Re: stopgap fix for signal handling during restore_command

Hi,

On 2023-02-23 20:33:23 -0800, Nathan Bossart wrote:>  
>      if (in_restore_command)
> -        proc_exit(1);
> +    {
> +        /*
> +         * If we are in a child process (e.g., forked by system() in
> +         * RestoreArchivedFile()), we don't want to call any exit callbacks.
> +         * The parent will take care of that.
> +         */
> +        if (MyProcPid == (int) getpid())
> +            proc_exit(1);
> +        else
> +        {
> +            const char    msg[] = "StartupProcShutdownHandler() called in child process\n";
> +            int            rc pg_attribute_unused();
> +
> +            rc = write(STDERR_FILENO, msg, sizeof(msg));
> +            _exit(1);
> +        }
> +    }

Why do we need that rc variable? Don't we normally get away with (void)
write(...)?


> diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c
> index 22b4278610..e3da0622d7 100644
> --- a/src/backend/storage/lmgr/proc.c
> +++ b/src/backend/storage/lmgr/proc.c
> @@ -805,6 +805,7 @@ ProcKill(int code, Datum arg)
>      dlist_head *procgloballist;
>  
>      Assert(MyProc != NULL);
> +    Assert(MyProcPid == (int) getpid());  /* not safe if forked by system(), etc. */
>  
>      /* Make sure we're out of the sync rep lists */
>      SyncRepCleanupAtProcExit();
> @@ -925,6 +926,7 @@ AuxiliaryProcKill(int code, Datum arg)
>      PGPROC       *proc;
>  
>      Assert(proctype >= 0 && proctype < NUM_AUXILIARY_PROCS);
> +    Assert(MyProcPid == (int) getpid());  /* not safe if forked by system(), etc. */
>  
>      auxproc = &AuxiliaryProcs[proctype];
>  
> -- 
> 2.25.1

I think the much more interesting assertion here would be to check that
MyProc->pid equals the current pid.

Greetings,

Andres Freund