Re: [PATCH 1/2] run-command: Remove set_nonblocking

From: Stefan Beller <sbeller@google.com>
Date: Nov 5, 2015, 22:20 UTC
Message-ID: <CAGZ79kZs8HQegNy=L5nGMUGJ98s-xgce1Ncrxpxe_ReaJXMjKw@mail.gmail.com>
In-Reply-To: <563BBBBC.7070807@kdbg.org>

On Thu, Nov 5, 2015 at 12:27 PM, Johannes Sixt <j6t@kdbg.org> wrote:

Show 26 quoted lines

> diff --git a/run-command.c b/run-command.c
> index 51d078c..3e42299 100644
> --- a/run-command.c
> +++ b/run-command.c
> @@ -977,7 +977,7 @@ static struct parallel_processes *pp_init(int n,
>         for (i = 0; i < n; i++) {
>                 strbuf_init(&pp->children[i].err, 0);
>                 child_process_init(&pp->children[i].process);
> -               pp->pfd[i].events = POLLIN;
> +               pp->pfd[i].events = POLLIN|POLLHUP;
>                 pp->pfd[i].fd = -1;
>         }
>         sigchain_push_common(handle_children_on_signal);
> @@ -1061,11 +1061,17 @@ static void pp_buffer_stderr(struct parallel_processes *pp, int output_timeout)
>         /* Buffer output from all pipes. */
>         for (i = 0; i < pp->max_processes; i++) {
>                 if (pp->children[i].in_use &&
> -                   pp->pfd[i].revents & POLLIN)
> -                       if (strbuf_read_once(&pp->children[i].err,
> -                                            pp->children[i].process.err, 0) < 0)
> +                   pp->pfd[i].revents & (POLLIN|POLLHUP)) {
> +                       int n = strbuf_read_once(&pp->children[i].err,
> +                                            pp->children[i].process.err, 0);
> +                       if (n == 0) {
> +                               close(pp->children[i].process.err);
> +                               pp->children[i].process.err = -1;

So you set .err to -1 to signal the process has ended here...

Show 6 quoted lines

> -
>                 for (i = 0; i < pp->max_processes; i++)
>                         if (pp->children[i].in_use &&
> -                           pid == pp->children[i].process.pid)
> +                           pp->children[i].process.err == -1)
>                                 break;

to make a decision here if we want to finish_command on it.

> +               code = finish_command(&pp->children[i].process);

> -               child_process_clear(&pp->children[i].process);

but .err stays stays -1 here for the next iteration? We would need to reset it to 0 again.

So .err is
  0 when the slot is not in use
 -1 when the child has finished awaiting termination
 >0 when the child is living a happy life.