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

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Message-ID: <712493a7926b0f58543be052ced95db9@codeaurora.org>
Date:   Fri, 03 Aug 2018 11:57:23 -0700
From:   Sodagudi Prasad <psodagud@...eaurora.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Peter Zijlstra <peterz@...radead.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

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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