From: Steven Rostedt <rostedt@goodmis.org>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Fengguang Wu <fengguang.wu@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
john stultz <johnstul@us.ibm.com>, Ingo Molnar <mingo@elte.hu>,
LKML <linux-kernel@vger.kernel.org>,
"Paul E. McKenney" <paulmck@us.ibm.com>
Subject: Re: lockdep WARNING for run_timer_softirq()
Date: Wed, 05 Sep 2012 15:23:48 -0400 [thread overview]
Message-ID: <1346873028.27919.70.camel@gandalf.local.home> (raw)
In-Reply-To: <1346865555.2600.38.camel@twins>
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.
between:
lockdep_softirq_exit();
and
__local_bh_enable(SOFTIRQ_OFFSET);
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.
-- Steve
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]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1346873028.27919.70.camel@gandalf.local.home \
--to=rostedt@goodmis.org \
--cc=a.p.zijlstra@chello.nl \
--cc=fengguang.wu@intel.com \
--cc=johnstul@us.ibm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=paulmck@us.ibm.com \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).