Date: Fri, 4 Oct 2024 11:57:48 -0700
From: Noah Misch <noah@leadboat.com>
To: Alexander Lakhin <exclusion@gmail.com>
Cc: pgsql-hackers@postgresql.org, Robert Haas <robertmhaas@gmail.com>
Subject: Re: IPC::Run accepts bug reports
Message-ID: <20241004185748.22.nmisch@google.com>
References: <20240615234824.a9@rfd.leadboat.com>
 <fb666566-32bb-9c36-9c2e-3949b7a061bc@gmail.com>
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On Fri, Oct 04, 2024 at 02:00:00PM +0300, Alexander Lakhin wrote:
> sub _read {
> ...
>     my $r = POSIX::read( $_[0], $s, 10_000 );
>     croak "$!: read( $_[0] )" if not($r) and !$!{EINTR};
> 
> That is, EINTR kind of recognized as an expected error, but there is no
> retry in this case. Thus, with the following modification, which simulates
> read() failed with EINTR:
>  sub _read {
>      confess 'undef' unless defined $_[0];
>      my $s = '';
> -    my $r = POSIX::read( $_[0], $s, 10_000 );
> +    my $r;
> +if (int(rand(100)) == 0)
> +{
> +   $r = 0;  $! = Errno::EINTR;
> +}
> +else
> +{
> +    $r = POSIX::read( $_[0], $s, 10_000 );
> +}
>      croak "$!: read( $_[0] )" if not($r) and !$!{EINTR};
> 
> I can see failures like the one in question when running that test.

That makes sense.  Would you file this at
https://github.com/cpan-authors/IPC-Run/issues?  I suppose that code should
become roughly:

  do { $r = POSIX::read(...) } while (!defined($r) && $!{EINTR});
  croak ... unless defined($r);

> Perhaps, I could reproduce the issue with a program, that sends signals
> to running (pgbench) processes (and thus interrupts read()), if it makes
> sense.

That should work.  Best would be an IPC::Run test case, like the existing
t/eintr.t that makes select() report EINTR.  That said, IPC::Run could adopt
the retry without a test.

> [1] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=indri&dt=2024-10-02%2002%3A34%3A16