diff options
| author | Frederic Weisbecker <frederic@kernel.org> | 2023-08-13 03:16:18 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-08-16 18:22:04 +0200 |
| commit | c3b954a51b6447d060c1b30ec4efb5db34a056f7 (patch) | |
| tree | e0f2abf6da64768c1955d87141ddec46a7b7b123 | |
| parent | af99918f0e39aeb14d2cd08ca79faf9ccb1ec47f (diff) | |
tick: Detect and fix jiffies update stall
[ Upstream commit a1ff03cd6fb9c501fff63a4a2bface9adcfa81cd ]
tick: Detect and fix jiffies update stall
On some rare cases, the timekeeper CPU may be delaying its jiffies
update duty for a while. Known causes include:
* The timekeeper is waiting on stop_machine in a MULTI_STOP_DISABLE_IRQ
or MULTI_STOP_RUN state. Disabled interrupts prevent from timekeeping
updates while waiting for the target CPU to complete its
stop_machine() callback.
* The timekeeper vcpu has VMEXIT'ed for a long while due to some overload
on the host.
Detect and fix these situations with emergency timekeeping catchups.
Original-patch-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | kernel/time/tick-sched.c | 17 | ||||
| -rw-r--r-- | kernel/time/tick-sched.h | 4 |
2 files changed, 21 insertions, 0 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index f42d0776bc84..7701c720dc1f 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -180,6 +180,8 @@ 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(); @@ -207,6 +209,21 @@ 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; } 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); |