22.06.2021 13:20, Paolo Bonzini wrote:
On 22/06/21 11:36, Vladimir Sementsov-Ogievskiy wrote:
It does. If it returns true, you still want the load of finished to happen
before the reads that follow.
Hmm.. The worst case if we use just qatomic_read is that assertion will not
crash when it actually should. That doesn't break the logic. But that's not
good anyway.
OK, I agree, let's keep it.
You can also have a finished job, but get a stale value for error_is_read or
ret. The issue is not in getting the stale value per se, but in
block_copy_call_status's caller not expecting it.
(I understand you agree, but I guess it can be interesting to learn about this
too).
Hmm. So, do you mean that we can read ret and error_is_read ONLY after
explicitly doing load_acquire(finished) and checking that it's true?
That means that we must do it not in assertion (to not be compiled out):
bool finished = load_acquire()
assert(finished);
... read reat and error_is_read ...
--
Best regards,
Vladimir
