On 3/6/23 14:31, David Hildenbrand wrote:
- smp_mb_acquire();
- if (value == EV_SET) {
- /* If there was a concurrent reset (or even reset+wait),
- * do nothing. Otherwise change EV_SET->EV_FREE.
- */
- qatomic_or(&ev->value, EV_FREE);
- }
+
[had the same thought on patch #2]
IIUC, the "read first" is an optimization to not unconditionally dirty
the cache-line. But I assume we don't particularly care about that
optimization on the reset path.
Thinking more about it, the intended usage of QemuEvent is either
qemu_event_reset();
if (!check()) {
qemu_event_wait());
}
or
if (!check()) {
qemu_event_reset();
if (!check()) {
qemu_event_wait());
}
}
If we don't care on the reset path we care much less on the wait path.
Should I remove it and go straight to the cmpxchg, just for peace of mind?
Paolo
