Re: cpu stopper threads and setaffinity leads to deadlock

[Sodagudi Prasad]

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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