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From: Robert Love <rml@tech9.net>
To: Joe Korty <joe.korty@ccur.com>
Cc: Andrew Morton <akpm@digeo.com>,
	Alan Cox <alan@lxorguk.ukuu.org.uk>,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC] 2.5 TASK_INTERRUPTIBLE preemption race
Date: 14 Apr 2003 18:00:42 -0400	[thread overview]
Message-ID: <1050357642.3664.89.camel@localhost> (raw)
In-Reply-To: <20030414215410.GA18922@rudolph.ccur.com>

On Mon, 2003-04-14 at 17:54, Joe Korty wrote:

> Is this analysis correct?  If it is, perhaps there is an alternative
> to fixing these cases individually: make the TASK_INTERRUPTIBLE/
> TASK_UNINTERRUPTIBLE states block preemption.  In which case the
> 'set_current_state(TASK_RUNNING)' macro would need to include the
> same preemption check as 'preemption_enable'.

Thankfully you are wrong or we would have some serious problems :)

See kernel/sched.c :: preempt_schedule() where we set p->preempt_count
to PREEMPT_ACTIVE.

Then see kernel/sched.c :: schedule() where we short-circuit the
remove-from-runqueue code if PREEMPT_ACTIVE is set.

Thus, it is safe to preempt regardless of the task's state.  It will
eventually reschedule.

	Robert Love


  reply	other threads:[~2003-04-14 21:50 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-04-14 21:54 [RFC] 2.5 TASK_INTERRUPTIBLE preemption race Joe Korty
2003-04-14 22:00 ` Robert Love [this message]
2003-04-14 22:27   ` Joe Korty
2003-04-14 22:30     ` Robert Love

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