linux-kernel - Re: [PATCH] sched/deadline: No need to check NULL later

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Date:	Fri, 1 Apr 2016 20:16:37 +0800
From:	Xunlei Pang <xpang@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, Juri Lelli <juri.lelli@....com>,
	Ingo Molnar <mingo@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] sched/deadline: No need to check NULL later_mask

On 2016/04/01 at 19:29, Peter Zijlstra wrote:
> On Fri, Apr 01, 2016 at 07:13:18PM +0800, Xunlei Pang wrote:
>> Unlike rt tasks, we (should) have no deadline tasks in
>> booting phase before the mask is allocated, so we can
>> safely remove the check.
> Why? And have the kernel explode once it grows an early deadline task?
>
> Is there _any_ benefit to this?

This is a performance-critical path, it'd be better to avoid such a check.

I think in the early boot stage before sched_init_smp(), it's weird to
use a deadline task, relying on rt tasks should be enough for us.

Please ignore it if you don't think so :-)

Regards,
Xunlei