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SubjectRe: 5.13-rt1 + KVM = WARNING: at fs/eventfd.c:74 eventfd_signal()
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On 24/07/21 06:33, Hillf Danton wrote:
> lock WQ
> count += n
> no waiter
> unlock WQ

Ok, this is a write.

>
> lock WQ
> add waiter for EPOLLIN
> unlock WQ

This is eventfd_poll(). It hasn't yet returned EPOLLIN.

> lock WQ
> count = 0
> wakeup EPOLLOUT
> unlock WQ

This is a read().

> lock WQ
> count += n
> no waiter
> unlock WQ

This is wrong; after "unlock WQ" in CPU3 there *is* a waiter, no one has
waked it up yet.

Paolo

> ------------------------------- c1 = count

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