From: Peter Stephenson <p.stephenson@samsung.com>
To: zsh-workers@zsh.org
Subject: Re: Signal handling bugaboo in command substitution
Date: Tue, 08 Mar 2016 10:00:04 +0000 [thread overview]
Message-ID: <20160308100004.3011d110@pwslap01u.europe.root.pri> (raw)
In-Reply-To: <160307184406.ZM23121@torch.brasslantern.com>
On Mon, 07 Mar 2016 18:44:06 -0800
Bart Schaefer <schaefer@brasslantern.com> wrote:
> At a PS1 prompt:
>
> torch% print $(sleep 3; echo foo)
>
> Press ctrl+z during the sleep. Zsh is now hung, because the command
> substitution is occuring in prefork() so there's nothing to handle the
> stopped children and the parent itself ignores the signal. Zsh is hung;
> it won't return to a prompt, the command substitution will never produce
> the awaited output, and nothing (except "kill -CONT" from another shell)
> will wake it back up.
>
> I'm not sure what to do here. In other circumstances it's OK to stop a
> command substitution with a ctrl+z, and in any kind of non-interactive
> shell or even in a subshell the parent would handle the signal.
>
> Bash appears to leave TSTP blocked here when interactive. I don't think
> testing for interactivity is sufficient in zsh context, though.
How about something like this?
pws
diff --git a/Src/exec.c b/Src/exec.c
index b60fc90..caeb461 100644
--- a/Src/exec.c
+++ b/Src/exec.c
@@ -1001,9 +1001,21 @@ entersubsh(int flags)
* signals. If it is, we need to keep the special behaviour:
* see note about attachtty() above.
*/
- signal_default(SIGTTOU);
- signal_default(SIGTTIN);
- signal_default(SIGTSTP);
+ if (flags & ESUB_NOMONITOR)
+ {
+ /*
+ * Allowing any form of interactive signalling here is
+ * actively harmful as we are in a context where there is no
+ * control over the process.
+ */
+ signal_ignore(SIGTTOU);
+ signal_ignore(SIGTTIN);
+ signal_ignore(SIGTSTP);
+ } else {
+ signal_default(SIGTTOU);
+ signal_default(SIGTTIN);
+ signal_default(SIGTSTP);
+ }
}
if (interact) {
signal_default(SIGTERM);
next prev parent reply other threads:[~2016-03-08 10:10 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-08 2:44 Bart Schaefer
2016-03-08 10:00 ` Peter Stephenson [this message]
2016-03-08 10:12 ` Peter Stephenson
2016-03-08 17:30 ` Bart Schaefer
2016-03-09 9:55 ` Peter Stephenson
2016-03-09 15:37 ` Bart Schaefer
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