Date: Fri, 25 Nov 2005 21:14:54 -0800
From: "Paul E. McKenney" <paulmck@us.ibm.com>
To: Wu Fengguang <wfg@mail.ustc.edu.cn>, linux-kernel@vger.kernel.org,
       Andrew Morton <akpm@osdl.org>, mingo@elte.hu, levon@movementarian.org
Subject: Re: BUG: spinlock recursion on 2.6.14-mm2 when oprofiling
Message-ID: <20051126051454.GA3104@us.ibm.com>
Reply-To: paulmck@us.ibm.com
References: <20051118152101.GA4690@mail.ustc.edu.cn> <20051125220117.GA1836@us.ibm.com> <20051125232829.GA2405@us.ibm.com> <20051126033955.GC7226@mail.ustc.edu.cn>
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On Sat, Nov 26, 2005 at 11:39:55AM +0800, Wu Fengguang wrote:
> On Fri, Nov 25, 2005 at 03:28:29PM -0800, Paul E. McKenney wrote:
> > And here is an alternative patch that assumes that the answer to both
> > questions above is "no".  It is shorter, though mostly due to use of
> > the list_splice_init() and list_for_each_entry_safe() primitives.
> 
> Ok, I'll try it. But it may take time.
> 
> Currently I'm running oprofile on linux-2.6.15-rc2-mm1. It seems the bug is not
> quite reproducible. I'll report again if there are any new findings.

Yep, the bug is indeed non-deterministic.  For it to happen, softirq
must interrupt a "task_mortuary" critical section, and that softirq
must execute a task-struct RCU callback.

						Thanx, Paul
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