The following commit has been merged into the timers/core branch of tip: Commit-ID: c398960cd82b233886fbff163986f998b5a5c008 Gitweb: https://git.kernel.org/tip/c398960cd82b233886fbff163986f998b5a5c008 Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> AuthorDate: Tue, 17 Nov 2020 14:19:44 +01:00 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitterDate: Thu, 19 Nov 2020 10:48:28 +01:00 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@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20201117132006.197713794@xxxxxxxxxxxxx --- kernel/time/tick-common.c | 4 +++- 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 6c9c342..68504eb 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 81632cd..15360e6 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;
|