Re: zsh hangs sometimes continued.

[Peter Stephenson <Peter.Stephenson@xxxxxxx>]

On Thu, 31 Mar 2011 20:32:58 +0200
VAN VLIERBERGHE Stef <stef.van-vlierberghe@xxxxxxxxxxxxxxx> wrote:
> After adding more and more debug info to the zsh-4.3.10 sources I
> figured out that the problem is in the findjob returning the pid of
> a terminated process.

Thanks for the investigation and the explanation.  I agree the uses of
findproc() all appear to assume the process is still marked as running,
since they are all about to update it.  Here's the patch I'll apply.

Index: Src/jobs.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/jobs.c,v
retrieving revision 1.79
diff -p -u -r1.79 jobs.c
--- Src/jobs.c	22 Aug 2010 20:08:57 -0000	1.79
+++ Src/jobs.c	1 Apr 2011 09:09:54 -0000
@@ -173,11 +173,28 @@ findproc(pid_t pid, Job *jptr, Process *
 
 	for (pn = aux ? jobtab[i].auxprocs : jobtab[i].procs;
 	     pn; pn = pn->next)
-	    if (pn->pid == pid) {
+	{
+	    /*
+	     * Make sure we match a process that's still running.
+	     *
+	     * When a job contains two pids, one terminated pid and one
+	     * running pid, then the condition (jobtab[i].stat &
+	     * STAT_DONE) will not stop these pids from being candidates
+	     * for the findproc result (which is supposed to be a
+	     * RUNNING pid), and if the terminated pid is an identical
+	     * process number for the pid identifying the running
+	     * process we are trying to find (after pid number
+	     * wrapping), then we need to avoid returning the terminated
+	     * pid, otherwise the shell would block and wait forever for
+	     * the termination of the process which pid we were supposed
+	     * to return in a different job.
+	     */
+	    if (pn->pid == pid && pn->status == SP_RUNNING) {
 		*pptr = pn;
 		*jptr = jobtab + i;
 		return 1;
 	    }
+	}
     }
 
     return 0;

-- 
Peter Stephenson <pws@xxxxxxx>            Software Engineer
Tel: +44 (0)1223 692070                   Cambridge Silicon Radio Limited
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