linux-kernel - Re: [PATCH] jump_label_inc may return before the code is patched

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Message-ID: <1320248542.4793.34.camel@gandalf.stny.rr.com>
Date:	Wed, 02 Nov 2011 11:42:22 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Gleb Natapov <gleb@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Jason Baron <jbaron@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, mingo@...e.hu
Subject: Re: [PATCH] jump_label_inc may return before the code is patched

On Wed, 2011-11-02 at 17:21 +0200, Gleb Natapov wrote:
> On Tue, Oct 18, 2011 at 05:06:25PM -0400, Steven Rostedt wrote:
> > On Tue, 2011-10-18 at 19:55 +0200, Gleb Natapov wrote:
> > > If cpu A calls jump_label_inc() just after atomic_add_return() is
> > > called by cpu B, atomic_inc_not_zero() will return value greater then
> > > zero and jump_label_inc() will return to a caller before jump_label_update()
> > > finishes its job on cpu B.
> > 
> > OK, I see what you are saying. There's a race here that jump_label_inc
> > may return before jump labels are actually activated. I have no issue
> > with this change. This guarantees that jump labels will be active on
> > return of jump_label_inc().
> > 
> > I'm assuming that jump_label_update() does memory barries, as it does
> > modify code, and would be itself a synchronization point.
> > 
> > Acked-by: Steven Rostedt <rostedt@...dmis.org>
> > 
> So through what tree this should go to Linus' git?

I'll pull it in. I'm currently scrambling around getting back up to
speed after a 11 day conference spree.



-- Steve


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