From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755389Ab1KWRdU (ORCPT ); Wed, 23 Nov 2011 12:33:20 -0500 Received: from mail-vw0-f46.google.com ([209.85.212.46]:63350 "EHLO mail-vw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752360Ab1KWRdT (ORCPT ); Wed, 23 Nov 2011 12:33:19 -0500 Date: Wed, 23 Nov 2011 09:33:13 -0800 From: Tejun Heo To: Steven Rostedt Cc: Frederic Weisbecker , Ingo Molnar , Jiri Olsa , linux-kernel@vger.kernel.org, "Paul E. McKenney" Subject: Re: [PATCH 1/2] trace_events_filter: use rcu_assign_pointer() when setting ftrace_event_call->filter Message-ID: <20111123173313.GB29639@google.com> References: <20111123014603.GA19630@google.com> <1322061407.20742.51.camel@frodo> <20111123160653.GB25780@google.com> <1322068000.20742.61.camel@frodo> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1322068000.20742.61.camel@frodo> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Steven. On Wed, Nov 23, 2011 at 12:06:40PM -0500, Steven Rostedt wrote: > > So, synchronized_sched() being called after isn't relevant. We want > > smp_wmb() between data structure initialization and assignment of the > > new pointer. > > Ah, you're saying that we need to guarantee that the allocated filter is > seen before we update the call->filter to point to it. OK, fair enough, > this does look like a bug fix. > > Is it big enough to be considered for stable? It's unlikely to happen for x86 or arm and that probably is the biggest reason there hasn't already been a bug report. It isn't very urgent but at the same time the change is almost trivial, so marking it for stable is a pretty safe bet. I lean toward marking it for stable but the leaning isn't too strong. :) Thanks. -- tejun