Re: [PATCH 1/2] schedule: fix TASK_WAKEKILL vs SIGKILL race

[Matthew Wilcox <matthew@wil.cx>]

On Wed, Jun 04, 2008 at 10:01:01PM +0400, Oleg Nesterov wrote:
> > In my opinion, not checking for TASK_STOPPED or TASK_TRACED previously was
> > an oversight.  This should be fixed.
> 
> Perhaps, and the changelog has a special note. But imho we need another patch
> for that, this is a user-visible change.

It is?

> > >  	if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
> > > -		if (unlikely((prev->state & TASK_INTERRUPTIBLE) &&
> > > -				signal_pending(prev))) {
> > > +		if (unlikely(signal_pending_state(prev->state, prev)))
> > >  			prev->state = TASK_RUNNING;
> > > -		} else {
> > > +		else
> > >  			deactivate_task(rq, prev, 1);
> > > -		}
> > 
> > Getting rid of the extra braces is against CodingStyle:
> > 
> 
> With this patch the code is
> 
> 		if (unlikely(signal_pending_state(prev->state, prev)))
> 			prev->state = TASK_RUNNING;
> 		else
> 			deactivate_task(rq, prev, 1);

Didn't notice that.  Still, adjusting brace style is a bad idea.  Just
leave it the way it is.

> > This patch is going to add quite a few cycles to schedule().  Has anyone
> > done any benchmarks with a schedule-heavy workload?
> 
> No, I didn't. This patch is bugfix.

But there are other ways to fix the bug if this patch proves to be too
heavy-weight.

> However, I think the new helper can have other users. Not that I have a strong
> opinion.

I don't think so ...

-- 
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"Bill, look, we understand that you're interested in selling us this
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