Re: Interruptible sleeps (was Re: CommitFest 2009-07: Yay, Kevin! Thanks, reviewers!)

Fujii Masao <masao.fujii@gmail.com> writes:
>> +               * XXX: Is it safe to elog(ERROR) in a signal handler?
>> 
>> No, it isn't.

> We should use elog(FATAL) or check proc_exit_inprogress, instead?

elog(FATAL) is *certainly* not a better idea.  I think there's really
nothing that can be done, you just have to silently ignore the error.
BTW, if we retry, there had probably better be a limit on how many times
to retry ...

> +        if (errno != EAGAIN && errno != EWOULDBLOCK)
> +        {
> +            /*
> +             * XXX: Is it safe to elog(ERROR) in a signal handler?
> +             */
> +            elog(ERROR, "write() on self-pipe failed: %m");
> +        }
> +        if (errno == EINTR)
> +            goto retry;

> "errno == EINTR)" seems to be never checked.

Another issue with coding like that is that it supposes elog() won't
change errno.
        regards, tom lane