linux-kernel - Re: BUG: spinlock bad magic on CPU#0, migration/0/9

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Message-ID: <20150212193905.GB28499@redhat.com>
Date:	Thu, 12 Feb 2015 20:39:05 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Nicholas Mc Guire <der.herr@...r.at>
Cc:	Davidlohr Bueso <dave@...olabs.net>, paulmck@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org, waiman.long@...com,
	peterz@...radead.org, raghavendra.kt@...ux.vnet.ibm.com
Subject: Re: BUG: spinlock bad magic on CPU#0, migration/0/9

On 02/12, Nicholas Mc Guire wrote:
>
> On Thu, 12 Feb 2015, Oleg Nesterov wrote:
>
> > --- x/kernel/sched/completion.c
> > +++ x/kernel/sched/completion.c
> > @@ -274,7 +274,7 @@ bool try_wait_for_completion(struct comp
> >  	 * first without taking the lock so we can
> >  	 * return early in the blocking case.
> >  	 */
> > -	if (!ACCESS_ONCE(x->done))
> > +	if (!READ_ONCE(x->done))
> >  		return 0;
> >
> from looking at compiler.h I don't think that there would be a difference
> between ACCESS_ONCE() and READ_ONCE() in this case

Yes, this is unrelated "while at it" cosmetic change, now that we have
READ_ONCE() it makes more sense in this case.

Oleg.

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