linux-kernel - Re: [PATCH 4/2] perf_counter: Fix swcounter context invariance

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20090813082900.GB6001@nowhere>
Date:	Thu, 13 Aug 2009 10:29:01 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Paul Mackerras <paulus@...ba.org>,
	stephane eranian <eranian@...glemail.com>,
	Corey J Ashford <cjashfor@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/2] perf_counter: Fix swcounter context invariance

On Thu, Aug 13, 2009 at 10:22:58AM +0200, Peter Zijlstra wrote:
> On Thu, 2009-08-13 at 10:05 +0200, Frederic Weisbecker wrote:
> > On Thu, Aug 13, 2009 at 09:51:55AM +0200, Peter Zijlstra wrote:
> > > Not really related to this topic, but it needs posting anyway.
> > > 
> > > ---
> > > 
> > > Subject: perf_counter: Fix swcounter context invariance
> > > From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> > > Date: Fri Aug 07 13:29:13 CEST 2009
> > > 
> > > perf_swcounter_is_counting() uses a lock, which means we cannot use
> > > swcounters from NMI or when holding that particular lock, this is
> > > unintended.
> > > 
> > > The below removes the lock, this opens up race window, but not worse
> > > than the swcounters already experience due to RCU traversal of the
> > > context in perf_swcounter_ctx_event().
> > > 
> > > Cc: Paul Mackerras <paulus@...ba.org>
> > > Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> > 
> > 
> > 
> > As a side effect, it's possible this also fixes the hard lockups
> > while opening a lockdep tracepoint counter.
> 
> It will -- not a side-effect at all, intended consequence :-)


Great then! Important fix for .31 :-)

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/