On 01/10/2018 10:54, Jan Beulich wrote:

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On 01.10.18 at 09:16, jgross@suse.com 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 ...

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frees the lock -> xen_qlock_kick(cpu2)

... need to be below here?

You are right, of course!

Thanks for noticing.

Juergen