Il ven 16 mag 2025, 08:58 Akihiko Odaki <[email protected]> ha
scritto:
> I also found smp_mb__after_rmw() before qemu_futex_wake_all() is no
> longer necessary. Summing up, I think the code should look like as follows:
>
> #ifdef HAVE_FUTEX
>
You would still need smp_mb__before_rmw() here.
if (qatomic_xchg(&ev->value, EV_SET) == EV_BUSY) {
>
Removing the qatomic_read() works, but it's more expensive in the case that
the event is already set.
The barrier before qemu_futex_wake_all(ev) could be unnecessary because
there is probably one in FUTEX_WAKE. But not being able to audit Windows
makes me a bit uneasy about it.
Paolo
/* There were waiters, wake them up. */
> qemu_futex_wake_all(ev);
> }
#else
> pthread_mutex_lock(&ev->lock);
> qatomic_store_release(&ev->value, EV_SET);
> pthread_cond_broadcast(&ev->cond);
> pthread_mutex_unlock(&ev->lock);
> #endif
>
> Regards,
> Akihiko Odaki
>
>
