On 02/08/2017 18:36, Andres Oportus wrote:
> +Paolo Bonzini
>
> On Mon, Jul 31, 2017 at 9:18 PM, Andres Oportus
> <andresopor...@android.com <mailto:andresopor...@android.com>> 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 <pbonz...@redhat.com>
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 <wanpeng...@hotmail.com
> <mailto:wanpeng...@hotmail.com>>
> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org
> <mailto:pet...@infradead.org>>
> Acked-by: Paolo Bonzini <pbonz...@redhat.com
> <mailto:pbonz...@redhat.com>>
> Cc: Frederic Weisbecker <fweis...@gmail.com <mailto:fweis...@gmail.com>>
> Cc: Linus Torvalds <torva...@linux-foundation.org
> <mailto:torva...@linux-foundation.org>>
> Cc: Mike Galbraith <efa...@gmx.de <mailto:efa...@gmx.de>>
> Cc: Peter Zijlstra <pet...@infradead.org <mailto:pet...@infradead.org>>
> Cc: Radim Krčmář <rkrc...@redhat.com <mailto:rkrc...@redhat.com>>
> Cc: Rik van Riel <r...@redhat.com <mailto:r...@redhat.com>>
> Cc: Thomas Gleixner <t...@linutronix.de <mailto:t...@linutronix.de>>
> Fixes: 'commit e9532e69b8d1 ("sched/cputime: Fix steal time
> accounting vs. CPU hotplug")'
> Link:
>
> http://lkml.kernel.org/r/1465813966-3116-3-git-send-email-wanpeng...@hotmail.com
>
> <http://lkml.kernel.org/r/1465813966-3116-3-git-send-email-wanpeng...@hotmail.com>
> Signed-off-by: Ingo Molnar <mi...@kernel.org <mailto:mi...@kernel.org>>
> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org
> <mailto:gre...@linuxfoundation.org>>
> Signed-off-by: Andres Oportus <andresopor...@google.com
> <mailto:andresopor...@google.com>>
> ---
> 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
>
>
