linux-kernel - Re: s2r badness

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Message-Id: <1248115844.23509.0.camel@laptop>
Date:	Mon, 20 Jul 2009 20:50:44 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	prasad@...ux.vnet.ibm.com
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Len Brown <lenb@...nel.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	lkml <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: s2r badness

On Mon, 2009-07-20 at 23:50 +0530, K.Prasad wrote:

> > > [   74.576953] ------------[ cut here ]------------
> > > [   74.576953] WARNING: at /usr/src/linux-2.6/kernel/softirq.c:143 local_bh_enable_ip+0x8b/0xc0()
> > > [   74.576953] Hardware name: 2242CTO

> > > [   74.576953] Pid: 5406, comm: bash Not tainted 2.6.31-rc3-tip #32
> > > [   74.576953] Call Trace:
> > > [   74.576953]  [<ffffffff8107401b>] ? local_bh_enable_ip+0x8b/0xc0
> > > [   74.576953]  [<ffffffff8106c838>] warn_slowpath_common+0x78/0xd0
> > > [   74.576953]  [<ffffffff8106c89f>] warn_slowpath_null+0xf/0x20
> > > [   74.576953]  [<ffffffff8107401b>] local_bh_enable_ip+0x8b/0xc0
> > > [   74.576953]  [<ffffffff814d08d9>] _spin_unlock_bh+0x19/0x20
> > > [   74.576953]  [<ffffffff810d2c77>] load_debug_registers+0x67/0x80
> > 
> > That's the hw breakpoint support stuff which does the spin_unlock_bh
> > at a point where interrupts are disabled. So that's a -tip tree issue,
> > not mainline.
> >
> 
> load_debug_registers() uses spin_(un)lock_bh() and not a spin-lock() to
> protect itself from flush_thread_hw_breakpoint() [which is invoked in
> softIRQ context].
> 
> I'd like to recreate this traceback to investigate and fix this. What
> steps, when done cause this message to appear?

Close the lid and open it again?

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