On 02/08/2017 18:36, Andres Oportus wrote: > +Paolo Bonzini > > On Mon, Jul 31, 2017 at 9:18 PM, Andres Oportus > <[email protected] <mailto:[email protected]>> wrote: > > commit 3d89e5478bf550a50c99e93adf659369798263b0 upstream.
Not an easy call because this is a guest patch that depends on a host patch. But since it is a corner case (CPU hotplug) and it was backported to 4.7 already, Acked-by: Paolo Bonzini <[email protected]> Paolo > Commit: > > e9532e69b8d1 ("sched/cputime: Fix steal time accounting vs. CPU > hotplug") > > ... set rq->prev_* to 0 after a CPU hotplug comes back, in order to > fix the case where (after CPU hotplug) steal time is smaller than > rq->prev_steal_time. > > However, this should never happen. Steal time was only smaller > because of the > KVM-specific bug fixed by the previous patch. Worse, the previous patch > triggers a bug on CPU hot-unplug/plug operation: because > rq->prev_steal_time is cleared, all of the CPU's past steal time will be > accounted again on hot-plug. > > Since the root cause has been fixed, we can just revert > commit e9532e69b8d1 ("sched/cputime: Fix steal time accounting vs. > CPU hotplug"). > > Signed-off-by: Wanpeng Li <[email protected] > <mailto:[email protected]>> > Signed-off-by: Peter Zijlstra (Intel) <[email protected] > <mailto:[email protected]>> > Acked-by: Paolo Bonzini <[email protected] > <mailto:[email protected]>> > Cc: Frederic Weisbecker <[email protected] <mailto:[email protected]>> > Cc: Linus Torvalds <[email protected] > <mailto:[email protected]>> > Cc: Mike Galbraith <[email protected] <mailto:[email protected]>> > Cc: Peter Zijlstra <[email protected] <mailto:[email protected]>> > Cc: Radim Krčmář <[email protected] <mailto:[email protected]>> > Cc: Rik van Riel <[email protected] <mailto:[email protected]>> > Cc: Thomas Gleixner <[email protected] <mailto:[email protected]>> > Fixes: 'commit e9532e69b8d1 ("sched/cputime: Fix steal time > accounting vs. CPU hotplug")' > Link: > > http://lkml.kernel.org/r/[email protected] > > <http://lkml.kernel.org/r/[email protected]> > Signed-off-by: Ingo Molnar <[email protected] <mailto:[email protected]>> > Signed-off-by: Greg Kroah-Hartman <[email protected] > <mailto:[email protected]>> > Signed-off-by: Andres Oportus <[email protected] > <mailto:[email protected]>> > --- > kernel/sched/core.c | 1 - > kernel/sched/sched.h | 13 ------------- > 2 files changed, 14 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index c436426..b103b9c 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -5553,7 +5553,6 @@ migration_call(struct notifier_block *nfb, > unsigned long action, void *hcpu) > > case CPU_UP_PREPARE: > rq->calc_load_update = calc_load_update; > - account_reset_rq(rq); > break; > > case CPU_ONLINE: > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index 4e5db65..55d92a1 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -1770,16 +1770,3 @@ static inline u64 irq_time_read(int cpu) > } > #endif /* CONFIG_64BIT */ > #endif /* CONFIG_IRQ_TIME_ACCOUNTING */ > - > -static inline void account_reset_rq(struct rq *rq) > -{ > -#ifdef CONFIG_IRQ_TIME_ACCOUNTING > - rq->prev_irq_time = 0; > -#endif > -#ifdef CONFIG_PARAVIRT > - rq->prev_steal_time = 0; > -#endif > -#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING > - rq->prev_steal_time_rq = 0; > -#endif > -} > -- > 1.9.1 > >
