From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Ari Savolainen <ari.m.savolainen@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@elte.hu>,
Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] perf: Fix RCU dereference check in perf_event_comm
Date: Thu, 22 Mar 2012 10:53:16 +0100 [thread overview]
Message-ID: <1332409996.18960.511.camel@twins> (raw)
In-Reply-To: <CAEbykaXUy7HEyW7mBaTNmB94NwyjuJBbA1R-H49Jjk5M-iL_fw@mail.gmail.com>
On Thu, 2012-03-22 at 01:43 +0200, Ari Savolainen wrote:
> The warning below is printed when executing a command like
> sudo perf record su - user -c "echo hello"
>
> It's fixed by moving the call of perf_event_comm to be protected
> by the task lock.
That seems like a rather poor solution since it increases the lock hold
time for no explained reason.
> include/linux/cgroup.h:567 suspicious rcu_dereference_check() usage!
> [<ffffffff8109be55>] lockdep_rcu_suspicious+0xe5/0x100
> [<ffffffff811131fa>] perf_event_comm+0x37a/0x4d0
So where exactly is this, perf_event_comm_event() takes rcu_read_lock()
so I presume its before that.
next prev parent reply other threads:[~2012-03-22 9:53 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-21 23:43 [PATCH] perf: Fix RCU dereference check in perf_event_comm Ari Savolainen
2012-03-22 9:53 ` Peter Zijlstra [this message]
2012-03-22 11:36 ` Ari Savolainen
2012-03-26 12:41 ` Peter Zijlstra
2012-04-26 15:06 ` Stephane Eranian
2012-04-29 20:07 ` Ari Savolainen
2012-05-18 16:38 ` Stephane Eranian
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