linux-kernel - Re: cpu stopper threads and setaffinity leads to deadlock

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Message-ID: <alpine.DEB.2.21.1808031340500.1745@nanos.tec.linutronix.de>
Date:   Fri, 3 Aug 2018 13:41:13 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     Sodagudi Prasad <psodagud@...eaurora.org>, mingo@...nel.org,
        gregkh@...uxfoundation.org, bigeasy@...utronix.de,
        isaacm@...eaurora.org, linux-kernel@...r.kernel.org
Subject: Re: cpu stopper threads and setaffinity leads to deadlock

Prasad.

On Thu, 2 Aug 2018, Peter Zijlstra wrote:
> 
> So why didn't you do the 'obvious' parallel to what you did for
> cpu_stop_queue_two_works(), namely:

Is that patch fixing the issue for you?

> --- a/kernel/stop_machine.c
> +++ b/kernel/stop_machine.c
> @@ -81,6 +81,7 @@ static bool cpu_stop_queue_work(unsigned
>  	unsigned long flags;
>  	bool enabled;
>  
> +	preempt_disable();
>  	raw_spin_lock_irqsave(&stopper->lock, flags);
>  	enabled = stopper->enabled;
>  	if (enabled)
> @@ -90,6 +91,7 @@ static bool cpu_stop_queue_work(unsigned
>  	raw_spin_unlock_irqrestore(&stopper->lock, flags);
>  
>  	wake_up_q(&wakeq);
> +	preempt_enable();
>  
>  	return enabled;
>  }
>