diff options
Diffstat (limited to 'kernel/time')
| -rw-r--r-- | kernel/time/Kconfig | 9 | ||||
| -rw-r--r-- | kernel/time/clocksource.c | 8 | ||||
| -rw-r--r-- | kernel/time/posix-cpu-timers.c | 12 | ||||
| -rw-r--r-- | kernel/time/tick-sched.c | 77 | ||||
| -rw-r--r-- | kernel/time/tick-sched.h | 4 |
5 files changed, 90 insertions, 20 deletions
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig index 04bfd62f5e5c..27b7868b5c30 100644 --- a/kernel/time/Kconfig +++ b/kernel/time/Kconfig @@ -181,5 +181,14 @@ config HIGH_RES_TIMERS hardware is not capable then this option only increases the size of the kernel image. +config CLOCKSOURCE_WATCHDOG_MAX_SKEW_US + int "Clocksource watchdog maximum allowable skew (in μs)" + depends on CLOCKSOURCE_WATCHDOG + range 50 1000 + default 100 + help + Specify the maximum amount of allowable watchdog skew in + microseconds before reporting the clocksource to be unstable. + endmenu endif diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index 1cf73807b450..95d7ca35bdf2 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -107,7 +107,13 @@ static u64 suspend_start; * This delay could be due to SMIs, NMIs, or to VCPU preemptions. Used as * a lower bound for cs->uncertainty_margin values when registering clocks. */ -#define WATCHDOG_MAX_SKEW (100 * NSEC_PER_USEC) +#ifdef CONFIG_CLOCKSOURCE_WATCHDOG_MAX_SKEW_US +#define MAX_SKEW_USEC CONFIG_CLOCKSOURCE_WATCHDOG_MAX_SKEW_US +#else +#define MAX_SKEW_USEC 100 +#endif + +#define WATCHDOG_MAX_SKEW (MAX_SKEW_USEC * NSEC_PER_USEC) #ifdef CONFIG_CLOCKSOURCE_WATCHDOG static void clocksource_watchdog_work(struct work_struct *work); diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 9190d9eb236d..0a97193984db 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -35,14 +35,20 @@ void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit) * tsk->signal->posix_cputimers.bases[clock].nextevt expiration cache if * necessary. Needs siglock protection since other code may update the * expiration cache as well. + * + * Returns 0 on success, -ESRCH on failure. Can fail if the task is exiting and + * we cannot lock_task_sighand. Cannot fail if task is current. */ -void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new) +int update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new) { u64 nsecs = rlim_new * NSEC_PER_SEC; + unsigned long irq_fl; - spin_lock_irq(&task->sighand->siglock); + if (!lock_task_sighand(task, &irq_fl)) + return -ESRCH; set_process_cpu_timer(task, CPUCLOCK_PROF, &nsecs, NULL); - spin_unlock_irq(&task->sighand->siglock); + unlock_task_sighand(task, &irq_fl); + return 0; } /* diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 17a283ce2b20..2d76c91b85de 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -169,6 +169,8 @@ static ktime_t tick_init_jiffy_update(void) return period; } +#define MAX_STALLED_JIFFIES 5 + static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now) { int cpu = smp_processor_id(); @@ -196,6 +198,21 @@ static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now) if (tick_do_timer_cpu == cpu) tick_do_update_jiffies64(now); + /* + * If jiffies update stalled for too long (timekeeper in stop_machine() + * or VMEXIT'ed for several msecs), force an update. + */ + if (ts->last_tick_jiffies != jiffies) { + ts->stalled_jiffies = 0; + ts->last_tick_jiffies = READ_ONCE(jiffies); + } else { + if (++ts->stalled_jiffies == MAX_STALLED_JIFFIES) { + tick_do_update_jiffies64(now); + ts->stalled_jiffies = 0; + ts->last_tick_jiffies = READ_ONCE(jiffies); + } + } + if (ts->inidle) ts->got_idle_tick = 1; } @@ -768,7 +785,7 @@ static inline bool local_timer_softirq_pending(void) static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu) { - u64 basemono, next_tick, next_tmr, next_rcu, delta, expires; + u64 basemono, next_tick, delta, expires; unsigned long basejiff; unsigned int seq; @@ -791,7 +808,7 @@ static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu) * minimal delta which brings us back to this place * immediately. Lather, rinse and repeat... */ - if (rcu_needs_cpu(basemono, &next_rcu) || arch_needs_cpu() || + if (rcu_needs_cpu() || arch_needs_cpu() || irq_work_needs_cpu() || local_timer_softirq_pending()) { next_tick = basemono + TICK_NSEC; } else { @@ -802,10 +819,8 @@ static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu) * disabled this also looks at the next expiring * hrtimer. */ - next_tmr = get_next_timer_interrupt(basejiff, basemono); - ts->next_timer = next_tmr; - /* Take the next rcu event into account */ - next_tick = next_rcu < next_tmr ? next_rcu : next_tmr; + next_tick = get_next_timer_interrupt(basejiff, basemono); + ts->next_timer = next_tick; } /* @@ -984,6 +999,45 @@ static void tick_nohz_full_update_tick(struct tick_sched *ts) __tick_nohz_full_update_tick(ts, ktime_get()); } +/* + * A pending softirq outside an IRQ (or softirq disabled section) context + * should be waiting for ksoftirqd to handle it. Therefore we shouldn't + * reach here due to the need_resched() early check in can_stop_idle_tick(). + * + * However if we are between CPUHP_AP_SMPBOOT_THREADS and CPU_TEARDOWN_CPU on the + * cpu_down() process, softirqs can still be raised while ksoftirqd is parked, + * triggering the below since wakep_softirqd() is ignored. + * + */ +static bool report_idle_softirq(void) +{ + static int ratelimit; + unsigned int pending = local_softirq_pending(); + + if (likely(!pending)) + return false; + + /* Some softirqs claim to be safe against hotplug and ksoftirqd parking */ + if (!cpu_active(smp_processor_id())) { + pending &= ~SOFTIRQ_HOTPLUG_SAFE_MASK; + if (!pending) + return false; + } + + if (ratelimit < 10) + return false; + + /* On RT, softirqs handling may be waiting on some lock */ + if (!local_bh_blocked()) + return false; + + pr_warn("NOHZ tick-stop error: local softirq work is pending, handler #%02x!!!\n", + pending); + ratelimit++; + + return true; +} + static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) { /* @@ -1010,17 +1064,8 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) if (need_resched()) return false; - if (unlikely(local_softirq_pending())) { - static int ratelimit; - - if (ratelimit < 10 && !local_bh_blocked() && - (local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) { - pr_warn("NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #%02x!!!\n", - (unsigned int) local_softirq_pending()); - ratelimit++; - } + if (unlikely(report_idle_softirq())) return false; - } if (tick_nohz_full_enabled()) { /* diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h index d952ae393423..504649513399 100644 --- a/kernel/time/tick-sched.h +++ b/kernel/time/tick-sched.h @@ -49,6 +49,8 @@ enum tick_nohz_mode { * @timer_expires_base: Base time clock monotonic for @timer_expires * @next_timer: Expiry time of next expiring timer for debugging purpose only * @tick_dep_mask: Tick dependency mask - is set, if someone needs the tick + * @last_tick_jiffies: Value of jiffies seen on last tick + * @stalled_jiffies: Number of stalled jiffies detected across ticks */ struct tick_sched { struct hrtimer sched_timer; @@ -77,6 +79,8 @@ struct tick_sched { u64 next_timer; ktime_t idle_expires; atomic_t tick_dep_mask; + unsigned long last_tick_jiffies; + unsigned int stalled_jiffies; }; extern struct tick_sched *tick_get_tick_sched(int cpu); |