diff options
| author | Jens Axboe <axboe@kernel.dk> | 2013-12-31 09:51:02 -0700 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2013-12-31 09:51:02 -0700 |
| commit | b28bc9b38c52f63f43e3fd875af982f2240a2859 (patch) | |
| tree | 76cdb7b52b58f5685993cc15ed81d1c903023358 /kernel/time/tick-common.c | |
| parent | 8d30726912cb39c3a3ebde06214d54861f8fdde2 (diff) | |
| parent | 802eee95bde72fd0cd0f3a5b2098375a487d1eda (diff) | |
Merge tag 'v3.13-rc6' into for-3.14/core
Needed to bring blk-mq uptodate, since changes have been going in
since for-3.14/core was established.
Fixup merge issues related to the immutable biovec changes.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Conflicts:
block/blk-flush.c
fs/btrfs/check-integrity.c
fs/btrfs/extent_io.c
fs/btrfs/scrub.c
fs/logfs/dev_bdev.c
Diffstat (limited to 'kernel/time/tick-common.c')
| -rw-r--r-- | kernel/time/tick-common.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c index 64522ecdfe0e..162b03ab0ad2 100644 --- a/kernel/time/tick-common.c +++ b/kernel/time/tick-common.c @@ -33,6 +33,21 @@ DEFINE_PER_CPU(struct tick_device, tick_cpu_device); */ ktime_t tick_next_period; ktime_t tick_period; + +/* + * tick_do_timer_cpu is a timer core internal variable which holds the CPU NR + * which is responsible for calling do_timer(), i.e. the timekeeping stuff. This + * variable has two functions: + * + * 1) Prevent a thundering herd issue of a gazillion of CPUs trying to grab the + * timekeeping lock all at once. Only the CPU which is assigned to do the + * update is handling it. + * + * 2) Hand off the duty in the NOHZ idle case by setting the value to + * TICK_DO_TIMER_NONE, i.e. a non existing CPU. So the next cpu which looks + * at it will take over and keep the time keeping alive. The handover + * procedure also covers cpu hotplug. + */ int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT; /* |