diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/cpu.c | 1 | ||||
| -rw-r--r-- | kernel/debug/kdb/kdb_support.c | 2 | ||||
| -rw-r--r-- | kernel/events/core.c | 2 | ||||
| -rw-r--r-- | kernel/lockdep.c | 22 | ||||
| -rw-r--r-- | kernel/rcu.h | 7 | ||||
| -rw-r--r-- | kernel/rcupdate.c | 12 | ||||
| -rw-r--r-- | kernel/rcutiny.c | 149 | ||||
| -rw-r--r-- | kernel/rcutiny_plugin.h | 29 | ||||
| -rw-r--r-- | kernel/rcutorture.c | 225 | ||||
| -rw-r--r-- | kernel/rcutree.c | 290 | ||||
| -rw-r--r-- | kernel/rcutree.h | 26 | ||||
| -rw-r--r-- | kernel/rcutree_plugin.h | 289 | ||||
| -rw-r--r-- | kernel/rcutree_trace.c | 12 | ||||
| -rw-r--r-- | kernel/rtmutex.c | 8 | ||||
| -rw-r--r-- | kernel/softirq.c | 4 | ||||
| -rw-r--r-- | kernel/time/tick-sched.c | 97 | ||||
| -rw-r--r-- | kernel/trace/trace.c | 1 |
17 files changed, 933 insertions, 243 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c index 563f13609470..9d448ddb2247 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -380,6 +380,7 @@ out: cpu_maps_update_done(); return err; } +EXPORT_SYMBOL_GPL(cpu_up); #ifdef CONFIG_PM_SLEEP_SMP static cpumask_var_t frozen_cpus; diff --git a/kernel/debug/kdb/kdb_support.c b/kernel/debug/kdb/kdb_support.c index 5532dd37aa86..7d6fb40d2188 100644 --- a/kernel/debug/kdb/kdb_support.c +++ b/kernel/debug/kdb/kdb_support.c @@ -636,7 +636,7 @@ char kdb_task_state_char (const struct task_struct *p) (p->exit_state & EXIT_ZOMBIE) ? 'Z' : (p->exit_state & EXIT_DEAD) ? 'E' : (p->state & TASK_INTERRUPTIBLE) ? 'S' : '?'; - if (p->pid == 0) { + if (is_idle_task(p)) { /* Idle task. Is it really idle, apart from the kdb * interrupt? */ if (!kdb_task_has_cpu(p) || kgdb_info[cpu].irq_depth == 1) { diff --git a/kernel/events/core.c b/kernel/events/core.c index 58690af323e4..fc0e7ff11dda 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5366,7 +5366,7 @@ static enum hrtimer_restart perf_swevent_hrtimer(struct hrtimer *hrtimer) regs = get_irq_regs(); if (regs && !perf_exclude_event(event, regs)) { - if (!(event->attr.exclude_idle && current->pid == 0)) + if (!(event->attr.exclude_idle && is_idle_task(current))) if (perf_event_overflow(event, &data, regs)) ret = HRTIMER_NORESTART; } diff --git a/kernel/lockdep.c b/kernel/lockdep.c index e69d633d6aa6..8fb755132322 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -4181,6 +4181,28 @@ void lockdep_rcu_suspicious(const char *file, const int line, const char *s) printk("%s:%d %s!\n", file, line, s); printk("\nother info that might help us debug this:\n\n"); printk("\nrcu_scheduler_active = %d, debug_locks = %d\n", rcu_scheduler_active, debug_locks); + + /* + * If a CPU is in the RCU-free window in idle (ie: in the section + * between rcu_idle_enter() and rcu_idle_exit(), then RCU + * considers that CPU to be in an "extended quiescent state", + * which means that RCU will be completely ignoring that CPU. + * Therefore, rcu_read_lock() and friends have absolutely no + * effect on a CPU running in that state. In other words, even if + * such an RCU-idle CPU has called rcu_read_lock(), RCU might well + * delete data structures out from under it. RCU really has no + * choice here: 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. + * + * So complain bitterly if someone does call rcu_read_lock(), + * rcu_read_lock_bh() and so on from extended quiescent states. + */ + if (rcu_is_cpu_idle()) + printk("RCU used illegally from extended quiescent state!\n"); + lockdep_print_held_locks(curr); printk("\nstack backtrace:\n"); dump_stack(); diff --git a/kernel/rcu.h b/kernel/rcu.h index f600868d550d..aa88baab5f78 100644 --- a/kernel/rcu.h +++ b/kernel/rcu.h @@ -30,6 +30,13 @@ #endif /* #else #ifdef CONFIG_RCU_TRACE */ /* + * Process-level increment to ->dynticks_nesting field. This allows for + * architectures that use half-interrupts and half-exceptions from + * process context. + */ +#define DYNTICK_TASK_NESTING (LLONG_MAX / 2 - 1) + +/* * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally * by call_rcu() and rcu callback execution, and are therefore not part of the * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors. diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index c5b98e565aee..2bc4e135ff23 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -93,6 +93,8 @@ int rcu_read_lock_bh_held(void) { if (!debug_lockdep_rcu_enabled()) return 1; + if (rcu_is_cpu_idle()) + return 0; return in_softirq() || irqs_disabled(); } EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held); @@ -316,3 +318,13 @@ struct debug_obj_descr rcuhead_debug_descr = { }; 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) +{ + trace_rcu_torture_read(rcutorturename, rhp); +} +EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read); +#else +#define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0) +#endif diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c index 636af6d9c6e5..977296dca0a4 100644 --- a/kernel/rcutiny.c +++ b/kernel/rcutiny.c @@ -53,31 +53,137 @@ static void __call_rcu(struct rcu_head *head, #include "rcutiny_plugin.h" -#ifdef CONFIG_NO_HZ +static long long rcu_dynticks_nesting = DYNTICK_TASK_NESTING; -static long rcu_dynticks_nesting = 1; +/* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */ +static void rcu_idle_enter_common(long long oldval) +{ + if (rcu_dynticks_nesting) { + RCU_TRACE(trace_rcu_dyntick("--=", + oldval, rcu_dynticks_nesting)); + return; + } + RCU_TRACE(trace_rcu_dyntick("Start", oldval, rcu_dynticks_nesting)); + if (!is_idle_task(current)) { + struct task_struct *idle = idle_task(smp_processor_id()); + + RCU_TRACE(trace_rcu_dyntick("Error on entry: not idle task", + oldval, rcu_dynticks_nesting)); + ftrace_dump(DUMP_ALL); + 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_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */ +} /* - * Enter dynticks-idle mode, which is an extended quiescent state - * if we have fully entered that mode (i.e., if the new value of - * dynticks_nesting is zero). + * Enter idle, which is an extended quiescent state if we have fully + * entered that mode (i.e., if the new value of dynticks_nesting is zero). */ -void rcu_enter_nohz(void) +void rcu_idle_enter(void) { - if (--rcu_dynticks_nesting == 0) - rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */ + unsigned long flags; + long long oldval; + + local_irq_save(flags); + oldval = rcu_dynticks_nesting; + rcu_dynticks_nesting = 0; + rcu_idle_enter_common(oldval); + local_irq_restore(flags); } /* - * Exit dynticks-idle mode, so that we are no longer in an extended - * quiescent state. + * Exit an interrupt handler towards idle. */ -void rcu_exit_nohz(void) +void rcu_irq_exit(void) +{ + unsigned long flags; + long long oldval; + + local_irq_save(flags); + oldval = rcu_dynticks_nesting; + rcu_dynticks_nesting--; + WARN_ON_ONCE(rcu_dynticks_nesting < 0); + rcu_idle_enter_common(oldval); + local_irq_restore(flags); +} + +/* Common code for rcu_idle_exit() and rcu_irq_enter(), see kernel/rcutree.c. */ +static void rcu_idle_exit_common(long long oldval) { + if (oldval) { + RCU_TRACE(trace_rcu_dyntick("++=", + oldval, rcu_dynticks_nesting)); + return; + } + RCU_TRACE(trace_rcu_dyntick("End", oldval, rcu_dynticks_nesting)); + if (!is_idle_task(current)) { + struct task_struct *idle = idle_task(smp_processor_id()); + + RCU_TRACE(trace_rcu_dyntick("Error on exit: not idle task", + oldval, rcu_dynticks_nesting)); + ftrace_dump(DUMP_ALL); + 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 idle, so that we are no longer in an extended quiescent state. + */ +void rcu_idle_exit(void) +{ + unsigned long flags; + long long oldval; + + local_irq_save(flags); + oldval = rcu_dynticks_nesting; + WARN_ON_ONCE(oldval != 0); + rcu_dynticks_nesting = DYNTICK_TASK_NESTING; + rcu_idle_exit_common(oldval); + local_irq_restore(flags); +} + +/* + * Enter an interrupt handler, moving away from idle. + */ +void rcu_irq_enter(void) +{ + unsigned long flags; + long long oldval; + + local_irq_save(flags); + oldval = rcu_dynticks_nesting; rcu_dynticks_nesting++; + WARN_ON_ONCE(rcu_dynticks_nesting == 0); + rcu_idle_exit_common(oldval); + local_irq_restore(flags); +} + +#ifdef CONFIG_PROVE_RCU + +/* + * Test whether RCU thinks that the current CPU is idle. + */ +int rcu_is_cpu_idle(void) +{ + return !rcu_dynticks_nesting; } +EXPORT_SYMBOL(rcu_is_cpu_idle); + +#endif /* #ifdef CONFIG_PROVE_RCU */ -#endif /* #ifdef CONFIG_NO_HZ */ +/* + * Test whether the current CPU was interrupted from idle. Nested + * interrupts don't count, we must be running at the first interrupt + * level. + */ +int rcu_is_cpu_rrupt_from_idle(void) +{ + return rcu_dynticks_nesting <= 0; +} /* * Helper function for rcu_sched_qs() and rcu_bh_qs(). @@ -126,14 +232,13 @@ void rcu_bh_qs(int cpu) /* * Check to see if the scheduling-clock interrupt came from an extended - * quiescent state, and, if so, tell RCU about it. + * quiescent state, and, if so, tell RCU about it. This function must + * be called from hardirq context. It is normally called from the + * scheduling-clock interrupt. */ void rcu_check_callbacks(int cpu, int user) { - if (user || - (idle_cpu(cpu) && - !in_softirq() && - hardirq_count() <= (1 << HARDIRQ_SHIFT))) + if (user || rcu_is_cpu_rrupt_from_idle()) rcu_sched_qs(cpu); else if (!in_softirq()) rcu_bh_qs(cpu); @@ -154,7 +259,11 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) /* If no RCU callbacks ready to invoke, just return. */ if (&rcp->rcucblist == rcp->donetail) { RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, -1)); - RCU_TRACE(trace_rcu_batch_end(rcp->name, 0)); + RCU_TRACE(trace_rcu_batch_end(rcp->name, 0, + ACCESS_ONCE(rcp->rcucblist), + need_resched(), + is_idle_task(current), + rcu_is_callbacks_kthread())); return; } @@ -183,7 +292,9 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) RCU_TRACE(cb_count++); } RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count)); - RCU_TRACE(trace_rcu_batch_end(rcp->name, cb_count)); + RCU_TRACE(trace_rcu_batch_end(rcp->name, cb_count, 0, need_resched(), + is_idle_task(current), + rcu_is_callbacks_kthread())); } static void rcu_process_callbacks(struct softirq_action *unused) diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h index 2b0484a5dc28..9cb1ae4aabdd 100644 --- a/kernel/rcutiny_plugin.h +++ b/kernel/rcutiny_plugin.h @@ -312,8 +312,8 @@ static int rcu_boost(void) rt_mutex_lock(&mtx); rt_mutex_unlock(&mtx); /* Keep lockdep happy. */ - return rcu_preempt_ctrlblk.boost_tasks != NULL || - rcu_preempt_ctrlblk.exp_tasks != NULL; + return ACCESS_ONCE(rcu_preempt_ctrlblk.boost_tasks) != NULL || + ACCESS_ONCE(rcu_preempt_ctrlblk.exp_tasks) != NULL; } /* @@ -885,6 +885,19 @@ static void invoke_rcu_callbacks(void) wake_up(&rcu_kthread_wq); } +#ifdef CONFIG_RCU_TRACE + +/* + * Is the current CPU running the RCU-callbacks kthread? + * Caller must have preemption disabled. + */ +static bool rcu_is_callbacks_kthread(void) +{ + return rcu_kthread_task == current; +} + +#endif /* #ifdef CONFIG_RCU_TRACE */ + /* * This kthread invokes RCU callbacks whose grace periods have * elapsed. It is awakened as needed, and takes the place of the @@ -938,6 +951,18 @@ void invoke_rcu_callbacks(void) raise_softirq(RCU_SOFTIRQ); } +#ifdef CONFIG_RCU_TRACE + +/* + * There is no callback kthread, so this thread is never it. + */ +static bool rcu_is_callbacks_kthread(void) +{ + return false; +} + +#endif /* #ifdef CONFIG_RCU_TRACE */ + void rcu_init(void) { open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c index 764825c2685c..88f17b8a3b1d 100644 --- a/kernel/rcutorture.c +++ b/kernel/rcutorture.c @@ -61,9 +61,11 @@ static int test_no_idle_hz; /* Test RCU's support for tickless idle CPUs. */ static int shuffle_interval = 3; /* Interval between shuffles (in sec)*/ static int stutter = 5; /* Start/stop testing interval (in sec) */ static int irqreader = 1; /* RCU readers from irq (timers). */ -static int fqs_duration = 0; /* Duration of bursts (us), 0 to disable. */ -static int fqs_holdoff = 0; /* Hold time within burst (us). */ +static int fqs_duration; /* Duration of bursts (us), 0 to disable. */ +static int fqs_holdoff; /* Hold time within burst (us). */ static int fqs_stutter = 3; /* Wait time between bursts (s). */ +static int onoff_interval; /* Wait time between CPU hotplugs, 0=disable. */ +static int shutdown_secs; /* Shutdown time (s). <=0 for no shutdown. */ static int test_boost = 1; /* Test RCU prio boost: 0=no, 1=maybe, 2=yes. */ static int test_boost_interval = 7; /* Interval between boost tests, seconds. */ static int test_boost_duration = 4; /* Duration of each boost test, seconds. */ @@ -91,6 +93,10 @@ module_param(fqs_holdoff, int, 0444); MODULE_PARM_DESC(fqs_holdoff, "Holdoff time within fqs bursts (us)"); module_param(fqs_stutter, int, 0444); MODULE_PARM_DESC(fqs_stutter, "Wait time between fqs bursts (s)"); +module_param(onoff_interval, int, 0444); +MODULE_PARM_DESC(onoff_interval, "Time between CPU hotplugs (s), 0=disable"); +module_param(shutdown_secs, int, 0444); +MODULE_PARM_DESC(shutdown_secs, "Shutdown time (s), zero to disable."); module_param(test_boost, int, 0444); MODULE_PARM_DESC(test_boost, "Test RCU prio boost: 0=no, 1=maybe, 2=yes."); module_param(test_boost_interval, int, 0444); @@ -119,6 +125,10 @@ static struct task_struct *shuffler_task; static struct task_struct *stutter_task; static struct task_struct *fqs_task; static struct task_struct *boost_tasks[NR_CPUS]; +static struct task_struct *shutdown_task; +#ifdef CONFIG_HOTPLUG_CPU +static struct task_struct *onoff_task; +#endif /* #ifdef CONFIG_HOTPLUG_CPU */ #define RCU_TORTURE_PIPE_LEN 10 @@ -149,6 +159,10 @@ static long n_rcu_torture_boost_rterror; static long n_rcu_torture_boost_failure; static long n_rcu_torture_boosts; static long n_rcu_torture_timers; +static long n_offline_attempts; +static long n_offline_successes; +static long n_online_attempts; +static long n_online_successes; static struct list_head rcu_torture_removed; static cpumask_var_t shuffle_tmp_mask; @@ -160,6 +174,8 @@ static int stutter_pause_test; #define RCUTORTURE_RUNNABLE_INIT 0 #endif int rcutorture_runnable = RCUTORTURE_RUNNABLE_INIT; +module_param(rcutorture_runnable, int, 0444); +MODULE_PARM_DESC(rcutorture_runnable, "Start rcutorture at boot"); #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) #define rcu_can_boost() 1 @@ -167,6 +183,7 @@ int rcutorture_runnable = RCUTORTURE_RUNNABLE_INIT; #define rcu_can_boost() 0 #endif /* #else #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */ +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 */ /* and boost task create/destroy. */ @@ -182,6 +199,9 @@ static int fullstop = FULLSTOP_RMMOD; */ static DEFINE_MUTEX(fullstop_mutex); +/* Forward reference. */ +static void rcu_torture_cleanup(void); + /* * Detect and respond to a system shutdown. */ @@ -612,6 +632,30 @@ static struct rcu_torture_ops srcu_ops = { .name = "srcu" }; +static int srcu_torture_read_lock_raw(void) __acquires(&srcu_ctl) +{ + return srcu_read_lock_raw(&srcu_ctl); +} + +static void srcu_torture_read_unlock_raw(int idx) __releases(&srcu_ctl) +{ + srcu_read_unlock_raw(&srcu_ctl, idx); +} + +static struct rcu_torture_ops srcu_raw_ops = { + .init = srcu_torture_init, + .cleanup = srcu_torture_cleanup, + .readlock = srcu_torture_read_lock_raw, + .read_delay = srcu_read_delay, + .readunlock = srcu_torture_read_unlock_raw, + .completed = srcu_torture_completed, + .deferred_free = rcu_sync_torture_deferred_free, + .sync = srcu_torture_synchronize, + .cb_barrier = NULL, + .stats = srcu_torture_stats, + .name = "srcu_raw" +}; + static void srcu_torture_synchronize_expedited(void) { synchronize_srcu_expedited(&srcu_ctl); @@ -913,6 +957,18 @@ rcu_torture_fakewriter(void *arg) return 0; } +void rcutorture_trace_dump(void) +{ + static atomic_t beenhere = ATOMIC_INIT(0); + + if (atomic_read(&beenhere)) + return; + if (atomic_xchg(&beenhere, 1) != 0) + return; + do_trace_rcu_torture_read(cur_ops->name, (struct rcu_head *)~0UL); + ftrace_dump(DUMP_ALL); +} + /* * RCU torture reader from timer handler. Dereferences rcu_torture_current, * incrementing the corresponding element of the pipeline array. The @@ -934,6 +990,7 @@ static void rcu_torture_timer(unsigned long unused) rcu_read_lock_bh_held() || rcu_read_lock_sched_held() || srcu_read_lock_held(&srcu_ctl)); + do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu); if (p == NULL) { /* Leave because rcu_torture_writer is not yet underway */ cur_ops->readunlock(idx); @@ -951,6 +1008,8 @@ static void rcu_torture_timer(unsigned long unused) /* Should not happen, but... */ pipe_count = RCU_TORTURE_PIPE_LEN; } + if (pipe_count > 1) + rcutorture_trace_dump(); __this_cpu_inc(rcu_torture_count[pipe_count]); completed = cur_ops->completed() - completed; if (completed > RCU_TORTURE_PIPE_LEN) { @@ -994,6 +1053,7 @@ rcu_torture_reader(void *arg) rcu_read_lock_bh_held() || rcu_read_lock_sched_held() || srcu_read_lock_held(&srcu_ctl)); + do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu); if (p == NULL) { /* Wait for rcu_torture_writer to get underway */ cur_ops->readunlock(idx); @@ -1009,6 +1069,8 @@ rcu_torture_reader(void *arg) /* Should not happen, but... */ pipe_count = RCU_TORTURE_PIPE_LEN; } + if (pipe_count > 1) + rcutorture_trace_dump(); __this_cpu_inc(rcu_torture_count[pipe_count]); completed = cur_ops->completed() - completed; if (completed > RCU_TORTURE_PIPE_LEN) { @@ -1056,7 +1118,8 @@ rcu_torture_printk(char *page) cnt += sprintf(&page[cnt], "rtc: %p ver: %lu tfle: %d rta: %d rtaf: %d rtf: %d " "rtmbe: %d rtbke: %ld rtbre: %ld " - "rtbf: %ld rtb: %ld nt: %ld", + "rtbf: %ld rtb: %ld nt: %ld " + "onoff: %ld/%ld:%ld/%ld", rcu_torture_current, rcu_torture_current_version, list_empty(&rcu_torture_freelist), @@ -1068,7 +1131,11 @@ rcu_torture_printk(char *page) n_rcu_torture_boost_rterror, n_rcu_torture_boost_failure, n_rcu_torture_boosts, - n_rcu_torture_timers); + n_rcu_torture_timers, + n_online_successes, + n_online_attempts, + n_offline_successes, + n_offline_attempts); if (atomic_read(&n_rcu_torture_mberror) != 0 || n_rcu_torture_boost_ktrerror != 0 || n_rcu_torture_boost_rterror != 0 || @@ -1232,12 +1299,14 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, char *tag) "shuffle_interval=%d stutter=%d irqreader=%d " "fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d " "test_boost=%d/%d test_boost_interval=%d " - "test_boost_duration=%d\n", + "test_boost_duration=%d shutdown_secs=%d " + "onoff_interval=%d\n", torture_type, tag, nrealreaders, nfakewriters, stat_interval, verbose, test_no_idle_hz, shuffle_interval, stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter, test_boost, cur_ops->can_boost, - test_boost_interval, test_boost_duration); + test_boost_interval, test_boost_duration, shutdown_secs, + onoff_interval); } static struct notifier_block rcutorture_shutdown_nb = { @@ -1287,6 +1356,131 @@ static int rcutorture_booster_init(int cpu) return 0; } +/* + * Cause the rcutorture test to shutdown the system after the test has + * run for the time specified by the shutdown_secs module parameter. + */ +static int +rcu_torture_shutdown(void *arg) +{ + long delta; + unsigned long jiffies_snap; + + VERBOSE_PRINTK_STRING("rcu_torture_shutdown task started"); + jiffies_snap = ACCESS_ONCE(jiffies); + while (ULONG_CMP_LT(jiffies_snap, shutdown_time) && + !kthread_should_stop()) { + delta = shutdown_time - jiffies_snap; + if (verbose) + printk(KERN_ALERT "%s" TORTURE_FLAG + "rcu_torture_shutdown task: %lu " + "jiffies remaining\n", + torture_type, delta); + schedule_timeout_interruptible(delta); + jiffies_snap = ACCESS_ONCE(jiffies); + } + if (kthread_should_stop()) { + VERBOSE_PRINTK_STRING("rcu_torture_shutdown task stopping"); + return 0; + } + + /* OK, shut down the system. */ + + VERBOSE_PRINTK_STRING("rcu_torture_shutdown task shutting down system"); + shutdown_task = NULL; /* Avoid self-kill deadlock. */ + rcu_torture_cleanup(); /* Get the success/failure message. */ + kernel_power_off(); /* Shut down the system. */ + return 0; +} + +#ifdef CONFIG_HOTPLUG_CPU + +/* + * Execute random CPU-hotplug operations at the interval specified + * by the onoff_interval. + */ +static int +rcu_torture_onoff(void *arg) +{ + int cpu; + int maxcpu = -1; + DEFINE_RCU_RANDOM(rand); + + VERBOSE_PRINTK_STRING("rcu_torture_onoff task started"); + for_each_online_cpu(cpu) + maxcpu = cpu; + WARN_ON(maxcpu < 0); + while (!kthread_should_stop()) { + cpu = (rcu_random(&rand) >> 4) % (maxcpu + 1); + if (cpu_online(cpu) && cpu_is_hotpluggable(cpu)) { + if (verbose) + printk(KERN_ALERT "%s" TORTURE_FLAG + "rcu_torture_onoff task: offlining %d\n", + torture_type, cpu); + n_offline_attempts++; + if (cpu_down(cpu) == 0) { + if (verbose) + printk(KERN_ALERT "%s" TORTURE_FLAG + "rcu_torture_onoff task: " + "offlined %d\n", + torture_type, cpu); + n_offline_successes++; + } + } else if (cpu_is_hotpluggable(cpu)) { + if (verbose) + printk(KERN_ALERT "%s" TORTURE_FLAG + "rcu_torture_onoff task: onlining %d\n", + torture_type, cpu); + n_online_attempts++; + if (cpu_up(cpu) == 0) { + if (verbose) + printk(KERN_ALERT "%s" TORTURE_FLAG + "rcu_torture_onoff task: " + "onlined %d\n", + torture_type, cpu); + n_online_successes++; + } + } + schedule_timeout_interruptible(onoff_interval * HZ); + } + VERBOSE_PRINTK_STRING("rcu_torture_onoff task stopping"); + return 0; +} + +static int +rcu_torture_onoff_init(void) +{ + if (onoff_interval <= 0) + return 0; + onoff_task = kthread_run(rcu_torture_onoff, NULL, "rcu_torture_onoff"); + if (IS_ERR(onoff_task)) { + onoff_task = NULL; + return PTR_ERR(onoff_task); + } + return 0; +} + +static void rcu_torture_onoff_cleanup(void) +{ + if (onoff_task == NULL) + return; + VERBOSE_PRINTK_STRING("Stopping rcu_torture_onoff task"); + kthread_stop(onoff_task); +} + +#else /* #ifdef CONFIG_HOTPLUG_CPU */ + +static void +rcu_torture_onoff_init(void) +{ +} + +static void rcu_torture_onoff_cleanup(void) +{ +} + +#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ + static int rcutorture_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu) { @@ -1391,6 +1585,11 @@ rcu_torture_cleanup(void) for_each_possible_cpu(i) rcutorture_booster_cleanup(i); } + if (shutdown_task != NULL) { + VERBOSE_PRINTK_STRING("Stopping rcu_torture_shutdown task"); + kthread_stop(shutdown_task); + } + rcu_torture_onoff_cleanup(); /* Wait for all RCU callbacks to fire. */ @@ -1416,7 +1615,7 @@ rcu_torture_init(void) static struct rcu_torture_ops *torture_ops[] = { &rcu_ops, &rcu_sync_ops, &rcu_expedited_ops, &rcu_bh_ops, &rcu_bh_sync_ops, &rcu_bh_expedited_ops, - &srcu_ops, &srcu_expedited_ops, + &srcu_ops, &srcu_raw_ops, &srcu_expedited_ops, &sched_ops, &sched_sync_ops, &sched_expedited_ops, }; mutex_lock(&fullstop_mutex); @@ -1607,6 +1806,18 @@ rcu_torture_init(void) } } } + if (shutdown_secs > 0) { + shutdown_time = jiffies + shutdown_secs * HZ; + shutdown_task = kthread_run(rcu_torture_shutdown, NULL, + "rcu_torture_shutdown"); + if (IS_ERR(shutdown_task)) { + firsterr = PTR_ERR(shutdown_task); + VERBOSE_PRINTK_ERRSTRING("Failed to create shutdown"); + shutdown_task = NULL; + goto unwind; + } + } + rcu_torture_onoff_init(); register_reboot_notifier(&rcutorture_shutdown_nb); rcutorture_record_test_transition(); mutex_unlock(&fullstop_mutex); diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 6b76d812740c..6c4a6722abfd 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -69,7 +69,7 @@ static struct lock_class_key rcu_node_class[NUM_RCU_LVLS]; NUM_RCU_LVL_3, \ NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \ }, \ - .signaled = RCU_GP_IDLE, \ + .fqs_state = RCU_GP_IDLE, \ .gpnum = -300, \ .completed = -300, \ .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname##_state.onofflock), \ @@ -195,12 +195,10 @@ void rcu_note_context_switch(int cpu) } EXPORT_SYMBOL_GPL(rcu_note_context_switch); -#ifdef CONFIG_NO_HZ DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { - .dynticks_nesting = 1, + .dynticks_nesting = DYNTICK_TASK_NESTING, .dynticks = ATOMIC_INIT(1), }; -#endif /* #ifdef CONFIG_NO_HZ */ static int blimit = 10; /* Maximum callbacks per rcu_do_batch. */ static int qhimark = 10000; /* If this many pending, ignore blimit. */ @@ -328,11 +326,11 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp) return 1; } - /* If preemptible RCU, no point in sending reschedule IPI. */ - if (rdp->preemptible) - return 0; - - /* The CPU is online, so send it a reschedule IPI. */ + /* + * The CPU is online, so send it a reschedule IPI. This forces + * it through the scheduler, and (inefficiently) also handles cases + * where idle loops fail to inform RCU about the CPU being idle. + */ if (rdp->cpu != smp_processor_id()) smp_send_reschedule(rdp->cpu); else @@ -343,59 +341,181 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp) #endif /* #ifdef CONFIG_SMP */ -#ifdef CONFIG_NO_HZ +/* + * rcu_idle_enter_common - inform RCU that current CPU is moving towards idle + * + * 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_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval) +{ + trace_rcu_dyntick("Start", oldval, 0); + if (!is_idle_task(current)) { + struct task_struct *idle = idle_task(smp_processor_id()); + + trace_rcu_dyntick("Error on entry: not idle task", oldval, 0); + ftrace_dump(DUMP_ALL); + 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); +} /** - * rcu_enter_nohz - inform RCU that current CPU is entering nohz + * rcu_idle_enter - inform RCU that current CPU is entering idle * - * Enter nohz mode, in other words, -leave- the mode in which RCU + * 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 nohz mode, a possibility - * handled by rcu_irq_enter() and rcu_irq_exit()). + * 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_enter_nohz(void) +void rcu_idle_enter(void) { unsigned long flags; + long long oldval; struct rcu_dynticks *rdtp; local_irq_save(flags); rdtp = &__get_cpu_var(rcu_dynticks); - if (--rdtp->dynticks_nesting) { - local_irq_restore(flags); - return; - } - trace_rcu_dyntick("Start"); - /* 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); + oldval = rdtp->dynticks_nesting; + rdtp->dynticks_nesting = 0; + rcu_idle_enter_common(rdtp, oldval); local_irq_restore(flags); } -/* - * rcu_exit_nohz - inform RCU that current CPU is leaving nohz +/** + * 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. * - * Exit nohz mode, in other words, -enter- the mode in which RCU - * read-side critical sections normally 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_exit_nohz(void) +void rcu_irq_exit(void) { unsigned long flags; + long long oldval; struct rcu_dynticks *rdtp; local_irq_save(flags); rdtp = &__get_cpu_var(rcu_dynticks); - if (rdtp->dynticks_nesting++) { - local_irq_restore(flags); - return; - } + oldval = rdtp->dynticks_nesting; + rdtp->dynticks_nesting--; + WARN_ON_ONCE(rdtp->dynticks_nesting < 0); + if (rdtp->dynticks_nesting) + trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting); + else + rcu_idle_enter_common(rdtp, oldval); + local_irq_restore(flags); +} + +/* + * rcu_idle_exit_common - inform RCU that current CPU is moving away from idle + * + * 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_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval) +{ 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)); - trace_rcu_dyntick("End"); + rcu_cleanup_after_idle(smp_processor_id()); + trace_rcu_dyntick("End", oldval, rdtp->dynticks_nesting); + if (!is_idle_task(current)) { + struct task_struct *idle = idle_task(smp_processor_id()); + + trace_rcu_dyntick("Error on exit: not idle task", + oldval, rdtp->dynticks_nesting); + ftrace_dump(DUMP_ALL); + 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_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_NESTING 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; + struct rcu_dynticks *rdtp; + long long oldval; + + local_irq_save(flags); + rdtp = &__get_cpu_var(rcu_dynticks); + oldval = rdtp->dynticks_nesting; + WARN_ON_ONCE(oldval != 0); + rdtp->dynticks_nesting = DYNTICK_TASK_NESTING; + rcu_idle_exit_common(rdtp, oldval); + local_irq_restore(flags); +} + +/** + * 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 = &__get_cpu_var(rcu_dynticks); + oldval = rdtp->dynticks_nesting; + rdtp->dynticks_nesting++; + WARN_ON_ONCE(rdtp->dynticks_nesting == 0); + if (oldval) + trace_rcu_dyntick("++=", oldval, rdtp->dynticks_nesting); + else + rcu_idle_exit_common(rdtp, oldval); local_irq_restore(flags); } @@ -442,27 +562,37 @@ void rcu_nmi_exit(void) WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); } +#ifdef CONFIG_PROVE_RCU + /** - * rcu_irq_enter - inform RCU of entry to hard irq context + * rcu_is_cpu_idle - see if RCU thinks that the current CPU is idle * - * If the CPU was idle with dynamic ticks active, this updates the - * rdtp->dynticks to let the RCU handling know that the CPU is active. + * If the current CPU is in its idle loop and is neither in an interrupt + * or NMI handler, return true. */ -void rcu_irq_enter(void) +int rcu_is_cpu_idle(void) { - rcu_exit_nohz(); + int ret; + + preempt_disable(); + ret = (atomic_read(&__get_cpu_var(rcu_dynticks).dynticks) & 0x1) == 0; + preempt_enable(); + return ret; } +EXPORT_SYMBOL(rcu_is_cpu_idle); + +#endif /* #ifdef CONFIG_PROVE_RCU */ /** - * rcu_irq_exit - inform RCU of exit from hard irq context + * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle * - * If the CPU was idle with dynamic ticks active, update the rdp->dynticks - * to put let the RCU handling be aware that the CPU is going back to idle - * with no ticks. + * 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. */ -void rcu_irq_exit(void) +int rcu_is_cpu_rrupt_from_idle(void) { - rcu_enter_nohz(); + return __get_cpu_var(rcu_dynticks).dynticks_nesting <= 1; } #ifdef CONFIG_SMP @@ -475,7 +605,7 @@ void rcu_irq_exit(void) static int dyntick_save_progress_counter(struct rcu_data *rdp) { rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks); - return 0; + return (rdp->dynticks_snap & 0x1) == 0; } /* @@ -512,26 +642,6 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) #endif /* #ifdef CONFIG_SMP */ -#else /* #ifdef CONFIG_NO_HZ */ - -#ifdef CONFIG_SMP - -static int dyntick_save_progress_counter(struct rcu_data *rdp) -{ - return 0; -} - -static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) -{ - return rcu_implicit_offline_qs(rdp); -} - -#endif /* #ifdef CONFIG_SMP */ - -#endif /* #else #ifdef CONFIG_NO_HZ */ - -int rcu_cpu_stall_suppress __read_mostly; - static void record_gp_stall_check_time(struct rcu_state *rsp) { rsp->gp_start = jiffies; @@ -866,8 +976,8 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags) /* Advance to a new grace period and initialize state. */ rsp->gpnum++; trace_rcu_grace_period(rsp->name, rsp->gpnum, "start"); - WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT); - rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */ + WARN_ON_ONCE(rsp->fqs_state == RCU_GP_INIT); + rsp->fqs_state = RCU_GP_INIT; /* Hold off force_quiescent_state. */ rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; record_gp_stall_check_time(rsp); @@ -877,7 +987,7 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags) rnp->qsmask = rnp->qsmaskinit; rnp->gpnum = rsp->gpnum; rnp->completed = rsp->completed; - rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */ + rsp->fqs_state = RCU_SIGNAL_INIT; /* force_quiescent_state OK */ rcu_start_gp_per_cpu(rsp, rnp, rdp); rcu_preempt_boost_start_gp(rnp); trace_rcu_grace_period_init(rsp->name, rnp->gpnum, @@ -927,7 +1037,7 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags) rnp = rcu_get_root(rsp); raw_spin_lock(&rnp->lock); /* irqs already disabled. */ - rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */ + rsp->fqs_state = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */ raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ raw_spin_unlock_irqrestore(&rsp->onofflock, flags); } @@ -991,7 +1101,7 @@ static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) rsp->completed = rsp->gpnum; /* Declare the grace period complete. */ trace_rcu_grace_period(rsp->name, rsp->completed, "end"); - rsp->signaled = RCU_GP_IDLE; + rsp->fqs_state = RCU_GP_IDLE; rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */ } @@ -1221,7 +1331,7 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) else raw_spin_unlock_irqrestore(&rnp->lock, flags); if (need_report & RCU_OFL_TASKS_EXP_GP) - rcu_report_exp_rnp(rsp, rnp); + rcu_report_exp_rnp(rsp, rnp, true); rcu_node_kthread_setaffinity(rnp, -1); } @@ -1263,7 +1373,9 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) /* If no callbacks are ready, just return.*/ if (!cpu_has_callbacks_ready_to_invoke(rdp)) { trace_rcu_batch_start(rsp->name, 0, 0); - trace_rcu_batch_end(rsp->name, 0); + trace_rcu_batch_end(rsp->name, 0, !!ACCESS_ONCE(rdp->nxtlist), + need_resched(), is_idle_task(current), + rcu_is_callbacks_kthread()); return; } @@ -1291,12 +1403,17 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) debug_rcu_head_unqueue(list); __rcu_reclaim(rsp->name, list); list = next; - if (++count >= bl) + /* 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); + 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. */ rdp->qlen -= count; @@ -1334,16 +1451,14 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). * Also schedule RCU core processing. * - * This function must be called with hardirqs disabled. It is normally + * 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("Start scheduler-tick"); - if (user || - (idle_cpu(cpu) && rcu_scheduler_active && - !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) { + if (user || rcu_is_cpu_rrupt_from_idle()) { /* * Get here if this CPU took its interrupt from user @@ -1457,7 +1572,7 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed) goto unlock_fqs_ret; /* no GP in progress, time updated. */ } rsp->fqs_active = 1; - switch (rsp->signaled) { + switch (rsp->fqs_state) { case RCU_GP_IDLE: case RCU_GP_INIT: @@ -1473,7 +1588,7 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed) force_qs_rnp(rsp, dyntick_save_progress_counter); raw_spin_lock(&rnp->lock); /* irqs already disabled */ if (rcu_gp_in_progress(rsp)) - rsp->signaled = RCU_FORCE_QS; + rsp->fqs_state = RCU_FORCE_QS; break; case RCU_FORCE_QS: @@ -1812,7 +1927,7 @@ static int rcu_pending(int cpu) * by the current CPU, even if none need be done immediately, returning * 1 if so. */ -static int rcu_needs_cpu_quick_check(int cpu) +static int rcu_cpu_has_callbacks(int cpu) { /* RCU callbacks either ready or pending? */ return per_cpu(rcu_sched_data, cpu).nxtlist || @@ -1913,9 +2028,9 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) for (i = 0; i < RCU_NEXT_SIZE; i++) rdp->nxttail[i] = &rdp->nxtlist; rdp->qlen = 0; -#ifdef CONFIG_NO_HZ rdp->dynticks = &per_cpu(rcu_dynticks, cpu); -#endif /* #ifdef CONFIG_NO_HZ */ + WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_NESTING); + WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1); rdp->cpu = cpu; rdp->rsp = rsp; raw_spin_unlock_irqrestore(&rnp->lock, flags); @@ -1942,6 +2057,10 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) rdp->qlen_last_fqs_check = 0; rdp->n_force_qs_snap = rsp->n_force_qs; rdp->blimit = blimit; + rdp->dynticks->dynticks_nesting = DYNTICK_TASK_NESTING; + atomic_set(&rdp->dynticks->dynticks, + (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1); + rcu_prepare_for_idle_init(cpu); raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ /* @@ -2023,6 +2142,7 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self, rcu_send_cbs_to_online(&rcu_bh_state); rcu_send_cbs_to_online(&rcu_sched_state); rcu_preempt_send_cbs_to_online(); + rcu_cleanup_after_idle(cpu); break; case CPU_DEAD: case CPU_DEAD_FROZEN: diff --git a/kernel/rcutree.h b/kernel/rcutree.h index 849ce9ec51fe..fddff92d6676 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -84,9 +84,10 @@ * Dynticks per-CPU state. */ struct rcu_dynticks { - int dynticks_nesting; /* Track irq/process nesting level. */ - int dynticks_nmi_nesting; /* Track NMI nesting level. */ - atomic_t dynticks; /* Even value for dynticks-idle, else odd. */ + long long dynticks_nesting; /* Track irq/process nesting level. */ + /* Process level is worth LLONG_MAX/2. */ + int dynticks_nmi_nesting; /* Track NMI nesting level. */ + atomic_t dynticks; /* Even value for idle, else odd. */ }; /* RCU's kthread states for tracing. */ @@ -274,16 +275,12 @@ struct rcu_data { /* did other CPU force QS recently? */ long blimit; /* Upper limit on a processed batch */ -#ifdef CONFIG_NO_HZ /* 3) dynticks interface. */ struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */ int dynticks_snap; /* Per-GP tracking for dynticks. */ -#endif /* #ifdef CONFIG_NO_HZ */ /* 4) reasons this CPU needed to be kicked by force_quiescent_state */ -#ifdef CONFIG_NO_HZ unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */ -#endif /* #ifdef CONFIG_NO_HZ */ unsigned long offline_fqs; /* Kicked due to being offline. */ unsigned long resched_ipi; /* Sent a resched IPI. */ @@ -302,16 +299,12 @@ struct rcu_data { struct rcu_state *rsp; }; -/* Values for signaled field in struct rcu_state. */ +/* Values for fqs_state field in struct rcu_state. */ #define RCU_GP_IDLE 0 /* No grace period in progress. */ #define RCU_GP_INIT 1 /* Grace period being initialized. */ #define RCU_SAVE_DYNTICK 2 /* Need to scan dyntick state. */ #define RCU_FORCE_QS 3 /* Need to force quiescent state. */ -#ifdef CONFIG_NO_HZ #define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK -#else /* #ifdef CONFIG_NO_HZ */ -#define RCU_SIGNAL_INIT RCU_FORCE_QS -#endif /* #else #ifdef CONFIG_NO_HZ */ #define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */ @@ -361,7 +354,7 @@ struct rcu_state { /* The following fields are guarded by the root rcu_node's lock. */ - u8 signaled ____cacheline_internodealigned_in_smp; + u8 fqs_state ____cacheline_internodealigned_in_smp; /* Force QS state. */ u8 fqs_active; /* force_quiescent_state() */ /* is running. */ @@ -451,7 +444,8 @@ static void rcu_preempt_check_callbacks(int cpu); static void rcu_preempt_process_callbacks(void); void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)); #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) -static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp); +static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, + bool wake); #endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) */ static int rcu_preempt_pending(int cpu); static int rcu_preempt_needs_cpu(int cpu); @@ -461,6 +455,7 @@ static void __init __rcu_init_preempt(void); static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags); static void rcu_preempt_boost_start_gp(struct rcu_node *rnp); static void invoke_rcu_callbacks_kthread(void); +static bool rcu_is_callbacks_kthread(void); #ifdef CONFIG_RCU_BOOST static void rcu_preempt_do_callbacks(void); static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, @@ -473,5 +468,8 @@ static void rcu_yield(void (*f)(unsigned long), unsigned long arg); #endif /* #ifdef CONFIG_RCU_BOOST */ static void rcu_cpu_kthread_setrt(int cpu, int to_rt); static void __cpuinit rcu_prepare_kthreads(int cpu); +static void rcu_prepare_for_idle_init(int cpu); +static void rcu_cleanup_after_idle(int cpu); +static void rcu_prepare_for_idle(int cpu); #endif /* #ifndef RCU_TREE_NONCORE */ diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 4b9b9f8a4184..8bb35d73e1f9 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -312,6 +312,7 @@ static noinline void rcu_read_unlock_special(struct task_struct *t) { int empty; int empty_exp; + int empty_exp_now; unsigned long flags; struct list_head *np; #ifdef CONFIG_RCU_BOOST @@ -382,8 +383,10 @@ static noinline void rcu_read_unlock_special(struct task_struct *t) /* * If this was the last task on the current list, and if * we aren't waiting on any CPUs, report the quiescent state. - * Note that rcu_report_unblock_qs_rnp() releases rnp->lock. + * Note that rcu_report_unblock_qs_rnp() releases rnp->lock, + * so we must take a snapshot of the expedited state. */ + empty_exp_now = !rcu_preempted_readers_exp(rnp); if (!empty && !rcu_preempt_blocked_readers_cgp(rnp)) { trace_rcu_quiescent_state_report("preempt_rcu", rnp->gpnum, @@ -406,8 +409,8 @@ static noinline void rcu_read_unlock_special(struct task_struct *t) * If this was the last task on the expedited lists, * then we need to report up the rcu_node hierarchy. */ - if (!empty_exp && !rcu_preempted_readers_exp(rnp)) - rcu_report_exp_rnp(&rcu_preempt_state, rnp); + if (!empty_exp && empty_exp_now) + rcu_report_exp_rnp(&rcu_preempt_state, rnp, true); } else { local_irq_restore(flags); } @@ -729,9 +732,13 @@ static int sync_rcu_preempt_exp_done(struct rcu_node *rnp) * recursively up the tree. (Calm down, calm down, we do the recursion * iteratively!) * + * Most callers will set the "wake" flag, but the task initiating the + * expedited grace period need not wake itself. + * * Caller must hold sync_rcu_preempt_exp_mutex. */ -static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp) +static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, + bool wake) { unsigned long flags; unsigned long mask; @@ -744,7 +751,8 @@ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp) } if (rnp->parent == NULL) { raw_spin_unlock_irqrestore(&rnp->lock, flags); - wake_up(&sync_rcu_preempt_exp_wq); + if (wake) + wake_up(&sync_rcu_preempt_exp_wq); break; } mask = rnp->grpmask; @@ -777,7 +785,7 @@ sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp) must_wait = 1; } if (!must_wait) - rcu_report_exp_rnp(rsp, rnp); + rcu_report_exp_rnp(rsp, rnp, false); /* Don't wake self. */ } /* @@ -1069,9 +1077,9 @@ EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); * report on tasks preempted in RCU read-side critical sections during * expedited RCU grace periods. */ -static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp) +static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, + bool wake) { - return; } #endif /* #ifdef CONFIG_HOTPLUG_CPU */ @@ -1157,8 +1165,6 @@ static void rcu_initiate_boost_trace(struct rcu_node *rnp) #endif /* #else #ifdef CONFIG_RCU_TRACE */ -static struct lock_class_key rcu_boost_class; - /* * Carry out RCU priority boosting on the task indicated by ->exp_tasks * or ->boost_tasks, advancing the pointer to the next task in the @@ -1221,15 +1227,13 @@ static int rcu_boost(struct rcu_node *rnp) */ t = container_of(tb, struct task_struct, rcu_node_entry); rt_mutex_init_proxy_locked(&mtx, t); - /* Avoid lockdep false positives. This rt_mutex is its own thing. */ - lockdep_set_class_and_name(&mtx.wait_lock, &rcu_boost_class, - "rcu_boost_mutex"); t->rcu_boost_mutex = &mtx; raw_spin_unlock_irqrestore(&rnp->lock, flags); rt_mutex_lock(&mtx); /* Side effect: boosts task t's priority. */ rt_mutex_unlock(&mtx); /* Keep lockdep happy. */ - return rnp->exp_tasks != NULL || rnp->boost_tasks != NULL; + return ACCESS_ONCE(rnp->exp_tasks) != NULL || + ACCESS_ONCE(rnp->boost_tasks) != NULL; } /* @@ -1329,6 +1333,15 @@ static void invoke_rcu_callbacks_kthread(void) } /* + * Is the current CPU running the RCU-callbacks kthread? + * Caller must have preemption disabled. + */ +static bool rcu_is_callbacks_kthread(void) +{ + return __get_cpu_var(rcu_cpu_kthread_task) == current; +} + +/* * Set the affinity of the boost kthread. The CPU-hotplug locks are * held, so no one should be messing with the existence of the boost * kthread. @@ -1772,6 +1785,11 @@ static void invoke_rcu_callbacks_kthread(void) WARN_ON_ONCE(1); } +static bool rcu_is_callbacks_kthread(void) +{ + return false; +} + static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) { } @@ -1907,7 +1925,7 @@ void synchronize_sched_expedited(void) * grace period works for us. */ get_online_cpus(); - snap = atomic_read(&sync_sched_expedited_started) - 1; + snap = atomic_read(&sync_sched_expedited_started); smp_mb(); /* ensure read is before try_stop_cpus(). */ } @@ -1939,88 +1957,243 @@ EXPORT_SYMBOL_GPL(synchronize_sched_expedited); * 1 if so. This function is part of the RCU implementation; it is -not- * an exported member of the RCU API. * - * Because we have preemptible RCU, just check whether this CPU needs - * any flavor of RCU. Do not chew up lots of CPU cycles with preemption - * disabled in a most-likely vain attempt to cause RCU not to need this CPU. + * Because we not have RCU_FAST_NO_HZ, just check whether this CPU needs + * any flavor of RCU. */ int rcu_needs_cpu(int cpu) { - return rcu_needs_cpu_quick_check(cpu); + return rcu_cpu_has_callbacks(cpu); +} + +/* + * Because we do not have RCU_FAST_NO_HZ, don't bother initializing for it. + */ +static void rcu_prepare_for_idle_init(int cpu) +{ +} + +/* + * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up + * after it. + */ +static void rcu_cleanup_after_idle(int cpu) +{ +} + +/* + * Do the idle-entry grace-period work, which, because CONFIG_RCU_FAST_NO_HZ=y, + * is nothing. + */ +static void rcu_prepare_for_idle(int cpu) +{ } #else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */ -#define RCU_NEEDS_CPU_FLUSHES 5 +/* + * This code is invoked when a CPU goes idle, at which point we want + * to have the CPU do everything required for RCU so that it can enter + * the energy-efficient dyntick-idle mode. This is handled by a + * state machine implemented by rcu_prepare_for_idle() below. + * + * The following three proprocessor symbols control this state machine: + * + * RCU_IDLE_FLUSHES gives the maximum number of times that we will attempt + * to satisfy RCU. Beyond this point, it is better to incur a periodic + * scheduling-clock interrupt than to loop through the state machine + * at full power. + * RCU_IDLE_OPT_FLUSHES gives the number of RCU_IDLE_FLUSHES that are + * optional if RCU does not need anything immediately from this + * CPU, even if this CPU still has RCU callbacks queued. The first + * times through the state machine are mandatory: we need to give + * the state machine a chance to communicate a quiescent state + * to the RCU core. + * RCU_IDLE_GP_DELAY gives the number of jiffies that a CPU is permitted + * to sleep in dyntick-idle mode with RCU callbacks pending. This + * is sized to be roughly one RCU grace period. Those energy-efficiency + * benchmarkers who might otherwise be tempted to set this to a large + * number, be warned: Setting RCU_IDLE_GP_DELAY too high can hang your + * system. And if you are -that- concerned about energy efficiency, + * just power the system down and be done with it! + * + * The values below work well in practice. If future workloads require + * adjustment, they can be converted into kernel config parameters, though + * making the state machine smarter might be a better option. + */ +#define RCU_IDLE_FLUSHES 5 /* Number of dyntick-idle tries. */ +#define RCU_IDLE_OPT_FLUSHES 3 /* Optional dyntick-idle tries. */ +#define RCU_IDLE_GP_DELAY 6 /* Roughly one grace period. */ + static DEFINE_PER_CPU(int, rcu_dyntick_drain); static DEFINE_PER_CPU(unsigned long, rcu_dyntick_holdoff); +static DEFINE_PER_CPU(struct hrtimer, rcu_idle_gp_timer); +static ktime_t rcu_idle_gp_wait; /* - * Check to see if any future RCU-related work will need to be done - * by the current CPU, even if none need be done immediately, returning - * 1 if so. This function is part of the RCU implementation; it is -not- - * an exported member of the RCU API. + * Allow the CPU to enter dyntick-idle mode if either: (1) There are no + * callbacks on this CPU, (2) this CPU has not yet attempted to enter + * dyntick-idle mode, or (3) this CPU is in the process of attempting to + * enter dyntick-idle mode. Otherwise, if we have recently tried and failed + * to enter dyntick-idle mode, we refuse to try to enter it. After all, + * it is better to incur scheduling-clock interrupts than to spin + * continuously for the same time duration! + */ +int rcu_needs_cpu(int cpu) +{ + /* If no callbacks, RCU doesn't need the CPU. */ + if (!rcu_cpu_has_callbacks(cpu)) + return 0; + /* Otherwise, RCU needs the CPU only if it recently tried and failed. */ + return per_cpu(rcu_dyntick_holdoff, cpu) == jiffies; +} + +/* + * Timer handler used to force CPU to start pushing its remaining RCU + * callbacks in the case where it entered dyntick-idle mode with callbacks + * pending. The hander doesn't really need to do anything because the + * real work is done upon re-entry to idle, or by the next scheduling-clock + * interrupt should idle not be re-entered. + */ +static enum hrtimer_restart rcu_idle_gp_timer_func(struct hrtimer *hrtp) +{ + trace_rcu_prep_idle("Timer"); + return HRTIMER_NORESTART; +} + +/* + * Initialize the timer used to pull CPUs out of dyntick-idle mode. + */ +static void rcu_prepare_for_idle_init(int cpu) +{ + static int firsttime = 1; + struct hrtimer *hrtp = &per_cpu(rcu_idle_gp_timer, cpu); + + hrtimer_init(hrtp, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + hrtp->function = rcu_idle_gp_timer_func; + if (firsttime) { + unsigned int upj = jiffies_to_usecs(RCU_IDLE_GP_DELAY); + + rcu_idle_gp_wait = ns_to_ktime(upj * (u64)1000); + firsttime = 0; + } +} + +/* + * Clean up for exit from idle. Because we are exiting from idle, there + * is no longer any point to rcu_idle_gp_timer, so cancel it. This will + * do nothing if this timer is not active, so just cancel it unconditionally. + */ +static void rcu_cleanup_after_idle(int cpu) +{ + hrtimer_cancel(&per_cpu(rcu_idle_gp_timer, cpu)); +} + +/* + * Check to see if any RCU-related work can be done by the current CPU, + * and if so, schedule a softirq to get it done. This function is part + * of the RCU implementation; it is -not- an exported member of the RCU API. * - * Because we are not supporting preemptible RCU, attempt to accelerate - * any current grace periods so that RCU no longer needs this CPU, but - * only if all other CPUs are already in dynticks-idle mode. This will - * allow the CPU cores to be powered down immediately, as opposed to after - * waiting many milliseconds for grace periods to elapse. + * The idea is for the current CPU to clear out all work required by the + * RCU core for the current grace period, so that this CPU can be permitted + * to enter dyntick-idle mode. In some cases, it will need to be awakened + * at the end of the grace period by whatever CPU ends the grace period. + * This allows CPUs to go dyntick-idle more quickly, and to reduce the + * number of wakeups by a modest integer factor. * * Because it is not legal to invoke rcu_process_callbacks() with irqs * disabled, we do one pass of force_quiescent_state(), then do a * invoke_rcu_core() to cause rcu_process_callbacks() to be invoked * later. The per-cpu rcu_dyntick_drain variable controls the sequencing. + * + * The caller must have disabled interrupts. */ -int rcu_needs_cpu(int cpu) +static void rcu_prepare_for_idle(int cpu) { - int c = 0; - int snap; - int thatcpu; - - /* Check for being in the holdoff period. */ - if (per_cpu(rcu_dyntick_holdoff, cpu) == jiffies) - return rcu_needs_cpu_quick_check(cpu); - - /* Don't bother unless we are the last non-dyntick-idle CPU. */ - for_each_online_cpu(thatcpu) { - if (thatcpu == cpu) - continue; - snap = atomic_add_return(0, &per_cpu(rcu_dynticks, - thatcpu).dynticks); - smp_mb(); /* Order sampling of snap with end of grace period. */ - if ((snap & 0x1) != 0) { - per_cpu(rcu_dyntick_drain, cpu) = 0; - per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1; - return rcu_needs_cpu_quick_check(cpu); - } + unsigned long flags; + + local_irq_save(flags); + + /* + * If there are no callbacks on this CPU, enter dyntick-idle mode. + * Also reset state to avoid prejudicing later attempts. + */ + if (!rcu_cpu_has_callbacks(cpu)) { + per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1; + per_cpu(rcu_dyntick_drain, cpu) = 0; + local_irq_restore(flags); + trace_rcu_prep_idle("No callbacks"); + return; + } + + /* + * If in holdoff mode, just return. We will presumably have + * refrained from disabling the scheduling-clock tick. + */ + if (per_cpu(rcu_dyntick_holdoff, cpu) == jiffies) { + local_irq_restore(flags); + trace_rcu_prep_idle("In holdoff"); + return; } /* Check and update the rcu_dyntick_drain sequencing. */ if (per_cpu(rcu_dyntick_drain, cpu) <= 0) { /* First time through, initialize the counter. */ - per_cpu(rcu_dyntick_drain, cpu) = RCU_NEEDS_CPU_FLUSHES; + per_cpu(rcu_dyntick_drain, cpu) = RCU_IDLE_FLUSHES; + } else if (per_cpu(rcu_dyntick_drain, cpu) <= RCU_IDLE_OPT_FLUSHES && + !rcu_pending(cpu)) { + /* Can we go dyntick-idle despite still having callbacks? */ + trace_rcu_prep_idle("Dyntick with callbacks"); + per_cpu(rcu_dyntick_drain, cpu) = 0; + per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1; + hrtimer_start(&per_cpu(rcu_idle_gp_timer, cpu), + rcu_idle_gp_wait, HRTIMER_MODE_REL); + return; /* Nothing more to do immediately. */ } else if (--per_cpu(rcu_dyntick_drain, cpu) <= 0) { /* We have hit the limit, so time to give up. */ per_cpu(rcu_dyntick_holdoff, cpu) = jiffies; - return rcu_needs_cpu_quick_check(cpu); + local_irq_restore(flags); + trace_rcu_prep_idle("Begin holdoff"); + invoke_rcu_core(); /* Force the CPU out of dyntick-idle. */ + return; } - /* Do one step pushing remaining RCU callbacks through. */ + /* + * Do one step of pushing the remaining RCU callbacks through + * the RCU core state machine. + */ +#ifdef CONFIG_TREE_PREEMPT_RCU + if (per_cpu(rcu_preempt_data, cpu).nxtlist) { + local_irq_restore(flags); + rcu_preempt_qs(cpu); + force_quiescent_state(&rcu_preempt_state, 0); + local_irq_save(flags); + } +#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ if (per_cpu(rcu_sched_data, cpu).nxtlist) { + local_irq_restore(flags); rcu_sched_qs(cpu); force_quiescent_state(&rcu_sched_state, 0); - c = c || per_cpu(rcu_sched_data, cpu).nxtlist; + local_irq_save(flags); } if (per_cpu(rcu_bh_data, cpu).nxtlist) { + local_irq_restore(flags); rcu_bh_qs(cpu); force_quiescent_state(&rcu_bh_state, 0); - c = c || per_cpu(rcu_bh_data, cpu).nxtlist; + local_irq_save(flags); } - /* If RCU callbacks are still pending, RCU still needs this CPU. */ - if (c) + /* + * If RCU callbacks are still pending, RCU still needs this CPU. + * So try forcing the callbacks through the grace period. + */ + if (rcu_cpu_has_callbacks(cpu)) { + local_irq_restore(flags); + trace_rcu_prep_idle("More callbacks"); invoke_rcu_core(); - return c; + } else { + local_irq_restore(flags); + trace_rcu_prep_idle("Callbacks drained"); + } } #endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */ diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c index 9feffa4c0695..654cfe67f0d1 100644 --- a/kernel/rcutree_trace.c +++ b/kernel/rcutree_trace.c @@ -67,13 +67,11 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) rdp->completed, rdp->gpnum, rdp->passed_quiesce, rdp->passed_quiesce_gpnum, rdp->qs_pending); -#ifdef CONFIG_NO_HZ - seq_printf(m, " dt=%d/%d/%d df=%lu", + seq_printf(m, " dt=%d/%llx/%d df=%lu", atomic_read(&rdp->dynticks->dynticks), rdp->dynticks->dynticks_nesting, rdp->dynticks->dynticks_nmi_nesting, rdp->dynticks_fqs); -#endif /* #ifdef CONFIG_NO_HZ */ seq_printf(m, " of=%lu ri=%lu", rdp->offline_fqs, rdp->resched_ipi); seq_printf(m, " ql=%ld qs=%c%c%c%c", rdp->qlen, @@ -141,13 +139,11 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp) rdp->completed, rdp->gpnum, rdp->passed_quiesce, rdp->passed_quiesce_gpnum, rdp->qs_pending); -#ifdef CONFIG_NO_HZ - seq_printf(m, ",%d,%d,%d,%lu", + seq_printf(m, ",%d,%llx,%d,%lu", atomic_read(&rdp->dynticks->dynticks), rdp->dynticks->dynticks_nesting, rdp->dynticks->dynticks_nmi_nesting, rdp->dynticks_fqs); -#endif /* #ifdef CONFIG_NO_HZ */ seq_printf(m, ",%lu,%lu", rdp->offline_fqs, rdp->resched_ipi); seq_printf(m, ",%ld,\"%c%c%c%c\"", rdp->qlen, ".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] != @@ -171,9 +167,7 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp) static int show_rcudata_csv(struct seq_file *m, void *unused) { seq_puts(m, "\"CPU\",\"Online?\",\"c\",\"g\",\"pq\",\"pgp\",\"pq\","); -#ifdef CONFIG_NO_HZ seq_puts(m, "\"dt\",\"dt nesting\",\"dt NMI nesting\",\"df\","); -#endif /* #ifdef CONFIG_NO_HZ */ seq_puts(m, "\"of\",\"ri\",\"ql\",\"qs\""); #ifdef CONFIG_RCU_BOOST seq_puts(m, "\"kt\",\"ktl\""); @@ -278,7 +272,7 @@ static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp) gpnum = rsp->gpnum; seq_printf(m, "c=%lu g=%lu s=%d jfq=%ld j=%x " "nfqs=%lu/nfqsng=%lu(%lu) fqlh=%lu\n", - rsp->completed, gpnum, rsp->signaled, + rsp->completed, gpnum, rsp->fqs_state, (long)(rsp->jiffies_force_qs - jiffies), (int)(jiffies & 0xffff), rsp->n_force_qs, rsp->n_force_qs_ngp, diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c index f9d8482dd487..a242e691c993 100644 --- a/kernel/rtmutex.c +++ b/kernel/rtmutex.c @@ -579,7 +579,6 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state, struct rt_mutex_waiter *waiter) { int ret = 0; - int was_disabled; for (;;) { /* Try to acquire the lock: */ @@ -602,17 +601,10 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state, raw_spin_unlock(&lock->wait_lock); - was_disabled = irqs_disabled(); - if (was_disabled) - local_irq_enable(); - debug_rt_mutex_print_deadlock(waiter); schedule_rt_mutex(lock); - if (was_disabled) - local_irq_disable(); - raw_spin_lock(&lock->wait_lock); set_current_state(state); } diff --git a/kernel/softirq.c b/kernel/softirq.c index 2c71d91efff0..4eb3a0fa351e 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -347,12 +347,12 @@ void irq_exit(void) if (!in_interrupt() && local_softirq_pending()) invoke_softirq(); - rcu_irq_exit(); #ifdef CONFIG_NO_HZ /* Make sure that timer wheel updates are propagated */ if (idle_cpu(smp_processor_id()) && !in_interrupt() && !need_resched()) - tick_nohz_stop_sched_tick(0); + tick_nohz_irq_exit(); #endif + rcu_irq_exit(); preempt_enable_no_resched(); } diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 40420644d0ba..0ec8b832ab6b 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -275,42 +275,17 @@ u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time) } EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us); -/** - * tick_nohz_stop_sched_tick - stop the idle tick from the idle task - * - * When the next event is more than a tick into the future, stop the idle tick - * Called either from the idle loop or from irq_exit() when an idle period was - * just interrupted by an interrupt which did not cause a reschedule. - */ -void tick_nohz_stop_sched_tick(int inidle) +static void tick_nohz_stop_sched_tick(struct tick_sched *ts) { - unsigned long seq, last_jiffies, next_jiffies, delta_jiffies, flags; - struct tick_sched *ts; + unsigned long seq, last_jiffies, next_jiffies, delta_jiffies; ktime_t last_update, expires, now; struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev; u64 time_delta; int cpu; - local_irq_save(flags); - cpu = smp_processor_id(); ts = &per_cpu(tick_cpu_sched, cpu); - /* - * Call to tick_nohz_start_idle stops the last_update_time from being - * updated. Thus, it must not be called in the event we are called from - * irq_exit() with the prior state different than idle. - */ - if (!inidle && !ts->inidle) - goto end; - - /* - * Set ts->inidle unconditionally. Even if the system did not - * switch to NOHZ mode the cpu frequency governers rely on the - * update of the idle time accounting in tick_nohz_start_idle(). - */ - ts->inidle = 1; - now = tick_nohz_start_idle(cpu, ts); /* @@ -326,10 +301,10 @@ void tick_nohz_stop_sched_tick(int inidle) } if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) - goto end; + return; if (need_resched()) - goto end; + return; if (unlikely(local_softirq_pending() && cpu_online(cpu))) { static int ratelimit; @@ -339,7 +314,7 @@ void tick_nohz_stop_sched_tick(int inidle) (unsigned int) local_softirq_pending()); ratelimit++; } - goto end; + return; } ts->idle_calls++; @@ -434,7 +409,6 @@ void tick_nohz_stop_sched_tick(int inidle) ts->idle_tick = hrtimer_get_expires(&ts->sched_timer); ts->tick_stopped = 1; ts->idle_jiffies = last_jiffies; - rcu_enter_nohz(); } ts->idle_sleeps++; @@ -472,8 +446,56 @@ out: ts->next_jiffies = next_jiffies; ts->last_jiffies = last_jiffies; ts->sleep_length = ktime_sub(dev->next_event, now); -end: - local_irq_restore(flags); +} + +/** + * tick_nohz_idle_enter - stop the idle tick from the idle task + * + * When the next event is more than a tick into the future, stop the idle tick + * Called when we start the idle loop. + * + * The arch is responsible of calling: + * + * - rcu_idle_enter() after its last use of RCU before the CPU is put + * to sleep. + * - rcu_idle_exit() before the first use of RCU after the CPU is woken up. + */ +void tick_nohz_idle_enter(void) +{ + struct tick_sched *ts; + + WARN_ON_ONCE(irqs_disabled()); + + local_irq_disable(); + + ts = &__get_cpu_var(tick_cpu_sched); + /* + * set ts->inidle unconditionally. even if the system did not + * switch to nohz mode the cpu frequency governers rely on the + * update of the idle time accounting in tick_nohz_start_idle(). + */ + ts->inidle = 1; + tick_nohz_stop_sched_tick(ts); + + local_irq_enable(); +} + +/** + * tick_nohz_irq_exit - update next tick event from interrupt exit + * + * When an interrupt fires while we are idle and it doesn't cause + * a reschedule, it may still add, modify or delete a timer, enqueue + * an RCU callback, etc... + * So we need to re-calculate and reprogram the next tick event. + */ +void tick_nohz_irq_exit(void) +{ + struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); + + if (!ts->inidle) + return; + + tick_nohz_stop_sched_tick(ts); } /** @@ -515,11 +537,13 @@ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now) } /** - * tick_nohz_restart_sched_tick - restart the idle tick from the idle task + * tick_nohz_idle_exit - restart the idle tick from the idle task * * Restart the idle tick when the CPU is woken up from idle + * This also exit the RCU extended quiescent state. The CPU + * can use RCU again after this function is called. */ -void tick_nohz_restart_sched_tick(void) +void tick_nohz_idle_exit(void) { int cpu = smp_processor_id(); struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); @@ -529,6 +553,7 @@ void tick_nohz_restart_sched_tick(void) ktime_t now; local_irq_disable(); + if (ts->idle_active || (ts->inidle && ts->tick_stopped)) now = ktime_get(); @@ -543,8 +568,6 @@ void tick_nohz_restart_sched_tick(void) ts->inidle = 0; - rcu_exit_nohz(); - /* Update jiffies first */ select_nohz_load_balancer(0); tick_do_update_jiffies64(now); diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index f2bd275bb60f..a043d224adf6 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4775,6 +4775,7 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { __ftrace_dump(true, oops_dump_mode); } +EXPORT_SYMBOL_GPL(ftrace_dump); __init static int tracer_alloc_buffers(void) { |