linux-kernel - Re: [PATCH 2/2] sched: Add a check for cpu unbound deferrable timers

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Date:   Mon, 16 Mar 2020 09:38:45 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Prasad Sodagudi <psodagud@...eaurora.org>, john.stultz@...aro.org,
        sboyd@...nel.org
Cc:     linux-kernel@...r.kernel.org, saravanak@...gle.com,
        tsoni@...eaurora.org, tj@...nel.org,
        Prasad Sodagudi <psodagud@...eaurora.org>
Subject: Re: [PATCH 2/2] sched: Add a check for cpu unbound deferrable timers

Prasad Sodagudi <psodagud@...eaurora.org> writes:
> @@ -948,6 +949,11 @@ static void __tick_nohz_idle_stop_tick(struct tick_sched *ts)
>  	ktime_t expires;
>  	int cpu = smp_processor_id();
>  
> +#ifdef CONFIG_SMP
> +	if (check_pending_deferrable_timers(cpu))
> +		raise_softirq_irqoff(TIMER_SOFTIRQ);
> +#endif

So if that raises the soft interrupt then the warning in 

can_stop_idle_tick()

	if (unlikely(local_softirq_pending())) {
		....
                pr_warn()

will trigger. Try again.

Thanks,

        tglx