Re: PATCH: Rimmerworld pipeline race

[Peter Stephenson <p.stephenson@xxxxxxxxxxx>]

On Tue, 11 Sep 2018 16:03:26 +0100
Peter Stephenson <p.stephenson@xxxxxxxxxxx> wrote:

> On Tue, 11 Sep 2018 16:40:46 +0200
> Vincent Lefevre <vincent@xxxxxxxxxx> wrote:
> > Apparently, it is not entirely fixed, or perhaps this is another
> > problem:
> > 
> > cventin% for i in 1 2 3; do : | { : | tput init } done
> > zsh: suspended (tty output)  for i in 1 2 3; do; : | { : | tput init; }; done  
> 
> You can get it with any outer current-shell construct.
> 
> { : | { : | more } }
> 
> Looks a bit different to me.  Not happening in the instrumented build
> on the job_control_debug branch, either, so even harder to debug.

OK, suppose we also pass back information about list_pipe_job itself,
not just the group leader?  This seems to work for me.

I'm in two minds whether to pass the whole structure into addproc(): it
seems to be abusing the interface.

pws

diff --git a/Src/exec.c b/Src/exec.c
index 074265f..b9af9ea 100644
--- a/Src/exec.c
+++ b/Src/exec.c
@@ -1002,7 +1002,7 @@ enum {
 
 /**/
 static void
-entersubsh(int flags, int *gleaderp)
+entersubsh(int flags, struct entersubsh_ret *retp)
 {
     int i, sig, monitor, job_control_ok;
 
@@ -1036,8 +1036,10 @@ entersubsh(int flags, int *gleaderp)
 		if (!(flags & ESUB_ASYNC))
 		    attachtty(jobtab[thisjob].gleader);
 	    }
-	    if (gleaderp)
-		*gleaderp = jobtab[list_pipe_job].gleader;
+	    if (retp) {
+		retp->gleader = jobtab[list_pipe_job].gleader;
+		retp->list_pipe_job = list_pipe_job;
+	    }
 	}
 	else if (!jobtab[thisjob].gleader ||
 		 setpgrp(0L, jobtab[thisjob].gleader) == -1) {
@@ -1058,8 +1060,11 @@ entersubsh(int flags, int *gleaderp)
 	    setpgrp(0L, jobtab[thisjob].gleader);
 	    if (!(flags & ESUB_ASYNC))
 		attachtty(jobtab[thisjob].gleader);
-	    if (gleaderp)
-		*gleaderp = jobtab[thisjob].gleader;
+	    if (retp) {
+		retp->gleader = jobtab[thisjob].gleader;
+		if (list_pipe_job != thisjob)
+		    retp->list_pipe_job = list_pipe_job;
+	    }
 	}
     }
     if (!(flags & ESUB_FAKE))
@@ -1692,7 +1697,7 @@ execpline(Estate state, wordcode slcode, int how, int last1)
 		    curjob = newjob;
 		    DPUTS(!list_pipe_pid, "invalid list_pipe_pid");
 		    addproc(list_pipe_pid, list_pipe_text, 0,
-			    &list_pipe_start, -1);
+			    &list_pipe_start, -1, -1);
 
 		    /* If the super-job contains only the sub-shell, the
 		       sub-shell is the group leader. */
@@ -2185,7 +2190,7 @@ closemn(struct multio **mfds, int fd, int type)
 	    }
 	    mn->ct = 1;
 	    mn->fds[0] = fd;
-	    addproc(pid, NULL, 1, &bgtime, -1);
+	    addproc(pid, NULL, 1, &bgtime, -1, -1);
 	    child_unblock();
 	    return;
 	}
@@ -2686,10 +2691,12 @@ execcmd_fork(Estate state, int how, int type, Wordcode varspc,
 {
     pid_t pid;
     int synch[2], flags;
-    int gleader = -1;
+    struct entersubsh_ret esret;
     struct timeval bgtime;
 
     child_block();
+    esret.gleader = -1;
+    esret.list_pipe_job = -1;
 
     if (pipe(synch) < 0) {
 	zerr("pipe failed: %e", errno);
@@ -2703,7 +2710,7 @@ execcmd_fork(Estate state, int how, int type, Wordcode varspc,
     }
     if (pid) {
 	close(synch[1]);
-	read_loop(synch[0], (char *)&gleader, sizeof(gleader));
+	read_loop(synch[0], (char *)&esret, sizeof(esret));
 	close(synch[0]);
 	if (how & Z_ASYNC) {
 	    lastpid = (zlong) pid;
@@ -2721,7 +2728,7 @@ execcmd_fork(Estate state, int how, int type, Wordcode varspc,
 		      3 : WC_ASSIGN_NUM(ac) + 2);
 	    }
 	}
-	addproc(pid, text, 0, &bgtime, gleader);
+	addproc(pid, text, 0, &bgtime, esret.gleader, esret.list_pipe_job);
 	if (oautocont >= 0)
 	    opts[AUTOCONTINUE] = oautocont;
 	pipecleanfilelist(jobtab[thisjob].filelist, 1);
@@ -2736,8 +2743,8 @@ execcmd_fork(Estate state, int how, int type, Wordcode varspc,
     if (type == WC_SUBSH && !(how & Z_ASYNC))
 	flags |= ESUB_JOB_CONTROL;
     *filelistp = jobtab[thisjob].filelist;
-    entersubsh(flags, &gleader);
-    write(synch[1], &gleader, sizeof(gleader));
+    entersubsh(flags, &esret);
+    write(synch[1], &esret, sizeof(esret));
     close(synch[1]);
     zclose(close_if_forked);
 
@@ -4876,7 +4883,7 @@ getproc(char *cmd, char **eptr)
 	if (pid == -1)
 	    return NULL;
 	if (!out)
-	    addproc(pid, NULL, 1, &bgtime, -1);
+	    addproc(pid, NULL, 1, &bgtime, -1, -1);
 	procsubstpid = pid;
 	return pnam;
     }
@@ -4913,7 +4920,7 @@ getproc(char *cmd, char **eptr)
 	addfilelist(NULL, fd);
 	if (!out)
 	{
-	    addproc(pid, NULL, 1, &bgtime, -1);
+	    addproc(pid, NULL, 1, &bgtime, -1, -1);
 	}
 	procsubstpid = pid;
 	return pnam;
@@ -4965,7 +4972,7 @@ getpipe(char *cmd, int nullexec)
 	    return -1;
 	}
 	if (!nullexec)
-	    addproc(pid, NULL, 1, &bgtime, -1);
+	    addproc(pid, NULL, 1, &bgtime, -1, -1);
 	procsubstpid = pid;
 	return pipes[!out];
     }
diff --git a/Src/jobs.c b/Src/jobs.c
index ba87a17..db2e87e 100644
--- a/Src/jobs.c
+++ b/Src/jobs.c
@@ -1375,7 +1375,8 @@ deletejob(Job jn, int disowning)
 
 /**/
 void
-addproc(pid_t pid, char *text, int aux, struct timeval *bgtime, int gleader)
+addproc(pid_t pid, char *text, int aux, struct timeval *bgtime,
+	int gleader, int list_pipe_job_used)
 {
     Process pn, *pnlist;
 
@@ -1397,10 +1398,15 @@ addproc(pid_t pid, char *text, int aux, struct timeval *bgtime, int gleader)
 	 * the job, then it's the group leader.
 	 *
 	 * Exception: if the forked subshell reported its own group
-	 * leader, set that.
+	 * leader, set that.  If it reported the use of list_pipe_job,
+	 * set it for that, too.
 	 */
-	if (!jobtab[thisjob].gleader)
-	    jobtab[thisjob].gleader = (gleader != -1) ? gleader : pid;
+	if (gleader != -1) {
+	    jobtab[thisjob].gleader = gleader;
+	    if (list_pipe_job_used != -1)
+		jobtab[list_pipe_job_used].gleader = gleader;
+	} else if (!jobtab[thisjob].gleader)
+		jobtab[thisjob].gleader = pid;
 	/* attach this process to end of process list of current job */
 	pnlist = &jobtab[thisjob].procs;
     }
diff --git a/Src/zsh.h b/Src/zsh.h
index 8e7f20b..b81db15 100644
--- a/Src/zsh.h
+++ b/Src/zsh.h
@@ -505,6 +505,14 @@ enum {
     ZCONTEXT_PARSE      = (1<<2)
 };
 
+/* Report from entersubsh() to pass subshell info to addproc */
+struct entersubsh_ret {
+    /* Process group leader chosen by subshell, else -1 */
+    int gleader;
+    /* list_pipe_job setting used by subshell, else -1 */
+    int list_pipe_job;
+};
+
 /**************************/
 /* Abstract types for zsh */
 /**************************/