk("%s torture read %p %luus c: %lu %lu", + __entry->rcutorturename, __entry->rhp, + __entry->secs, __entry->c_old, __entry->c) ); /* @@ -608,7 +618,8 @@ TRACE_EVENT(rcu_barrier, #define trace_rcu_invoke_kfree_callback(rcuname, rhp, offset) do { } while (0) #define trace_rcu_batch_end(rcuname, callbacks_invoked, cb, nr, iit, risk) \ do { } while (0) -#define trace_rcu_torture_read(rcutorturename, rhp) do { } while (0) +#define trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ + do { } while (0) #define trace_rcu_barrier(name, s, cpu, cnt, done) do { } while (0) #endif /* #else #ifdef CONFIG_RCU_TRACE */ diff --git a/init/Kconfig b/init/Kconfig index be8b7f55312d..b023334df142 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -453,7 +453,7 @@ config TREE_RCU config TREE_PREEMPT_RCU bool "Preemptible tree-based hierarchical RCU" - depends on PREEMPT && SMP + depends on PREEMPT help This option selects the RCU implementation that is designed for very large SMP systems with hundreds or @@ -461,6 +461,8 @@ config TREE_PREEMPT_RCU is also required. It also scales down nicely to smaller systems. + Select this option if you are unsure. + config TINY_RCU bool "UP-only small-memory-footprint RCU" depends on !PREEMPT && !SMP @@ -486,6 +488,14 @@ config PREEMPT_RCU This option enables preemptible-RCU code that is common between the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations. +config RCU_STALL_COMMON + def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE ) + help + This option enables RCU CPU stall code that is common between + the TINY and TREE variants of RCU. The purpose is to allow + the tiny variants to disable RCU CPU stall warnings, while + making these warnings mandatory for the tree variants. + config CONTEXT_TRACKING bool diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index e0e07fd55508..d566aba7e801 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -1,3 +1,19 @@ +/* + * Context tracking: Probe on high level context boundaries such as kernel + * and userspace. This includes syscalls and exceptions entry/exit. + * + * This is used by RCU to remove its dependency on the timer tick while a CPU + * runs in userspace. + * + * Started by Frederic Weisbecker: + * + * Copyright (C) 2012 Red Hat, Inc., Frederic Weisbecker <fweisbec@redhat.com> + * + * Many thanks to Gilad Ben-Yossef, Paul McKenney, Ingo Molnar, Andrew Morton, + * Steven Rostedt, Peter Zijlstra for suggestions and improvements. + * + */ + #include <linux/context_tracking.h> #include <linux/rcupdate.h> #include <linux/sched.h> @@ -6,8 +22,8 @@ struct context_tracking { /* - * When active is false, hooks are not set to - * minimize overhead: TIF flags are cleared + * When active is false, probes are unset in order + * to minimize overhead: TIF flags are cleared * and calls to user_enter/exit are ignored. This * may be further optimized using static keys. */ @@ -24,6 +40,15 @@ static DEFINE_PER_CPU(struct context_tracking, context_tracking) = { #endif }; +/** + * user_enter - Inform the context tracking that the CPU is going to + * enter userspace mode. + * + * This function must be called right before we switch from the kernel + * to userspace, when it's guaranteed the remaining kernel instructions + * to execute won't use any RCU read side critical section because this + * function sets RCU in extended quiescent state. + */ void user_enter(void) { unsigned long flags; @@ -39,40 +64,70 @@ void user_enter(void) if (in_interrupt()) return; + /* Kernel threads aren't supposed to go to userspace */ WARN_ON_ONCE(!current->mm); local_irq_save(flags); if (__this_cpu_read(context_tracking.active) && __this_cpu_read(context_tracking.state) != IN_USER) { __this_cpu_write(context_tracking.state, IN_USER); + /* + * At this stage, only low level arch entry code remains and + * then we'll run in userspace. We can assume there won't be + * any RCU read-side critical section until the next call to + * user_exit() or rcu_irq_enter(). Let's remove RCU's dependency + * on the tick. + */ rcu_user_enter(); } local_irq_restore(flags); } + +/** + * user_exit - Inform the context tracking that the CPU is + * exiting userspace mode and entering the kernel. + * + * This function must be called after we entered the kernel from userspace + * before any use of RCU read side critical section. This potentially include + * any high level kernel code like syscalls, exceptions, signal handling, etc... + * + * This call supports re-entrancy. This way it can be called from any exception + * handler without needing to know if we came from userspace or not. + */ void user_exit(void) { unsigned long flags; - /* - * Some contexts may involve an exception occuring in an irq, - * leading to that nesting: - * rcu_irq_enter() rcu_user_exit() rcu_user_exit() rcu_irq_exit() - * This would mess up the dyntick_nesting count though. And rcu_irq_*() - * helpers are enough to protect RCU uses inside the exception. So - * just return immediately if we detect we are in an IRQ. - */ if (in_interrupt()) return; local_irq_save(flags); if (__this_cpu_read(context_tracking.state) == IN_USER) { __this_cpu_write(context_tracking.state, IN_KERNEL); + /* + * We are going to run code that may use RCU. Inform + * RCU core about that (ie: we may need the tick again). + */ rcu_user_exit(); } local_irq_restore(flags); } + +/** + * context_tracking_task_switch - context switch the syscall callbacks + * @prev: the task that is being switched out + * @next: the task that is being switched in + * + * The context tracking uses the syscall slow path to implement its user-kernel + * boundaries probes on syscalls. This way it doesn't impact the syscall fast + * path on CPUs that don't do context tracking. + * + * But we need to clear the flag on the previous task because it may later + * migrate to some CPU that doesn't do the context tracking. As such the TIF + * flag may not be desired there. + */ void context_tracking_task_switch(struct task_struct *prev, struct task_struct *next) { diff --git a/kernel/rcu.h b/kernel/rcu.h index 20dfba576c2b..7f8e7590e3e5 100644 --- a/kernel/rcu.h +++ b/kernel/rcu.h @@ -111,4 +111,11 @@ static inline bool __rcu_reclaim(char *rn, struct rcu_head *head) extern int rcu_expedited; +#ifdef CONFIG_RCU_STALL_COMMON + +extern int rcu_cpu_stall_suppress; +int rcu_jiffies_till_stall_check(void); + +#endif /* #ifdef CONFIG_RCU_STALL_COMMON */ + #endif /* __LINUX_RCU_H */ diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index a2cf76177b44..48ab70384a4c 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -404,11 +404,65 @@ EXPORT_SYMBOL_GPL(rcuhead_debug_descr); #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE) -void do_trace_rcu_torture_read(char *rcutorturename, struct rcu_head *rhp) +void do_trace_rcu_torture_read(char *rcutorturename, struct rcu_head *rhp, + unsigned long secs, + unsigned long c_old, unsigned long c) { - trace_rcu_torture_read(rcutorturename, rhp); + trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c); } EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read); #else -#define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0) +#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ + do { } while (0) #endif + +#ifdef CONFIG_RCU_STALL_COMMON + +#ifdef CONFIG_PROVE_RCU +#define RCU_STALL_DELAY_DELTA (5 * HZ) +#else +#define RCU_STALL_DELAY_DELTA 0 +#endif + +int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */ +int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT; + +module_param(rcu_cpu_stall_suppress, int, 0644); +module_param(rcu_cpu_stall_timeout, int, 0644); + +int rcu_jiffies_till_stall_check(void) +{ + int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout); + + /* + * Limit check must be consistent with the Kconfig limits + * for CONFIG_RCU_CPU_STALL_TIMEOUT. + */ + if (till_stall_check < 3) { + ACCESS_ONCE(rcu_cpu_stall_timeout) = 3; + till_stall_check = 3; + } else if (till_stall_check > 300) { + ACCESS_ONCE(rcu_cpu_stall_timeout) = 300; + till_stall_check = 300; + } + return till_stall_check * HZ + RCU_STALL_DELAY_DELTA; +} + +static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr) +{ + rcu_cpu_stall_suppress = 1; + return NOTIFY_DONE; +} + +static struct notifier_block rcu_panic_block = { + .notifier_call = rcu_panic, +}; + +static int __init check_cpu_stall_init(void) +{ + atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block); + return 0; +} +early_initcall(check_cpu_stall_init); + +#endif /* #ifdef CONFIG_RCU_STALL_COMMON */ diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c index e7dce58f9c2a..a0714a51b6d7 100644 --- a/kernel/rcutiny.c +++ b/kernel/rcutiny.c @@ -51,10 +51,10 @@ static void __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), struct rcu_ctrlblk *rcp); -#include "rcutiny_plugin.h" - static long long rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; +#include "rcutiny_plugin.h" + /* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */ static void rcu_idle_enter_common(long long newval) { @@ -193,7 +193,7 @@ EXPORT_SYMBOL(rcu_is_cpu_idle); * interrupts don't count, we must be running at the first interrupt * level. */ -int rcu_is_cpu_rrupt_from_idle(void) +static int rcu_is_cpu_rrupt_from_idle(void) { return rcu_dynticks_nesting <= 1; } @@ -205,6 +205,7 @@ int rcu_is_cpu_rrupt_from_idle(void) */ static int rcu_qsctr_help(struct rcu_ctrlblk *rcp) { + reset_cpu_stall_ticks(rcp); if (rcp->rcucblist != NULL && rcp->donetail != rcp->curtail) { rcp->donetail = rcp->curtail; @@ -251,6 +252,7 @@ void rcu_bh_qs(int cpu) */ void rcu_check_callbacks(int cpu, int user) { + check_cpu_stalls(); if (user || rcu_is_cpu_rrupt_from_idle()) rcu_sched_qs(cpu); else if (!in_softirq()) diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h index f85016a2309b..8a233002faeb 100644 --- a/kernel/rcutiny_plugin.h +++ b/kernel/rcutiny_plugin.h @@ -33,6 +33,9 @@ struct rcu_ctrlblk { struct rcu_head **donetail; /* ->next pointer of last "done" CB. */ struct rcu_head **curtail; /* ->next pointer of last CB. */ RCU_TRACE(long qlen); /* Number of pending CBs. */ + RCU_TRACE(unsigned long gp_start); /* Start time for stalls. */ + RCU_TRACE(unsigned long ticks_this_gp); /* Statistic for stalls. */ + RCU_TRACE(unsigned long jiffies_stall); /* Jiffies at next stall. */ RCU_TRACE(char *name); /* Name of RCU type. */ }; @@ -54,6 +57,51 @@ int rcu_scheduler_active __read_mostly; EXPORT_SYMBOL_GPL(rcu_scheduler_active); #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ +#ifdef CONFIG_RCU_TRACE + +static void check_cpu_stall(struct rcu_ctrlblk *rcp) +{ + unsigned long j; + unsigned long js; + + if (rcu_cpu_stall_suppress) + return; + rcp->ticks_this_gp++; + j = jiffies; + js = rcp->jiffies_stall; + if (*rcp->curtail && ULONG_CMP_GE(j, js)) { + pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n", + rcp->name, rcp->ticks_this_gp, rcu_dynticks_nesting, + jiffies - rcp->gp_start, rcp->qlen); + dump_stack(); + } + if (*rcp->curtail && ULONG_CMP_GE(j, js)) + rcp->jiffies_stall = jiffies + + 3 * rcu_jiffies_till_stall_check() + 3; + else if (ULONG_CMP_GE(j, js)) + rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check(); +} + +static void check_cpu_stall_preempt(void); + +#endif /* #ifdef CONFIG_RCU_TRACE */ + +static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp) +{ +#ifdef CONFIG_RCU_TRACE + rcp->ticks_this_gp = 0; + rcp->gp_start = jiffies; + rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check(); +#endif /* #ifdef CONFIG_RCU_TRACE */ +} + +static void check_cpu_stalls(void) +{ + RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk)); + RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk)); + RCU_TRACE(check_cpu_stall_preempt()); +} + #ifdef CONFIG_TINY_PREEMPT_RCU #include <linux/delay.h> @@ -448,6 +496,7 @@ static void rcu_preempt_start_gp(void) /* Official start of GP. */ rcu_preempt_ctrlblk.gpnum++; RCU_TRACE(rcu_preempt_ctrlblk.n_grace_periods++); + reset_cpu_stall_ticks(&rcu_preempt_ctrlblk.rcb); /* Any blocked RCU readers block new GP. */ if (rcu_preempt_blocked_readers_any()) @@ -1054,4 +1103,11 @@ MODULE_AUTHOR("Paul E. McKenney"); MODULE_DESCRIPTION("Read-Copy Update tracing for tiny implementation"); MODULE_LICENSE("GPL"); +static void check_cpu_stall_preempt(void) +{ +#ifdef CONFIG_TINY_PREEMPT_RCU + check_cpu_stall(&rcu_preempt_ctrlblk.rcb); +#endif /* #ifdef CONFIG_TINY_PREEMPT_RCU */ +} + #endif /* #ifdef CONFIG_RCU_TRACE */ diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c index 31dea01c85fd..e1f3a8c96724 100644 --- a/kernel/rcutorture.c +++ b/kernel/rcutorture.c @@ -46,6 +46,7 @@ #include <linux/stat.h> #include <linux/srcu.h> #include <linux/slab.h> +#include <linux/trace_clock.h> #include <asm/byteorder.h> MODULE_LICENSE("GPL"); @@ -207,6 +208,20 @@ MODULE_PARM_DESC(rcutorture_runnable, "Start rcutorture at boot"); #define rcu_can_boost() 0 #endif /* #else #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */ +#ifdef CONFIG_RCU_TRACE +static u64 notrace rcu_trace_clock_local(void) +{ + u64 ts = trace_clock_local(); + unsigned long __maybe_unused ts_rem = do_div(ts, NSEC_PER_USEC); + return ts; +} +#else /* #ifdef CONFIG_RCU_TRACE */ +static u64 notrace rcu_trace_clock_local(void) +{ + return 0ULL; +} +#endif /* #else #ifdef CONFIG_RCU_TRACE */ + static unsigned long shutdown_time; /* jiffies to system shutdown. */ static unsigned long boost_starttime; /* jiffies of next boost test start. */ DEFINE_MUTEX(boost_mutex); /* protect setting boost_starttime */ @@ -845,7 +860,7 @@ static int rcu_torture_boost(void *arg) /* Wait for the next test interval. */ oldstarttime = boost_starttime; while (ULONG_CMP_LT(jiffies, oldstarttime)) { - schedule_timeout_uninterruptible(1); + schedule_timeout_interruptible(oldstarttime - jiffies); rcu_stutter_wait("rcu_torture_boost"); if (kthread_should_stop() || fullstop != FULLSTOP_DONTSTOP) @@ -1028,7 +1043,6 @@ void rcutorture_trace_dump(void) return; if (atomic_xchg(&beenhere, 1) != 0) return; - do_trace_rcu_torture_read(cur_ops->name, (struct rcu_head *)~0UL); ftrace_dump(DUMP_ALL); } @@ -1042,13 +1056,16 @@ static void rcu_torture_timer(unsigned long unused) { int idx; int completed; + int completed_end; static DEFINE_RCU_RANDOM(rand); static DEFINE_SPINLOCK(rand_lock); struct rcu_torture *p; int pipe_count; + unsigned long long ts; idx = cur_ops->readlock(); completed = cur_ops->completed(); + ts = rcu_trace_clock_local(); p = rcu_dereference_check(rcu_torture_current, rcu_read_lock_bh_held() || rcu_read_lock_sched_held() || @@ -1058,7 +1075,6 @@ static void rcu_torture_timer(unsigned long unused) cur_ops->readunlock(idx); return; } - do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu); if (p->rtort_mbtest == 0) atomic_inc(&n_rcu_torture_mberror); spin_lock(&rand_lock); @@ -1071,10 +1087,14 @@ static void rcu_torture_timer(unsigned long unused) /* Should not happen, but... */ pipe_count = RCU_TORTURE_PIPE_LEN; } - if (pipe_count > 1) + completed_end = cur_ops->completed(); + if (pipe_count > 1) { + do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu, ts, + completed, completed_end); rcutorture_trace_dump(); + } __this_cpu_inc(rcu_torture_count[pipe_count]); - completed = cur_ops->completed() - completed; + completed = completed_end - completed; if (completed > RCU_TORTURE_PIPE_LEN) { /* Should not happen, but... */ completed = RCU_TORTURE_PIPE_LEN; @@ -1094,11 +1114,13 @@ static int rcu_torture_reader(void *arg) { int completed; + int completed_end; int idx; DEFINE_RCU_RANDOM(rand); struct rcu_torture *p; int pipe_count; struct timer_list t; + unsigned long long ts; VERBOSE_PRINTK_STRING("rcu_torture_reader task started"); set_user_nice(current, 19); @@ -1112,6 +1134,7 @@ rcu_torture_reader(void *arg) } idx = cur_ops->readlock(); completed = cur_ops->completed(); + ts = rcu_trace_clock_local(); p = rcu_dereference_check(rcu_torture_current, rcu_read_lock_bh_held() || rcu_read_lock_sched_held() || @@ -1122,7 +1145,6 @@ rcu_torture_reader(void *arg) schedule_timeout_interruptible(HZ); continue; } - do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu); if (p->rtort_mbtest == 0) atomic_inc(&n_rcu_torture_mberror); cur_ops->read_delay(&rand); @@ -1132,10 +1154,14 @@ rcu_torture_reader(void *arg) /* Should not happen, but... */ pipe_count = RCU_TORTURE_PIPE_LEN; } - if (pipe_count > 1) + completed_end = cur_ops->completed(); + if (pipe_count > 1) { + do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu, + ts, completed, completed_end); rcutorture_trace_dump(); + } __this_cpu_inc(rcu_torture_count[pipe_count]); - completed = cur_ops->completed() - completed; + completed = completed_end - completed; if (completed > RCU_TORTURE_PIPE_LEN) { /* Should not happen, but... */ completed = RCU_TORTURE_PIPE_LEN; @@ -1301,19 +1327,35 @@ static void rcu_torture_shuffle_tasks(void) set_cpus_allowed_ptr(reader_tasks[i], shuffle_tmp_mask); } - if (fakewriter_tasks) { for (i = 0; i < nfakewriters; i++) if (fakewriter_tasks[i]) set_cpus_allowed_ptr(fakewriter_tasks[i], shuffle_tmp_mask); } - if (writer_task) set_cpus_allowed_ptr(writer_task, shuffle_tmp_mask); - if (stats_task) set_cpus_allowed_ptr(stats_task, shuffle_tmp_mask); + if (stutter_task) + set_cpus_allowed_ptr(stutter_task, shuffle_tmp_mask); + if (fqs_task) + set_cpus_allowed_ptr(fqs_task, shuffle_tmp_mask); + if (shutdown_task) + set_cpus_allowed_ptr(shutdown_task, shuffle_tmp_mask); +#ifdef CONFIG_HOTPLUG_CPU + if (onoff_task) + set_cpus_allowed_ptr(onoff_task, shuffle_tmp_mask); +#endif /* #ifdef CONFIG_HOTPLUG_CPU */ + if (stall_task) + set_cpus_allowed_ptr(stall_task, shuffle_tmp_mask); + if (barrier_cbs_tasks) + for (i = 0; i < n_barrier_cbs; i++) + if (barrier_cbs_tasks[i]) + set_cpus_allowed_ptr(barrier_cbs_tasks[i], + shuffle_tmp_mask); + if (barrier_task) + set_cpus_allowed_ptr(barrier_task, shuffle_tmp_mask); if (rcu_idle_cpu == -1) rcu_idle_cpu = num_online_cpus() - 1; @@ -1749,7 +1791,7 @@ static int rcu_torture_barrier_init(void) barrier_cbs_wq = kzalloc(n_barrier_cbs * sizeof(barrier_cbs_wq[0]), GFP_KERNEL); - if (barrier_cbs_tasks == NULL || barrier_cbs_wq == 0) + if (barrier_cbs_tasks == NULL || !barrier_cbs_wq) return -ENOMEM; for (i = 0; i < n_barrier_cbs; i++) { init_waitqueue_head(&barrier_cbs_wq[i]); diff --git a/kernel/rcutree.c b/kernel/rcutree.c index e441b77b614e..5b8ad827fd86 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -105,7 +105,7 @@ 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) - * optimized synchronize_sched() to a simple barrier(). When this variable + * 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. @@ -217,12 +217,6 @@ module_param(blimit, long, 0444); module_param(qhimark, long, 0444); module_param(qlowmark, long, 0444); -int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */ -int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT; - -module_param(rcu_cpu_stall_suppress, int, 0644); -module_param(rcu_cpu_stall_timeout, int, 0644); - static ulong jiffies_till_first_fqs = RCU_JIFFIES_TILL_FORCE_QS; static ulong jiffies_till_next_fqs = RCU_JIFFIES_TILL_FORCE_QS; @@ -305,17 +299,27 @@ cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) } /* - * Does the current CPU require a yet-as-unscheduled grace period? + * 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) { - struct rcu_head **ntp; + int i; - ntp = rdp->nxttail[RCU_DONE_TAIL + - (ACCESS_ONCE(rsp->completed) != rdp->completed)]; - return rdp->nxttail[RCU_DONE_TAIL] && ntp && *ntp && - !rcu_gp_in_progress(rsp); + if (rcu_gp_in_progress(rsp)) + return 0; /* No, a grace period is already in progress. */ + 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. */ } /* @@ -336,7 +340,7 @@ static struct rcu_node *rcu_get_root(struct rcu_state *rsp) static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval, bool user) { - trace_rcu_dyntick("Start", oldval, 0); + trace_rcu_dyntick("Start", oldval, rdtp->dynticks_nesting); if (!user && !is_idle_task(current)) { struct task_struct *idle = idle_task(smp_processor_id()); @@ -727,7 +731,7 @@ EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); * interrupt from idle, return true. The caller must have at least * disabled preemption. */ -int rcu_is_cpu_rrupt_from_idle(void) +static int rcu_is_cpu_rrupt_from_idle(void) { return __get_cpu_var(rcu_dynticks).dynticks_nesting <= 1; } @@ -793,28 +797,10 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) return 0; } -static int jiffies_till_stall_check(void) -{ - int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout); - - /* - * Limit check must be consistent with the Kconfig limits - * for CONFIG_RCU_CPU_STALL_TIMEOUT. - */ - if (till_stall_check < 3) { - ACCESS_ONCE(rcu_cpu_stall_timeout) = 3; - till_stall_check = 3; - } else if (till_stall_check > 300) { - ACCESS_ONCE(rcu_cpu_stall_timeout) = 300; - till_stall_check = 300; - } - return till_stall_check * HZ + RCU_STALL_DELAY_DELTA; -} - static void record_gp_stall_check_time(struct rcu_state *rsp) { rsp->gp_start = jiffies; - rsp->jiffies_stall = jiffies + jiffies_till_stall_check(); + rsp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check(); } /* @@ -857,7 +843,7 @@ static void print_other_cpu_stall(struct rcu_state *rsp) raw_spin_unlock_irqrestore(&rnp->lock, flags); return; } - rsp->jiffies_stall = jiffies + 3 * jiffies_till_stall_check() + 3; + rsp->jiffies_stall = jiffies + 3 * rcu_jiffies_till_stall_check() + 3; raw_spin_unlock_irqrestore(&rnp->lock, flags); /* @@ -935,7 +921,7 @@ static void print_cpu_stall(struct rcu_state *rsp) raw_spin_lock_irqsave(&rnp->lock, flags); if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall)) rsp->jiffies_stall = jiffies + - 3 * jiffies_till_stall_check() + 3; + 3 * rcu_jiffies_till_stall_check() + 3; raw_spin_unlock_irqrestore(&rnp->lock, flags); set_need_resched(); /* kick ourselves to get things going. */ @@ -966,12 +952,6 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) } } -static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr) -{ - rcu_cpu_stall_suppress = 1; - return NOTIFY_DONE; -} - /** * rcu_cpu_stall_reset - prevent further stall warnings in current grace period * @@ -989,15 +969,6 @@ void rcu_cpu_stall_reset(void) rsp->jiffies_stall = jiffies + ULONG_MAX / 2; } -static struct notifier_block rcu_panic_block = { - .notifier_call = rcu_panic, -}; - -static void __init check_cpu_stall_init(void) -{ - atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block); -} - /* * Update CPU-local rcu_data state to record the newly noticed grace period. * This is used both when we started the grace period and when we notice @@ -1071,6 +1042,145 @@ static void init_callback_list(struct rcu_data *rdp) } /* + * 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; +} + +/* + * 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; + } + + /* Trace depending on how much we were able to accelerate. */ + if (!*rdp->nxttail[RCU_WAIT_TAIL]) + trace_rcu_grace_period(rsp->name, rdp->gpnum, "AccWaitCB"); + else + trace_rcu_grace_period(rsp->name, rdp->gpnum, "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); +} + +/* * Advance this CPU's callbacks, but only if the current grace period * has ended. This may be called only from the CPU to whom the rdp * belongs. In addition, the corresponding leaf rcu_node structure's @@ -1080,12 +1190,15 @@ static void __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) { /* Did another grace period end? */ - if (rdp->completed != rnp->completed) { + if (rdp->completed == rnp->completed) { - /* Advance callbacks. No harm if list empty. */ - rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL]; - rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL]; - rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; + /* No, 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; @@ -1392,17 +1505,10 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags) /* * Because 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. So promote all callbacks to be - * handled after the end of the next grace period. If the - * CPU is not yet aware of the end of the previous grace period, - * we need to allow for the callback advancement that will - * occur when it does become aware. Deadlock prevents us from - * making it aware at this point: We cannot acquire a leaf - * rcu_node ->lock while holding the root rcu_node ->lock. + * by the next grace period. So this is a good place to + * assign a grace period number to recently posted callbacks. */ - rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; - if (rdp->completed == rsp->completed) - rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; + rcu_accelerate_cbs(rsp, rnp, rdp); rsp->gp_flags = RCU_GP_FLAG_INIT; raw_spin_unlock(&rnp->lock); /* Interrupts remain disabled. */ @@ -1527,7 +1633,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) * This GP can't end until cpu checks in, so all of our * callbacks can be processed during the next GP. */ - rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; + rcu_accelerate_cbs(rsp, rnp, rdp); rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */ } @@ -1779,7 +1885,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) long bl, count, count_lazy; int i; - /* If no callbacks are ready, just return.*/ + /* 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), @@ -2008,19 +2114,19 @@ __rcu_process_callbacks(struct rcu_state *rsp) WARN_ON_ONCE(rdp->beenonline == 0); - /* - * Advance callbacks in response to end of earlier grace - * period that some other CPU ended. - */ + /* Handle the end of a grace period that some other CPU ended. */ rcu_process_gp_end(rsp, rdp); /* 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_irqsave(&rcu_get_root(rsp)->lock, flags); + raw_spin_lock(&rcu_get_root(rsp)->lock); /* irqs disabled. */ rcu_start_gp(rsp, flags); /* releases above lock */ + } else { + local_irq_restore(flags); } /* If there are callbacks ready, invoke them. */ @@ -2719,9 +2825,6 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) 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); -#ifdef CONFIG_RCU_USER_QS - WARN_ON_ONCE(rdp->dynticks->in_user); -#endif rdp->cpu = cpu; rdp->rsp = rsp; rcu_boot_init_nocb_percpu_data(rdp); @@ -2938,6 +3041,10 @@ static void __init rcu_init_one(struct rcu_state *rsp, 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++) @@ -3074,7 +3181,6 @@ void __init rcu_init(void) cpu_notifier(rcu_cpu_notify, 0); for_each_online_cpu(cpu) rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); - check_cpu_stall_init(); } #include "rcutree_plugin.h" diff --git a/kernel/rcutree.h b/kernel/rcutree.h index 4b69291b093d..c896b5045d9d 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -102,10 +102,6 @@ struct rcu_dynticks { /* idle-period nonlazy_posted snapshot. */ int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */ #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */ -#ifdef CONFIG_RCU_USER_QS - bool ignore_user_qs; /* Treat userspace as extended QS or not */ - bool in_user; /* Is the CPU in userland from RCU POV? */ -#endif }; /* RCU's kthread states for tracing. */ @@ -282,6 +278,8 @@ struct rcu_data { */ struct rcu_head *nxtlist; struct rcu_head **nxttail[RCU_NEXT_SIZE]; + unsigned long nxtcompleted[RCU_NEXT_SIZE]; + /* grace periods for sublists. */ long qlen_lazy; /* # of lazy queued callbacks */ long qlen; /* # of queued callbacks, incl lazy */ long qlen_last_fqs_check; @@ -343,11 +341,6 @@ struct rcu_data { #define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */ -#ifdef CONFIG_PROVE_RCU -#define RCU_STALL_DELAY_DELTA (5 * HZ) -#else -#define RCU_STALL_DELAY_DELTA 0 -#endif #define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time */ /* to take at least one */ /* scheduling clock irq */ diff --git a/kernel/srcu.c b/kernel/srcu.c index 2b859828cdc3..01d5ccb8bfe3 100644 --- a/kernel/srcu.c +++ b/kernel/srcu.c @@ -282,12 +282,8 @@ static int srcu_readers_active(struct srcu_struct *sp) */ void cleanup_srcu_struct(struct srcu_struct *sp) { - int sum; - - sum = srcu_readers_active(sp); - WARN_ON(sum); /* Leakage unless caller handles error. */ - if (sum != 0) - return; + if (WARN_ON(srcu_readers_active(sp))) + return; /* Leakage unless caller handles error. */ free_percpu(sp->per_cpu_ref); sp->per_cpu_ref = NULL; } @@ -302,9 +298,8 @@ int __srcu_read_lock(struct srcu_struct *sp) { int idx; + idx = ACCESS_ONCE(sp->completed) & 0x1; preempt_disable(); - idx = rcu_dereference_index_check(sp->completed, - rcu_read_lock_sched_held()) & 0x1; ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->c[idx]) += 1; smp_mb(); /* B */ /* Avoid leaking the critical section. */ ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->seq[idx]) += 1; @@ -321,10 +316,8 @@ EXPORT_SYMBOL_GPL(__srcu_read_lock); */ void __srcu_read_unlock(struct srcu_struct *sp, int idx) { - preempt_disable(); smp_mb(); /* C */ /* Avoid leaking the critical section. */ - ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->c[idx]) -= 1; - preempt_enable(); + this_cpu_dec(sp->per_cpu_ref->c[idx]); } EXPORT_SYMBOL_GPL(__srcu_read_unlock); @@ -423,6 +416,7 @@ static void __synchronize_srcu(struct srcu_struct *sp, int trycount) !lock_is_held(&rcu_sched_lock_map), "Illegal synchronize_srcu() in same-type SRCU (or RCU) read-side critical section"); + might_sleep(); init_completion(&rcu.completion); head->next = NULL; @@ -455,10 +449,12 @@ static void __synchronize_srcu(struct srcu_struct *sp, int trycount) * synchronize_srcu - wait for prior SRCU read-side critical-section completion * @sp: srcu_struct with which to synchronize. * - * Flip the completed counter, and wait for the old count to drain to zero. - * As with classic RCU, the updater must use some separate means of - * synchronizing concurrent updates. Can block; must be called from - * process context. + * Wait for the count to drain to zero of both indexes. To avoid the + * possible starvation of synchronize_srcu(), it waits for the count of + * the index=((->completed & 1) ^ 1) to drain to zero at first, + * and then flip the completed and wait for the count of the other index. + * + * Can block; must be called from process context. * * Note that it is illegal to call synchronize_srcu() from the corresponding * SRCU read-side critical section; doing so will result in deadlock. @@ -480,12 +476,11 @@ EXPORT_SYMBOL_GPL(synchronize_srcu); * Wait for an SRCU grace period to elapse, but be more aggressive about * spinning rather than blocking when waiting. * - * Note that it is illegal to call this function while holding any lock - * that is acquired by a CPU-hotplug notifier. It is also illegal to call - * synchronize_srcu_expedited() from the corresponding SRCU read-side - * critical section; doing so will result in deadlock. However, it is - * perfectly legal to call synchronize_srcu_expedited() on one srcu_struct - * from some other srcu_struct's read-side critical section, as long as + * Note that it is also illegal to call synchronize_srcu_expedited() + * from the corresponding SRCU read-side critical section; + * doing so will result in deadlock. However, it is perfectly legal + * to call synchronize_srcu_expedited() on one srcu_struct from some + * other srcu_struct's read-side critical section, as long as * the resulting graph of srcu_structs is acyclic. */ void synchronize_srcu_expedited(struct srcu_struct *sp) diff --git a/kernel/trace/trace_clock.c b/kernel/trace/trace_clock.c index 394783531cbb..1bbb1b200cec 100644 --- a/kernel/trace/trace_clock.c +++ b/kernel/trace/trace_clock.c @@ -44,6 +44,7 @@ u64 notrace trace_clock_local(void) return clock; } +EXPORT_SYMBOL_GPL(trace_clock_local); /* * trace_clock(): 'between' trace clock. Not completely serialized, diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 67604e599384..a1714c897e3f 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -605,61 +605,6 @@ config PROVE_LOCKING For more details, see Documentation/lockdep-design.txt. -config PROVE_RCU - bool "RCU debugging: prove RCU correctness" - depends on PROVE_LOCKING - default n - help - This feature enables lockdep extensions that check for correct - use of RCU APIs. This is currently under development. Say Y - if you want to debug RCU usage or help work on the PROVE_RCU - feature. - - Say N if you are unsure. - -config PROVE_RCU_REPEATEDLY - bool "RCU debugging: don't disable PROVE_RCU on first splat" - depends on PROVE_RCU - default n - help - By itself, PROVE_RCU will disable checking upon issuing the - first warning (or "splat"). This feature prevents such - disabling, allowing multiple RCU-lockdep warnings to be printed - on a single reboot. - - Say Y to allow multiple RCU-lockdep warnings per boot. - - Say N if you are unsure. - -config PROVE_RCU_DELAY - bool "RCU debugging: preemptible RCU race provocation" - depends on DEBUG_KERNEL && PREEMPT_RCU - default n - help - There is a class of races that involve an unlikely preemption - of __rcu_read_unlock() just after ->rcu_read_lock_nesting has - been set to INT_MIN. This feature inserts a delay at that - point to increase the probability of these races. - - Say Y to increase probability of preemption of __rcu_read_unlock(). - - Say N if you are unsure. - -config SPARSE_RCU_POINTER - bool "RCU debugging: sparse-based checks for pointer usage" - default n - help - This feature enables the __rcu sparse annotation for - RCU-protected pointers. This annotation will cause sparse - to flag any non-RCU used of annotated pointers. This can be - helpful when debugging RCU usage. Please note that this feature - is not intended to enforce code cleanliness; it is instead merely - a debugging aid. - - Say Y to make sparse flag questionable use of RCU-protected pointers - - Say N if you are unsure. - config LOCKDEP bool depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT @@ -937,6 +882,63 @@ config BOOT_PRINTK_DELAY BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect what it believes to be lockup conditions. +menu "RCU Debugging" + +config PROVE_RCU + bool "RCU debugging: prove RCU correctness" + depends on PROVE_LOCKING + default n + help + This feature enables lockdep extensions that check for correct + use of RCU APIs. This is currently under development. Say Y + if you want to debug RCU usage or help work on the PROVE_RCU + feature. + + Say N if you are unsure. + +config PROVE_RCU_REPEATEDLY + bool "RCU debugging: don't disable PROVE_RCU on first splat" + depends on PROVE_RCU + default n + help + By itself, PROVE_RCU will disable checking upon issuing the + first warning (or "splat"). This feature prevents such + disabling, allowing multiple RCU-lockdep warnings to be printed + on a single reboot. + + Say Y to allow multiple RCU-lockdep warnings per boot. + + Say N if you are unsure. + +config PROVE_RCU_DELAY + bool "RCU debugging: preemptible RCU race provocation" + depends on DEBUG_KERNEL && PREEMPT_RCU + default n + help + There is a class of races that involve an unlikely preemption + of __rcu_read_unlock() just after ->rcu_read_lock_nesting has + been set to INT_MIN. This feature inserts a delay at that + point to increase the probability of these races. + + Say Y to increase probability of preemption of __rcu_read_unlock(). + + Say N if you are unsure. + +config SPARSE_RCU_POINTER + bool "RCU debugging: sparse-based checks for pointer usage" + default n + help + This feature enables the __rcu sparse annotation for + RCU-protected pointers. This annotation will cause sparse + to flag any non-RCU used of annotated pointers. This can be + helpful when debugging RCU usage. Please note that this feature + is not intended to enforce code cleanliness; it is instead merely + a debugging aid. + + Say Y to make sparse flag questionable use of RCU-protected pointers + + Say N if you are unsure. + config RCU_TORTURE_TEST tristate "torture tests for RCU" depends on DEBUG_KERNEL @@ -970,7 +972,7 @@ config RCU_TORTURE_TEST_RUNNABLE config RCU_CPU_STALL_TIMEOUT int "RCU CPU stall timeout in seconds" - depends on TREE_RCU || TREE_PREEMPT_RCU + depends on RCU_STALL_COMMON range 3 300 default 21 help @@ -1008,6 +1010,7 @@ config RCU_CPU_STALL_INFO config RCU_TRACE bool "Enable tracing for RCU" depends on DEBUG_KERNEL + select TRACE_CLOCK help This option provides tracing in RCU which presents stats in debugfs for debugging RCU implementation. @@ -1015,6 +1018,8 @@ config RCU_TRACE Say Y here if you want to enable RCU tracing Say N if you are unsure. +endmenu # "RCU Debugging" + config KPROBES_SANITY_TEST bool "Kprobes sanity tests" depends on DEBUG_KERNEL |