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| author | Thomas Gleixner <tglx@linutronix.de> | 2020-11-17 14:19:44 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2020-11-19 10:48:28 +0100 |
| commit | c398960cd82b233886fbff163986f998b5a5c008 (patch) | |
| tree | 6d73b864dac7e999941a34ade55baa1b403e2013 /kernel/time | |
| parent | tick/broadcast: Serialize access to tick_next_period (diff) | |
| download | linux-c398960cd82b233886fbff163986f998b5a5c008.tar.xz linux-c398960cd82b233886fbff163986f998b5a5c008.zip | |
tick: Document protections for tick related data
The protection rules for tick_next_period and last_jiffies_update are blury
at best. Clarify this.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201117132006.197713794@linutronix.de
Diffstat (limited to 'kernel/time')
| -rw-r--r-- | kernel/time/tick-common.c | 4 | ||||
| -rw-r--r-- | kernel/time/tick-sched.c | 4 |
2 files changed, 6 insertions, 2 deletions
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c index 6c9c342dd0e5..68504eb0d38b 100644 --- a/kernel/time/tick-common.c +++ b/kernel/time/tick-common.c @@ -27,7 +27,9 @@ */ DEFINE_PER_CPU(struct tick_device, tick_cpu_device); /* - * Tick next event: keeps track of the tick time + * Tick next event: keeps track of the tick time. It's updated by the + * CPU which handles the tick and protected by jiffies_lock. There is + * no requirement to write hold the jiffies seqcount for it. */ ktime_t tick_next_period; ktime_t tick_period; diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 81632cd5e3b7..15360e652c85 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -44,7 +44,9 @@ struct tick_sched *tick_get_tick_sched(int cpu) #if defined(CONFIG_NO_HZ_COMMON) || defined(CONFIG_HIGH_RES_TIMERS) /* - * The time, when the last jiffy update happened. Protected by jiffies_lock. + * The time, when the last jiffy update happened. Write access must hold + * jiffies_lock and jiffies_seq. tick_nohz_next_event() needs to get a + * consistent view of jiffies and last_jiffies_update. */ static ktime_t last_jiffies_update; |