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Date:   Mon, 30 Jul 2018 14:41:01 +0200 (CEST)
From:   Thomas Gleixner <tglx@linutronix.de>
To:     Peter Zijlstra <peterz@infradead.org>
cc:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        isaacm@codeaurora.org, matt@codeblueprint.co.uk, mingo@kernel.org,
        linux-kernel@vger.kernel.org, psodagud@codeaurora.org,
        gregkh@linuxfoundation.org, pkondeti@codeaurora.org,
        stable@vger.kernel.org
Subject: Re: [PATCH] stop_machine: Disable preemption after queueing stopper
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In-Reply-To: <20180730112140.GH2494@hirez.programming.kicks-ass.net>
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 <20180730112140.GH2494@hirez.programming.kicks-ass.net>
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On Mon, 30 Jul 2018, Peter Zijlstra wrote:

> On Mon, Jul 30, 2018 at 12:20:57PM +0200, Thomas Gleixner wrote:
> > On Tue, 24 Jul 2018, Sebastian Andrzej Siewior wrote:
> > > On 2018-07-23 18:13:48 [-0700], isaacm@codeaurora.org wrote:
> > > > Hi all,
> > > Hi,
> > > 
> > > > Are there any comments about this patch?
> > > 
> > > I haven't look in detail at this but your new preempt_disable() makes
> > > things unbalanced for the err != 0 case.
> > 
> > It doesn't but that code is really an unreadable pile of ...
> 
> ---
> Subject: stop_machine: Reflow cpu_stop_queue_two_works()
> 
> The code flow in cpu_stop_queue_two_works() is a little arcane; fix
> this by lifting the preempt_disable() to the top to create more natural
> nesting wrt the spinlocks and make the wake_up_q() and preempt_enable()
> unconditional at the end.
> 
> Furthermore, enable preemption in the -EDEADLK case, such that we
> spin-wait with preemption enabled.
> 
> Suggested-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Thanks for cleaning that up!

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>