diff options
Diffstat (limited to 'libre/linux-libre/0003-tick-Detect-and-fix-jiffies-update-stall.patch')
-rw-r--r-- | libre/linux-libre/0003-tick-Detect-and-fix-jiffies-update-stall.patch | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/libre/linux-libre/0003-tick-Detect-and-fix-jiffies-update-stall.patch b/libre/linux-libre/0003-tick-Detect-and-fix-jiffies-update-stall.patch new file mode 100644 index 000000000..be56c7108 --- /dev/null +++ b/libre/linux-libre/0003-tick-Detect-and-fix-jiffies-update-stall.patch @@ -0,0 +1,86 @@ +From e3fb9a238974e20ab8a7b56e9f6a19e2acdc9b87 Mon Sep 17 00:00:00 2001 +From: Frederic Weisbecker <frederic@kernel.org> +Date: Wed, 2 Feb 2022 01:01:07 +0100 +Subject: [PATCH 3/9] 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> +--- + kernel/time/tick-sched.c | 17 +++++++++++++++++ + kernel/time/tick-sched.h | 4 ++++ + 2 files changed, 21 insertions(+) + +diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c +index 17a283ce2b20..c89f50a7e690 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; + } +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); +-- +2.35.1 + |