Re: [Xen-devel] [PATCH 1/2] xen: fix race in xen_qlock_wait()

[Juergen Gross]

On 01/10/2018 10:54, Jan Beulich wrote:
>>>> On 01.10.18 at 09:16, <jgross@xxxxxxxx> wrote:
>> In the following situation a vcpu waiting for a lock might not be
>> woken up from xen_poll_irq():
>>
>> CPU 1:                CPU 2:                      CPU 3:
>> takes a spinlock
>>                       tries to get lock
>>                       -> xen_qlock_wait()
>>                         -> xen_clear_irq_pending()
> 
> Doesn't the last line above ...
> 
>> frees the lock
>> -> xen_qlock_kick(cpu2)
> 
> ... need to be below here?

You are right, of course!

Thanks for noticing.


Juergen