Locking the seqcount on idle vtime accounting wasn't thought to be necessary because the readers of idle cputime don't use vtime (yet).
Now updating vtime expect the related seqcount to be locked so do it for locking coherency purposes. Also idle cputime updates use vtime, but idle cputime readers use the traditional ad-hoc nohz time delta. We may want to consider moving readers to use vtime to consolidate the overall accounting scheme. The seqcount will be a functional requirement for it. Signed-off-by: Frederic Weisbecker <[email protected]> Cc: Yauheni Kaliuta <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Wanpeng Li <[email protected]> Cc: Ingo Molnar <[email protected]> --- kernel/sched/cputime.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 54eb945..6e74ec2 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -800,7 +800,11 @@ EXPORT_SYMBOL_GPL(vtime_guest_exit); void vtime_account_idle(struct task_struct *tsk) { + struct vtime *vtime = &tsk->vtime; + + write_seqcount_begin(&vtime->seqcount); account_idle_time(get_vtime_delta(&tsk->vtime)); + write_seqcount_end(&vtime->seqcount); } void arch_vtime_task_switch(struct task_struct *prev) -- 2.7.4
