From: Steven Rostedt <email@example.com>
To: Peter Zijlstra <firstname.lastname@example.org>
Cc: Fengguang Wu <email@example.com>,
Thomas Gleixner <firstname.lastname@example.org>,
john stultz <email@example.com>, Ingo Molnar <firstname.lastname@example.org>,
"Paul E. McKenney" <email@example.com>
Subject: Re: lockdep WARNING for run_timer_softirq()
Date: Wed, 05 Sep 2012 15:23:48 -0400 [thread overview]
Message-ID: <firstname.lastname@example.org> (raw)
On Wed, 2012-09-05 at 19:19 +0200, Peter Zijlstra wrote:
> On Wed, 2012-09-05 at 13:14 -0400, Steven Rostedt wrote:
> > This looks very familiar to Fengguang's previous bug report. I can't
> > seem to find it on LKML.org. Probably because of the two attachments
> > (dmesg and config) caused lkml to nuke it.
> > I'll forward it to you.
> Yuck that looks like fun too.. doesn't look like the if() thing though.
I'm able to trigger a similar bug too. And this is what I've found.
the __local_bh_enable() is being traced, which means we call the
ftrace_ops_list_func() (which is called instead of the direct function
in some configs). This does a:
op = rcu_dereference_raw(ftrace_ops_list);
where rcu_dereference_raw() eventually calls rcu_read_lock_held() which
calls lock_is_held(), and this does the consistency checks, where
lockdep thinks we are no longer in the softirq, but we haven't gotten to
the point in __local_bh_enable() where the preempt_count is decremented
to state this.
But this doesn't look the same as the branch tracer. I'll continue
looking into that one.
prev parent reply other threads:[~2012-09-05 19:23 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-31 7:21 lockdep WARNING for run_timer_softirq() Fengguang Wu
2012-08-31 7:32 ` Fengguang Wu
2012-09-05 11:47 ` Peter Zijlstra
2012-09-05 14:20 ` Steven Rostedt
2012-09-05 17:09 ` Peter Zijlstra
2012-09-05 17:14 ` Steven Rostedt
2012-09-05 17:19 ` Peter Zijlstra
2012-09-05 19:23 ` Steven Rostedt [this message]
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