Re: How to handle waitingForLock in LockWaitCancel()

Tom Lane wrote:
>
> Hiroshi Inoue <Inoue(at)tpf(dot)co(dot)jp> writes:
> > [ backtrace snipped ]
>
> Hmm, this is definitely not operating as intended: LockWaitCancel is
> getting interrupted, because ProcessInterrupts may be called when it's
> trying to acquire the lockmanager spinlock, and ProcessInterrupts will
> see the ProcDiePending flag already set. I think the correct fix (or
> at least part of it) is in postgres.c's die():
>
> /*
> * If it's safe to interrupt, and we're waiting for input or a lock,
> * service the interrupt immediately
> */
> if (ImmediateInterruptOK && InterruptHoldoffCount == 0 &&
> CritSectionCount == 0)
> {
> + /* bump holdoff count to make ProcessInterrupts() a no-op */
> + /* until we are done getting ready for it */
> + InterruptHoldoffCount++;
> DisableNotifyInterrupt();
> /* Make sure HandleDeadLock won't run while shutting down... */
> LockWaitCancel();
> + InterruptHoldoffCount--;
> ProcessInterrupts();
> }
>
> QueryCancelHandler probably needs similar additions.
>

Agreed. Adding similar code to QueryCancelHandler seems
sufficient.

> I suspect you will find that these crashes occur during the window just
> after

Sorry what does 'just after' mean ?
Isn't it during the semop() ?

> the semop() call in IpcSemaphoreLock() --- see the comment

Regards,
Hiroshi Inoue