linux-kernel - Re: Q: wait_task_inactive() and !CONFIG_SMP && CONFIG

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Date:	Sun, 27 Jul 2008 13:05:51 -0700 (PDT)
From:	Roland McGrath <roland@...hat.com>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: Re: Q: wait_task_inactive() and !CONFIG_SMP && CONFIG_PREEMPT

> Without CONFIG_SMP wait_task_inactive() is noop, this doesn't look right.
> Shouldn't we also take CONFIG_PREEMPT into account?

wait_task_inactive is only called when task->state is nonzero (i.e. not
TASK_RUNNING).  Preemption leaves a task in TASK_RUNNING, so a preempted
task shouldn't ever be passed to wait_task_inactive.  I dont see the problem.

> Also, the !SMP version of wait_task_inactive() always returns 1, this
> doesn't conform to the comment near kernel/sched.c:wait_task_inactive().

You mean the "(its total switch count)" part of the comment?
The normative part was only meant to be "a positive number".


Thanks,
Roland
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