linux-kernel - Re: [PATCH v2 0/6] stop_machine: cleanups, fix, remove lglock

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Message-ID: <20150730173416.GP25159@twins.programming.kicks-ass.net>
Date:	Thu, 30 Jul 2015 19:34:16 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ingo Molnar <mingo@...nel.org>, Rik van Riel <riel@...hat.com>,
	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/6] stop_machine: cleanups, fix, remove lglock

On Tue, Jul 21, 2015 at 09:22:19PM +0200, Oleg Nesterov wrote:
> Hello,
> 
> Let me resend this. The only change in v2 is that I rediffed this
> series against v4.2-rc3.
> 
> 5/6 patch fixes the bug, I think. Say, stop_one_cpu(X) can race with
> _cpu_down(X)->stop_machine() so that the kernel will crash if this
> CPU X becomes online again. The window after cpu_stopper_thread()
> returns and before smpboot_thread() calls ->park() is tiny, but still
> this is possible afaics. But see the changelog in 6/6, I think we
> should turn this cpu_stop_signal_done() into BUG() later.

These I've queued (from v1 I think, nothing really changed there).

> 6/6 removes lglock from kernel/stop_machine.c.
> 
> Peter, Rik, what do you think ?

This one I've got some 'problems' with, but let me reply there.
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