diff options
Diffstat (limited to 'kernel/rcutree_plugin.h')
-rw-r--r-- | kernel/rcutree_plugin.h | 460 |
1 files changed, 440 insertions, 20 deletions
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 769e12e3151b..130c97b027f2 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -28,7 +28,7 @@ #include <linux/gfp.h> #include <linux/oom.h> #include <linux/smpboot.h> -#include <linux/tick.h> +#include "time/tick-internal.h" #define RCU_KTHREAD_PRIO 1 @@ -110,9 +110,7 @@ static void __init rcu_bootup_announce_oddness(void) #ifdef CONFIG_TREE_PREEMPT_RCU -struct rcu_state rcu_preempt_state = - RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu); -DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data); +RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu); static struct rcu_state *rcu_state = &rcu_preempt_state; static int rcu_preempted_readers_exp(struct rcu_node *rnp); @@ -169,7 +167,7 @@ static void rcu_preempt_qs(int cpu) struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu); if (rdp->passed_quiesce == 0) - trace_rcu_grace_period("rcu_preempt", rdp->gpnum, "cpuqs"); + trace_rcu_grace_period(TPS("rcu_preempt"), rdp->gpnum, TPS("cpuqs")); rdp->passed_quiesce = 1; current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; } @@ -388,7 +386,7 @@ void rcu_read_unlock_special(struct task_struct *t) np = rcu_next_node_entry(t, rnp); list_del_init(&t->rcu_node_entry); t->rcu_blocked_node = NULL; - trace_rcu_unlock_preempted_task("rcu_preempt", + trace_rcu_unlock_preempted_task(TPS("rcu_preempt"), rnp->gpnum, t->pid); if (&t->rcu_node_entry == rnp->gp_tasks) rnp->gp_tasks = np; @@ -412,7 +410,7 @@ void rcu_read_unlock_special(struct task_struct *t) */ empty_exp_now = !rcu_preempted_readers_exp(rnp); if (!empty && !rcu_preempt_blocked_readers_cgp(rnp)) { - trace_rcu_quiescent_state_report("preempt_rcu", + trace_rcu_quiescent_state_report(TPS("preempt_rcu"), rnp->gpnum, 0, rnp->qsmask, rnp->level, @@ -1250,12 +1248,12 @@ static int rcu_boost_kthread(void *arg) int spincnt = 0; int more2boost; - trace_rcu_utilization("Start boost kthread@init"); + trace_rcu_utilization(TPS("Start boost kthread@init")); for (;;) { rnp->boost_kthread_status = RCU_KTHREAD_WAITING; - trace_rcu_utilization("End boost kthread@rcu_wait"); + trace_rcu_utilization(TPS("End boost kthread@rcu_wait")); rcu_wait(rnp->boost_tasks || rnp->exp_tasks); - trace_rcu_utilization("Start boost kthread@rcu_wait"); + trace_rcu_utilization(TPS("Start boost kthread@rcu_wait")); rnp->boost_kthread_status = RCU_KTHREAD_RUNNING; more2boost = rcu_boost(rnp); if (more2boost) @@ -1264,14 +1262,14 @@ static int rcu_boost_kthread(void *arg) spincnt = 0; if (spincnt > 10) { rnp->boost_kthread_status = RCU_KTHREAD_YIELDING; - trace_rcu_utilization("End boost kthread@rcu_yield"); + trace_rcu_utilization(TPS("End boost kthread@rcu_yield")); schedule_timeout_interruptible(2); - trace_rcu_utilization("Start boost kthread@rcu_yield"); + trace_rcu_utilization(TPS("Start boost kthread@rcu_yield")); spincnt = 0; } } /* NOTREACHED */ - trace_rcu_utilization("End boost kthread@notreached"); + trace_rcu_utilization(TPS("End boost kthread@notreached")); return 0; } @@ -1419,7 +1417,7 @@ static void rcu_cpu_kthread(unsigned int cpu) int spincnt; for (spincnt = 0; spincnt < 10; spincnt++) { - trace_rcu_utilization("Start CPU kthread@rcu_wait"); + trace_rcu_utilization(TPS("Start CPU kthread@rcu_wait")); local_bh_disable(); *statusp = RCU_KTHREAD_RUNNING; this_cpu_inc(rcu_cpu_kthread_loops); @@ -1431,15 +1429,15 @@ static void rcu_cpu_kthread(unsigned int cpu) rcu_kthread_do_work(); local_bh_enable(); if (*workp == 0) { - trace_rcu_utilization("End CPU kthread@rcu_wait"); + trace_rcu_utilization(TPS("End CPU kthread@rcu_wait")); *statusp = RCU_KTHREAD_WAITING; return; } } *statusp = RCU_KTHREAD_YIELDING; - trace_rcu_utilization("Start CPU kthread@rcu_yield"); + trace_rcu_utilization(TPS("Start CPU kthread@rcu_yield")); schedule_timeout_interruptible(2); - trace_rcu_utilization("End CPU kthread@rcu_yield"); + trace_rcu_utilization(TPS("End CPU kthread@rcu_yield")); *statusp = RCU_KTHREAD_WAITING; } @@ -2202,7 +2200,7 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp) * Wait for the grace period. Do so interruptibly to avoid messing * up the load average. */ - trace_rcu_future_gp(rnp, rdp, c, "StartWait"); + trace_rcu_future_gp(rnp, rdp, c, TPS("StartWait")); for (;;) { wait_event_interruptible( rnp->nocb_gp_wq[c & 0x1], @@ -2210,9 +2208,9 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp) if (likely(d)) break; flush_signals(current); - trace_rcu_future_gp(rnp, rdp, c, "ResumeWait"); + trace_rcu_future_gp(rnp, rdp, c, TPS("ResumeWait")); } - trace_rcu_future_gp(rnp, rdp, c, "EndWait"); + trace_rcu_future_gp(rnp, rdp, c, TPS("EndWait")); smp_mb(); /* Ensure that CB invocation happens after GP end. */ } @@ -2375,3 +2373,425 @@ static void rcu_kick_nohz_cpu(int cpu) smp_send_reschedule(cpu); #endif /* #ifdef CONFIG_NO_HZ_FULL */ } + + +#ifdef CONFIG_NO_HZ_FULL_SYSIDLE + +/* + * Define RCU flavor that holds sysidle state. This needs to be the + * most active flavor of RCU. + */ +#ifdef CONFIG_PREEMPT_RCU +static struct rcu_state *rcu_sysidle_state = &rcu_preempt_state; +#else /* #ifdef CONFIG_PREEMPT_RCU */ +static struct rcu_state *rcu_sysidle_state = &rcu_sched_state; +#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ + +static int full_sysidle_state; /* Current system-idle state. */ +#define RCU_SYSIDLE_NOT 0 /* Some CPU is not idle. */ +#define RCU_SYSIDLE_SHORT 1 /* All CPUs idle for brief period. */ +#define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ +#define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ +#define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle state. */ + +/* + * Invoked to note exit from irq or task transition to idle. Note that + * usermode execution does -not- count as idle here! After all, we want + * to detect full-system idle states, not RCU quiescent states and grace + * periods. The caller must have disabled interrupts. + */ +static void rcu_sysidle_enter(struct rcu_dynticks *rdtp, int irq) +{ + unsigned long j; + + /* Adjust nesting, check for fully idle. */ + if (irq) { + rdtp->dynticks_idle_nesting--; + WARN_ON_ONCE(rdtp->dynticks_idle_nesting < 0); + if (rdtp->dynticks_idle_nesting != 0) + return; /* Still not fully idle. */ + } else { + if ((rdtp->dynticks_idle_nesting & DYNTICK_TASK_NEST_MASK) == + DYNTICK_TASK_NEST_VALUE) { + rdtp->dynticks_idle_nesting = 0; + } else { + rdtp->dynticks_idle_nesting -= DYNTICK_TASK_NEST_VALUE; + WARN_ON_ONCE(rdtp->dynticks_idle_nesting < 0); + return; /* Still not fully idle. */ + } + } + + /* Record start of fully idle period. */ + j = jiffies; + ACCESS_ONCE(rdtp->dynticks_idle_jiffies) = j; + smp_mb__before_atomic_inc(); + atomic_inc(&rdtp->dynticks_idle); + smp_mb__after_atomic_inc(); + WARN_ON_ONCE(atomic_read(&rdtp->dynticks_idle) & 0x1); +} + +/* + * Unconditionally force exit from full system-idle state. This is + * invoked when a normal CPU exits idle, but must be called separately + * for the timekeeping CPU (tick_do_timer_cpu). The reason for this + * is that the timekeeping CPU is permitted to take scheduling-clock + * interrupts while the system is in system-idle state, and of course + * rcu_sysidle_exit() has no way of distinguishing a scheduling-clock + * interrupt from any other type of interrupt. + */ +void rcu_sysidle_force_exit(void) +{ + int oldstate = ACCESS_ONCE(full_sysidle_state); + int newoldstate; + + /* + * Each pass through the following loop attempts to exit full + * system-idle state. If contention proves to be a problem, + * a trylock-based contention tree could be used here. + */ + while (oldstate > RCU_SYSIDLE_SHORT) { + newoldstate = cmpxchg(&full_sysidle_state, + oldstate, RCU_SYSIDLE_NOT); + if (oldstate == newoldstate && + oldstate == RCU_SYSIDLE_FULL_NOTED) { + rcu_kick_nohz_cpu(tick_do_timer_cpu); + return; /* We cleared it, done! */ + } + oldstate = newoldstate; + } + smp_mb(); /* Order initial oldstate fetch vs. later non-idle work. */ +} + +/* + * Invoked to note entry to irq or task transition from idle. Note that + * usermode execution does -not- count as idle here! The caller must + * have disabled interrupts. + */ +static void rcu_sysidle_exit(struct rcu_dynticks *rdtp, int irq) +{ + /* Adjust nesting, check for already non-idle. */ + if (irq) { + rdtp->dynticks_idle_nesting++; + WARN_ON_ONCE(rdtp->dynticks_idle_nesting <= 0); + if (rdtp->dynticks_idle_nesting != 1) + return; /* Already non-idle. */ + } else { + /* + * Allow for irq misnesting. Yes, it really is possible + * to enter an irq handler then never leave it, and maybe + * also vice versa. Handle both possibilities. + */ + if (rdtp->dynticks_idle_nesting & DYNTICK_TASK_NEST_MASK) { + rdtp->dynticks_idle_nesting += DYNTICK_TASK_NEST_VALUE; + WARN_ON_ONCE(rdtp->dynticks_idle_nesting <= 0); + return; /* Already non-idle. */ + } else { + rdtp->dynticks_idle_nesting = DYNTICK_TASK_EXIT_IDLE; + } + } + + /* Record end of idle period. */ + smp_mb__before_atomic_inc(); + atomic_inc(&rdtp->dynticks_idle); + smp_mb__after_atomic_inc(); + WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks_idle) & 0x1)); + + /* + * If we are the timekeeping CPU, we are permitted to be non-idle + * during a system-idle state. This must be the case, because + * the timekeeping CPU has to take scheduling-clock interrupts + * during the time that the system is transitioning to full + * system-idle state. This means that the timekeeping CPU must + * invoke rcu_sysidle_force_exit() directly if it does anything + * more than take a scheduling-clock interrupt. + */ + if (smp_processor_id() == tick_do_timer_cpu) + return; + + /* Update system-idle state: We are clearly no longer fully idle! */ + rcu_sysidle_force_exit(); +} + +/* + * Check to see if the current CPU is idle. Note that usermode execution + * does not count as idle. The caller must have disabled interrupts. + */ +static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, + unsigned long *maxj) +{ + int cur; + unsigned long j; + struct rcu_dynticks *rdtp = rdp->dynticks; + + /* + * If some other CPU has already reported non-idle, if this is + * not the flavor of RCU that tracks sysidle state, or if this + * is an offline or the timekeeping CPU, nothing to do. + */ + if (!*isidle || rdp->rsp != rcu_sysidle_state || + cpu_is_offline(rdp->cpu) || rdp->cpu == tick_do_timer_cpu) + return; + if (rcu_gp_in_progress(rdp->rsp)) + WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu); + + /* Pick up current idle and NMI-nesting counter and check. */ + cur = atomic_read(&rdtp->dynticks_idle); + if (cur & 0x1) { + *isidle = false; /* We are not idle! */ + return; + } + smp_mb(); /* Read counters before timestamps. */ + + /* Pick up timestamps. */ + j = ACCESS_ONCE(rdtp->dynticks_idle_jiffies); + /* If this CPU entered idle more recently, update maxj timestamp. */ + if (ULONG_CMP_LT(*maxj, j)) + *maxj = j; +} + +/* + * Is this the flavor of RCU that is handling full-system idle? + */ +static bool is_sysidle_rcu_state(struct rcu_state *rsp) +{ + return rsp == rcu_sysidle_state; +} + +/* + * Bind the grace-period kthread for the sysidle flavor of RCU to the + * timekeeping CPU. + */ +static void rcu_bind_gp_kthread(void) +{ + int cpu = ACCESS_ONCE(tick_do_timer_cpu); + + if (cpu < 0 || cpu >= nr_cpu_ids) + return; + if (raw_smp_processor_id() != cpu) + set_cpus_allowed_ptr(current, cpumask_of(cpu)); +} + +/* + * Return a delay in jiffies based on the number of CPUs, rcu_node + * leaf fanout, and jiffies tick rate. The idea is to allow larger + * systems more time to transition to full-idle state in order to + * avoid the cache thrashing that otherwise occur on the state variable. + * Really small systems (less than a couple of tens of CPUs) should + * instead use a single global atomically incremented counter, and later + * versions of this will automatically reconfigure themselves accordingly. + */ +static unsigned long rcu_sysidle_delay(void) +{ + if (nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) + return 0; + return DIV_ROUND_UP(nr_cpu_ids * HZ, rcu_fanout_leaf * 1000); +} + +/* + * Advance the full-system-idle state. This is invoked when all of + * the non-timekeeping CPUs are idle. + */ +static void rcu_sysidle(unsigned long j) +{ + /* Check the current state. */ + switch (ACCESS_ONCE(full_sysidle_state)) { + case RCU_SYSIDLE_NOT: + + /* First time all are idle, so note a short idle period. */ + ACCESS_ONCE(full_sysidle_state) = RCU_SYSIDLE_SHORT; + break; + + case RCU_SYSIDLE_SHORT: + + /* + * Idle for a bit, time to advance to next state? + * cmpxchg failure means race with non-idle, let them win. + */ + if (ULONG_CMP_GE(jiffies, j + rcu_sysidle_delay())) + (void)cmpxchg(&full_sysidle_state, + RCU_SYSIDLE_SHORT, RCU_SYSIDLE_LONG); + break; + + case RCU_SYSIDLE_LONG: + + /* + * Do an additional check pass before advancing to full. + * cmpxchg failure means race with non-idle, let them win. + */ + if (ULONG_CMP_GE(jiffies, j + rcu_sysidle_delay())) + (void)cmpxchg(&full_sysidle_state, + RCU_SYSIDLE_LONG, RCU_SYSIDLE_FULL); + break; + + default: + break; + } +} + +/* + * Found a non-idle non-timekeeping CPU, so kick the system-idle state + * back to the beginning. + */ +static void rcu_sysidle_cancel(void) +{ + smp_mb(); + ACCESS_ONCE(full_sysidle_state) = RCU_SYSIDLE_NOT; +} + +/* + * Update the sysidle state based on the results of a force-quiescent-state + * scan of the CPUs' dyntick-idle state. + */ +static void rcu_sysidle_report(struct rcu_state *rsp, int isidle, + unsigned long maxj, bool gpkt) +{ + if (rsp != rcu_sysidle_state) + return; /* Wrong flavor, ignore. */ + if (gpkt && nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) + return; /* Running state machine from timekeeping CPU. */ + if (isidle) + rcu_sysidle(maxj); /* More idle! */ + else + rcu_sysidle_cancel(); /* Idle is over. */ +} + +/* + * Wrapper for rcu_sysidle_report() when called from the grace-period + * kthread's context. + */ +static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, + unsigned long maxj) +{ + rcu_sysidle_report(rsp, isidle, maxj, true); +} + +/* Callback and function for forcing an RCU grace period. */ +struct rcu_sysidle_head { + struct rcu_head rh; + int inuse; +}; + +static void rcu_sysidle_cb(struct rcu_head *rhp) +{ + struct rcu_sysidle_head *rshp; + + /* + * The following memory barrier is needed to replace the + * memory barriers that would normally be in the memory + * allocator. + */ + smp_mb(); /* grace period precedes setting inuse. */ + + rshp = container_of(rhp, struct rcu_sysidle_head, rh); + ACCESS_ONCE(rshp->inuse) = 0; +} + +/* + * Check to see if the system is fully idle, other than the timekeeping CPU. + * The caller must have disabled interrupts. + */ +bool rcu_sys_is_idle(void) +{ + static struct rcu_sysidle_head rsh; + int rss = ACCESS_ONCE(full_sysidle_state); + + if (WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu)) + return false; + + /* Handle small-system case by doing a full scan of CPUs. */ + if (nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) { + int oldrss = rss - 1; + + /* + * One pass to advance to each state up to _FULL. + * Give up if any pass fails to advance the state. + */ + while (rss < RCU_SYSIDLE_FULL && oldrss < rss) { + int cpu; + bool isidle = true; + unsigned long maxj = jiffies - ULONG_MAX / 4; + struct rcu_data *rdp; + + /* Scan all the CPUs looking for nonidle CPUs. */ + for_each_possible_cpu(cpu) { + rdp = per_cpu_ptr(rcu_sysidle_state->rda, cpu); + rcu_sysidle_check_cpu(rdp, &isidle, &maxj); + if (!isidle) + break; + } + rcu_sysidle_report(rcu_sysidle_state, + isidle, maxj, false); + oldrss = rss; + rss = ACCESS_ONCE(full_sysidle_state); + } + } + + /* If this is the first observation of an idle period, record it. */ + if (rss == RCU_SYSIDLE_FULL) { + rss = cmpxchg(&full_sysidle_state, + RCU_SYSIDLE_FULL, RCU_SYSIDLE_FULL_NOTED); + return rss == RCU_SYSIDLE_FULL; + } + + smp_mb(); /* ensure rss load happens before later caller actions. */ + + /* If already fully idle, tell the caller (in case of races). */ + if (rss == RCU_SYSIDLE_FULL_NOTED) + return true; + + /* + * If we aren't there yet, and a grace period is not in flight, + * initiate a grace period. Either way, tell the caller that + * we are not there yet. We use an xchg() rather than an assignment + * to make up for the memory barriers that would otherwise be + * provided by the memory allocator. + */ + if (nr_cpu_ids > CONFIG_NO_HZ_FULL_SYSIDLE_SMALL && + !rcu_gp_in_progress(rcu_sysidle_state) && + !rsh.inuse && xchg(&rsh.inuse, 1) == 0) + call_rcu(&rsh.rh, rcu_sysidle_cb); + return false; +} + +/* + * Initialize dynticks sysidle state for CPUs coming online. + */ +static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp) +{ + rdtp->dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE; +} + +#else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ + +static void rcu_sysidle_enter(struct rcu_dynticks *rdtp, int irq) +{ +} + +static void rcu_sysidle_exit(struct rcu_dynticks *rdtp, int irq) +{ +} + +static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, + unsigned long *maxj) +{ +} + +static bool is_sysidle_rcu_state(struct rcu_state *rsp) +{ + return false; +} + +static void rcu_bind_gp_kthread(void) +{ +} + +static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, + unsigned long maxj) +{ +} + +static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp) +{ +} + +#endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ |