Date: Fri, 28 Apr 2000 11:04:05 -0400 (EDT) From: Vivek Khera <khera@kciLink.com> To: stable@freebsd.org Subject: Cron setting SIGCHLD to SIG_IGN Message-ID: <14601.43109.419114.997113@onceler.kcilink.com>
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There was a nice little bug found in Cron over on the BSDI users
mailing list. Apparently SIGCHLD is ignored when the child command is
run, and perl 5.6.0 complains about it. The fix is to cron.
This seems to be applicable for FreeBSD 3.4-STABLE and 4.0-STABLE
according to the sources as of today, as well.
Attached is the patch from Paul Vixie.
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References: <200004271826.OAA23896@iridium.mv.net>
In-Reply-To: mem@mv.mv.com's message of "27 Apr 2000 11:22:33 -0700"
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From: Paul A Vixie <vixie@mibh.net>
Sender: bsdi-users-return-2689-khera=kci.kcilink.com@mailinglists.org
To: bsdi-users@bsdi.com
Subject: Re: Cron setting SIGCHLD to SIG_IGN
Date: Thu, 27 Apr 2000 14:47:02 -0700
mem@mv.mv.com ("Mark E. Mallett") writes:
> Looking at the cron source code, I do see that cron is forcing
> SIGCHLD to SIG_IGN for the children that it spawns. I'm afraid that
> the reasoning behind this move escapes me.
It's because cron (then called crond) was the first program I ever wrote
that used signals or called fork or exec. This was in 1986, just after
4.3BSD came out, and well before signals had been posixified. signal(2)
says, quite clearly:
When a process which has installed signal handlers forks, the child pro-
cess inherits the signals. All caught signals may be reset to their de-
fault action by a call to the execve(2) function; ignored signals remain
ignored.
This means that having set SIGCHLD to SIG_IGN for my own purposes, I really
needed (and apparently still need) to set it back to SIG_DFL before fork()'ing
to run each command found in a crontab. Ouch! Sorry, all. Here's a patch
against cron 4.0 (see ftp://ftp.isc.org/isc/cron/, since this is more recent
than what ships with BSD/OS). The patch ought to apply, with some fuzz, to
the shipping version.
Index: do_command.c
===================================================================
RCS file: /proj/src/isc/cvs-1/cron/do_command.c,v
retrieving revision 1.4
diff -u -r1.4 do_command.c
--- do_command.c 2000/01/02 20:53:41 1.4
+++ do_command.c 2000/04/27 18:45:37
@@ -222,6 +222,13 @@
chdir(env_get("HOME", e->envp));
/*
+ * Since ignored signals remain ignored after fork()/exec(),
+ * we need to unignore our ignored signals before letting
+ * some unsuspecting user level command inherit them.
+ */
+ (void) signal(SIGCHLD, SIG_DFL);
+
+ /*
* Exec the command.
*/
{
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