Re: [PATCH] sched: correct how RT task is picked

From: Hillf Danton
Date: Wed May 18 2011 - 10:46:24 EST

On Wed, May 18, 2011 at 9:24 PM, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> On Wed, 2011-05-18 at 21:19 +0800, Hillf Danton wrote:
>> Hi all
>> The patch is prepared again, in which tests for both cpu and
>> nr_cpus_allowed are dropped.
>> The reason to drop nr_cpus_allowed is to make sure that the
>> returned value is correct for both case that cpu == rq->cpu and
>> case that cpu != rq->cpu.
> Why would we pick a task that can't migrate?
Hi Steven

For migration, it is the case that cpu != rq->cpu, and
if cpu is allowed by task's affinity, it is bug that task
could not goto cpu because of nr_cpus_allowed since
the nr_cpus_allowed is computed based on the cpus_allowed mask.

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