netdev - Re: [PATCH] netpoll: Fix carrier detection for drivers that are using phylib

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Date:	Thu, 09 Jul 2009 09:43:00 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Anton Vorontsov <avorontsov@...mvista.com>,
	Andrew Morton <akpm@...ux-foundation.org>, oleg@...hat.com,
	mingo@...e.hu, linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] netpoll: Fix carrier detection for drivers that are
 using phylib

On Thu, 2009-07-09 at 16:31 +0200, Peter Zijlstra wrote:
> On Thu, 2009-07-09 at 09:18 -0500, Matt Mackall wrote:
> > 
> > Sorry if I was unclear. I'm suggesting setting the count so the existing
> > PREEMPT_ACTIVE test here fires:
> > 
> > int __sched _cond_resched(void)
> > {
> >         if (need_resched() && !(preempt_count() & PREEMPT_ACTIVE) &&
> >                                         system_state == SYSTEM_RUNNING) {
> >                 __cond_resched();
> >                 return 1;
> >         }
> >         return 0;
> > }
> 
> Right, /me read preempt and thought a simple preempt inc but didn't read
> the code. Shame on me.
> 
> So something like (utterly untested and such)

Yeah, that's what I had in mind. Probably throw in a define:

/* for disabling scheduling in early boot */
#define PREEMPT_EARLY (1 + PREEMPT_ACTIVE)

and slap a comment on the sub_preempt_count().

Does anything actually use scheduler_running yet? Perhaps my tree is
old.

Also, might_sleep's use of system_state probably bears revisiting.

-- 
http://selenic.com : development and support for Mercurial and Linux


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