linux-kernel - Re: [PATCH 22/38] tick-sched: no need to recheck cpu_online() in can_stop_idle

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Message-ID: <534C3C65.1030808@codeaurora.org>
Date:	Mon, 14 Apr 2014 12:52:05 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>, tglx@...utronix.de
CC:	linaro-kernel@...ts.linaro.org, linux-kernel@...r.kernel.org,
	fweisbec@...il.com, Arvind.Chauhan@....com,
	linaro-networking@...aro.org
Subject: Re: [PATCH 22/38] tick-sched: no need to recheck cpu_online() in
 can_stop_idle_tick()

On 04/14/14 09:23, Viresh Kumar wrote:
> We have already checked if 'cpu' is online or not and so don't need to recheck
> it.
>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>

Hm... doing some git archeology shows fa116ea35ec7 (nohz: no softirq
pending warnings for offline cpus, 2008-12-11), where the cpu_online()
check was added. Before that commit we already checked cpu_online()
similar to how the code is today. Perhaps we need to add a comment here?

> ---
>  kernel/time/tick-sched.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
> index 9cbba513..c81b6cf 100644
> --- a/kernel/time/tick-sched.c
> +++ b/kernel/time/tick-sched.c
> @@ -716,7 +716,7 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
>  	if (need_resched())
>  		return false;
>  
> -	if (unlikely(local_softirq_pending() && cpu_online(cpu))) {
> +	if (unlikely(local_softirq_pending())) {
>  		static int ratelimit;
>  
>  		if (ratelimit < 10 &&


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