Re: Parallel worker hangs while handling errors.

On Sat, Jul 25, 2020 at 7:02 AM vignesh C <vignesh21@gmail.com> wrote:
>
> I have made slight changes on top of the patch to remove duplicate
> code, attached v3 patch for the same.
> The parallel worker hang issue gets resolved, make check & make
> check-world passes.
>

Having a function to unblock selective signals for a bg worker looks good to me.

Few comments:
1. Do we need "worker" as a function argument in
update_parallel_worker_sigmask(BackgroundWorker *worker,.... ? Since
MyBgworkerEntry is a global variable, can't we have a local variable
instead?
2. Instead of update_parallel_worker_sigmask() serving only for
parallel workers, can we make it generic, so that for any bgworker,
given a signal it unblocks it, although there's no current use case
for a bg worker unblocking a single signal other than a parallel
worker doing it for SIGUSR1 for this hang issue. Please note that we
have BackgroundWorkerBlockSignals() and
BackgroundWorkerUnblockSignals().
I slightly modified your function, something like below?

void
BackgroundWorkerUpdateSignalMask(int signum, bool toblock)
{
    if (toblock)
        sigaddset(&BlockSig, signum);
    else
        sigdelset(&BlockSig, signum);

    PG_SETMASK(&BlockSig);
}

/*to unblock SIGUSR1*/
if ((worker->bgw_flags & BGWORKER_CLASS_PARALLEL) != 0)
    BackgroundWorkerUpdateSignalMask(SIGUSR1, false);

/*to block SIGUSR1*/
if ((worker->bgw_flags & BGWORKER_CLASS_PARALLEL) != 0)
    BackgroundWorkerUpdateSignalMask(SIGUSR1, true);

If okay, with the BackgroundWorkerUpdateSignalMask() function, please
note that we might have to add it in bgworker.sgml as well.

With Regards,
Bharath Rupireddy.
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