Messages in this thread Patch in this message | | | Date | Tue, 17 Nov 2020 14:19:44 +0100 | From | Thomas Gleixner <> | Subject | [patch 2/7] tick: Document protections for tick related data |
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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> --- kernel/time/tick-common.c | 4 +++- kernel/time/tick-sched.c | 4 +++- 2 files changed, 6 insertions(+), 2 deletions(-)
--- 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; --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -44,7 +44,9 @@ struct tick_sched *tick_get_tick_sched(i #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;
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