linux-kernel - Re: [PATCH RESEND v10] sched/deadline: support dl task migration during cpu hotplug

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Date:	Tue, 17 Mar 2015 07:01:10 +0800
From:	Wanpeng Li <wanpeng.li@...ux.intel.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@....com>, linux-kernel@...r.kernel.org,
	Wanpeng Li <wanpeng.li@...ux.intel.com>
Subject: Re: [PATCH RESEND v10] sched/deadline: support dl task migration
 during cpu hotplug

Hi Ingo,
On Mon, Mar 16, 2015 at 04:01:02PM +0100, Ingo Molnar wrote:
>> +
>> +			/*
>> +			 * If cannot preempt any rq, fallback to pick any
>> +			 * online cpu.
>
>s/If cannot/If we cannot
>s/fallback/fall back

Will do.

>
>> +			 */
>> +			fallback = true;
>> +			cpu = cpumask_any_and(cpu_active_mask,
>> +						tsk_cpus_allowed(p));
>
>shouldn't be on separate lines - but this is also a sign that the guts 

Otherwise there is a "WARNING: line over 80 characters".

>of this new code should be in a helper function, not inside several 
>layers of branches.

Do you mean the whole patch should be in a helper function?

>
>> +			if (cpu >= nr_cpu_ids) {
>> +				if (dl_bandwidth_enabled()) {
>> +					/*
>> +					 * Fail to find any suitable cpu.
>> +					 * The task will never come back!
>> +					 */
>> +					WARN_ON(1);
>
>Can this condition happen to users with a non-buggy kernel?

What do you prefer? ;-)

Regards,
Wanpeng Li

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