linux-kernel - Re: lockdep trace from posix timers

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Message-ID: <1345477609.23018.61.camel@twins>
Date:	Mon, 20 Aug 2012 17:46:49 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	rostedt <rostedt@...dmis.org>, dhowells <dhowells@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: lockdep trace from posix timers

On Mon, 2012-08-20 at 17:32 +0200, Oleg Nesterov wrote:

> > I guess we could steal the entire list and requeue it afterwards and
> > lift TIF_NOTIFY_RESUME along with it..
> 
> We can't. This can race with exit_task_work(). And this can break
> fput(), the task can return to the userspace without __fput().

So we could put that spinlock back around cancel and run and leave add
lockless. That'd solve my immediate problem but its not something I'm
proud of.

All schemes I can come up with end up being broken or effectively the
same as the above proposal.
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