Re: bin/47524: make(1) loops in Job_CatchOutput()

[David Laight <david%l8s.co.uk@localhost>]

On Sat, Feb 02, 2013 at 02:15:01PM +0000, Andreas Gustafsson wrote:
> >Number:         47524
> >Category:       bin
> >Synopsis:       make(1) loops in Job_CatchOutput()
...
> @@ -2046,7 +2050,8 @@
>      if (nready < 0 || readyfd(&childExitJob)) {
>       char token = 0;
>       nready -= 1;
> -     (void)read(childExitJob.inPipe, &token, 1);
> +     while (read(childExitJob.inPipe, &token, 1) == -1 && errno == EAGAIN)
> +             continue;
>       if (token == DO_JOB_RESUME[0])
>           /* Complete relay requested from our SIGCONT handler */
>           JobRestartJobs();
> 
> I believe the "while" loop added by this change is where make is now
> looping.

I'd guess that fd in non-blocking so EAGAIN would just mean that the
pipe is empty.
The purpose of the read() is to empty the pipe, If it is already empty
it won't matter.
I think you'll find the sigchild handler writes into it, possibly
with some check of nready (not looked) to wake things up.

Most likely two children finishing at once only write 1 character,
or some path comes in with nready < 0 ...

        David

-- 
David Laight: david%l8s.co.uk@localhost