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Date:   Fri, 03 Aug 2018 11:57:23 -0700
From:   Sodagudi Prasad <psodagud@codeaurora.org>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Peter Zijlstra <peterz@infradead.org>, mingo@kernel.org,
        gregkh@linuxfoundation.org, bigeasy@linutronix.de,
        isaacm@codeaurora.org, linux-kernel@vger.kernel.org
Subject: Re: cpu stopper threads and setaffinity leads to deadlock
In-Reply-To: <alpine.DEB.2.21.1808031340500.1745@nanos.tec.linutronix.de>
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 <alpine.DEB.2.21.1808031340500.1745@nanos.tec.linutronix.de>
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On 2018-08-03 04:41, Thomas Gleixner wrote:
> 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?
<Prasad> Hi Thomas and Peter,

Yes. Tested both versions of patches and both variants are working on 
Qualcomm devices
with stress testing of set affinity and tasks cross-migration, which 
were previously leading to the deadlock.

-Thanks, Prasad
> 
>> --- 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;
>>  }
>> 

-- 
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