On 11/02/2026 16:52, Tom Lane wrote:
> Ashutosh Bapat <ashutosh.bapat.oss@gmail.com> writes:
>> On Wed, Feb 11, 2026 at 8:46 AM Chao Li <li.evan.chao@gmail.com> wrote:
>>> But I don’t see a replacement like SpinLockInit(&ProcGlobal->freeProcsLock);
>
>> Good catch.
>
> Undoubtedly, this escaped Heikki's notice because on all supported
> platforms SpinLockInit() initializes the spinlock value to zero,
> but shared memory starts out zeroes anyway.
Right.
> We used to have better odds of catching such mistakes. My old HPPA
> dinosaur would have caught it by dint of needing a nonzero initial
> value, but that hardware is long gone. The test infrastructure
> we used to have for emulating spinlocks with SysV semaphores would
> have caught it too, I think, but that's also gone.
>
> This is not a great situation. I wonder if we can put back some
> mode that could be used by a few BF members to catch such oversights.
Do we still support any architectures where initializing the spinlock to
all-zeros doesn't do the right thing? Could we accept that all-zeros is
a valid initialization of a spinlock? This reminds me that Thomas was
working on re-implementing spinlocks with atomics [1]. With that least,
I presume we could.
[1]
https://www.postgresql.org/message-id/CA%2BhUKGKFvu3zyvv3aaj5hHs9VtWcjFAmisOwOc7aOZNc5AF3NA%40mail.gmail.com
- Heikki
