Re: How to handle waitingForLock in LockWaitCancel()

Tom Lane wrote:
> 
> Hiroshi Inoue <Inoue@tpf.co.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