On 29/07/2024 20:48, Andres Freund wrote:
On 2024-07-29 13:25:22 -0400, Tom Lane wrote:
Heikki Linnakangas <hlinn...@iki.fi> writes:
Yeah I'm not worried about that at all. Also, the assert is made when
you have already released the spinlock; you are already out of the
critical section.
Not in the patch Andres posted.
Which seems fairly fundamental - once outside of the critical section, we
can't actually assert that the lock isn't acquired, somebody else *validly*
might have acquired it by then.
You could do:
bool was_free = S_LOCK_FREE(lock);
S_UNLOCK(lock);
Assert(!was_free);
Depending on the underlying implementation, you could also use
compare-and-exchange. That makes the assertion-enabled instructions a
little different than without assertions though.
However, I still don't think it's a problem to assert that the lock is held in
in the unlock "routine". As mentioned before, the spinlock implementation
itself has never followed the "just straight line code" rule that users of
spinlocks are supposed to follow.
Agreed.
--
Heikki Linnakangas
Neon (https://neon.tech)
