Re: [PATCH 1/4] run-command: add new check_command helper

On Mon, Apr 1, 2013 at 11:14 PM, Jeff King [off-list ref] wrote:

On Mon, Apr 01, 2013 at 11:11:20PM -0600, Felipe Contreras wrote:

quoted

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But if we know from reading waitpid(3) that waitpid should only fail due
to EINTR, or due to bogus arguments (e.g., a pid that does not exist or
has already been reaped), then maybe something like this makes sense:

  while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
          ; /* nothing */

But we don't want to wait synchronously here, we just want to ping.

Yeah, sorry, I forgot the WNOHANG there.

It still can potentially stay in a loop for some cycles.

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After the fix above, yes; in the original we would always have exited
already.

No:

+       if (waiting != cmd->pid)
+               return 1;

If waiting < 0, waiting != cmd->pid, and therefore this return is not
triggered, and there's only one more return at the end of the
function.

Are my eyes not working? If waiting < 0, then waiting != cmd->pid, and
therefore this return _is_ triggered.

Oh, right, it's only after the modification that the code works.

-- 
Felipe Contreras