Commit-ID: cab245d68c38afff1a4c4d018ab7e1d316982f5d Gitweb: http://git.kernel.org/tip/cab245d68c38afff1a4c4d018ab7e1d316982f5d Author: Frederic Weisbecker <fweisbec@xxxxxxxxx> AuthorDate: Thu, 19 Nov 2015 16:47:31 +0100 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Fri, 4 Dec 2015 10:34:44 +0100 sched/cputime: Correctly handle task guest time on housekeepers When a task runs on a housekeeper (a CPU running with the periodic tick with neighbours running tickless), it doesn't account cputime using vtime but relies on the tick. Such a task has its vtime_snap_whence value set to VTIME_INACTIVE. Readers won't handle that correctly though. As long as vtime is running on some CPU, readers incorretly assume that vtime runs on all CPUs and always compute the tickless cputime delta, which is only junk on housekeepers. So lets fix this with checking that the target runs on a vtime CPU through the appropriate state check before computing the tickless delta. Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Cc: Chris Metcalf <cmetcalf@xxxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: Hiroshi Shimamoto <h-shimamoto@xxxxxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Luiz Capitulino <lcapitulino@xxxxxxxxxx> Cc: Mike Galbraith <efault@xxxxxx> Cc: Paul E . McKenney <paulmck@xxxxxxxxxxxxxxxxxx> Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/1447948054-28668-5-git-send-email-fweisbec@xxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- kernel/sched/cputime.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 4a18a6e..5cf24e7 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -795,7 +795,7 @@ cputime_t task_gtime(struct task_struct *t) seq = read_seqbegin(&t->vtime_seqlock); gtime = t->gtime; - if (t->flags & PF_VCPU) + if (t->vtime_snap_whence == VTIME_SYS && t->flags & PF_VCPU) gtime += vtime_delta(t); } while (read_seqretry(&t->vtime_seqlock, seq)); -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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