linux-kernel - Re: [PATCH/RFC] timer: fix deadlock on cpu hotplug

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Message-ID: <1285373987.2275.1048.camel@laptop>
Date:	Sat, 25 Sep 2010 02:19:47 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
Cc:	Tejun Heo <tj@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH/RFC] timer: fix deadlock on cpu hotplug

On Thu, 2010-09-23 at 15:31 +0200, Heiko Carstens wrote:
> On Wed, Sep 22, 2010 at 04:29:36PM +0200, Peter Zijlstra wrote:
> > On Wed, 2010-09-22 at 11:22 +0200, Peter Zijlstra wrote:
> > 
> > > The idea was to move it to a class of its own above SCHED_FIFO.
> > > 
> > > I'll try and get something done, but I'm heading out to LinuxCon.JP
> > > soon.
> > 
> > Something like the below, it seems to boot, build a kernel and hotplug.
> 
> Thanks for the fast patch. Yes, it works. Sort of:
> 
> ------------[ cut here ]------------

<SPLAT>

> 
> ..and crashes afterwards ;)

Yeah, I can imagine,. weird though, kthread_create() should leave the
new thread in uninterruptible context. The above warning implies this is
not so.. 

> Btw. I also tried to boot 2.6.35.5 with your patch and it hangs just at
> the beginning. I also had to apply 5e3d20a68f63fc5a310687d81956c3b96e488b84
> "init: Remove the BKL from startup code" to make the machine boot again,
> which was a bit surprising.

Most curious and unexpected,.. I'll try and have a look, but it might
have to wait until after LinuxCon.JP..


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