linux-kernel - Re: [PATCH] sched/rt: silence double clock update warning by using rq

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Message-ID: <f094734a-eeae-02db-dd0b-d7fe7e9d5db8@arm.com>
Date:   Thu, 15 Aug 2019 18:24:54 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     Phil Auld <pauld@...hat.com>, linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>
Subject: Re: [PATCH] sched/rt: silence double clock update warning by using
 rq_lock wrappers

On 15/08/2019 15:53, Phil Auld wrote:
> With WARN_DOUBLE_CLOCK enabled a false positive warning can occur in rt
> 
>         [] rq->clock_update_flags & RQCF_UPDATED
>         [] WARNING: CPU: 6 PID: 21426 at kernel/sched/core.c:225 
> 						update_rq_clock+0x90/0x130
>           [] Call Trace:
>           []  update_rq_clock+0x90/0x130
>           []  sched_rt_period_timer+0x11f/0x340
>           []  __hrtimer_run_queues+0x100/0x280
>           []  hrtimer_interrupt+0x100/0x220
>           []  smp_apic_timer_interrupt+0x6a/0x130
>           []  apic_timer_interrupt+0xf/0x20
> 
> sched_rt_period_timer does:
>                 raw_spin_lock(&rq->lock);
>                 update_rq_clock(rq);
> 
> which triggers the warning because of not using the rq_lock wrappers.
> So, use the wrappers.
> 
> Signed-off-by: Phil Auld <pauld@...hat.com>
> Cc: Peter Zijlstra (Intel) <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Valentin Schneider <valentin.schneider@....com>
> Cc: Dietmar Eggemann <dietmar.eggemann@....com>

Looks sane to me, and no missing _irqsave this time around ;)

Reviewed-by: Valentin Schneider <valentin.schneider@....com>