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[src/trunk]: src/bin/sh Add lots of comments explaining what is happening in ...
details: https://anonhg.NetBSD.org/src/rev/5c303fbb1d6d
branches: trunk
changeset: 1013102:5c303fbb1d6d
user: kre <kre%NetBSD.org@localhost>
date: Thu Aug 20 23:03:17 2020 +0000
description:
Add lots of comments explaining what is happening in here.
Also enhance some of the DEBUG mode trace output (nothing visible
in a normal shell build).
A couple of very minor code changes that no-one should ever notice
(eg: one less wait() call in the case that there is nothing pending).
diffstat:
bin/sh/jobs.c | 160 ++++++++++++++++++++++++++++++++++++++++++++++++++-------
1 files changed, 140 insertions(+), 20 deletions(-)
diffs (284 lines):
diff -r ae43324cfac9 -r 5c303fbb1d6d bin/sh/jobs.c
--- a/bin/sh/jobs.c Thu Aug 20 23:03:08 2020 +0000
+++ b/bin/sh/jobs.c Thu Aug 20 23:03:17 2020 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: jobs.c,v 1.107 2020/02/07 02:06:12 kre Exp $ */
+/* $NetBSD: jobs.c,v 1.108 2020/08/20 23:03:17 kre Exp $ */
/*-
* Copyright (c) 1991, 1993
@@ -37,7 +37,7 @@
#if 0
static char sccsid[] = "@(#)jobs.c 8.5 (Berkeley) 5/4/95";
#else
-__RCSID("$NetBSD: jobs.c,v 1.107 2020/02/07 02:06:12 kre Exp $");
+__RCSID("$NetBSD: jobs.c,v 1.108 2020/08/20 23:03:17 kre Exp $");
#endif
#endif /* not lint */
@@ -380,6 +380,18 @@
return;
INTOFF;
for (e = i = 0; i < jp->nprocs; i++) {
+ /*
+ * Don't touch a process we already waited for and collected
+ * exit status, that pid may have been reused for something
+ * else - even another of our jobs
+ */
+ if (jp->ps[i].status != -1 && !WIFSTOPPED(jp->ps[i].status))
+ continue;
+
+ /*
+ * Otherwise tell it to continue, if it worked, we're done
+ * (we signal the whole process group)
+ */
if (killpg(jp->ps[i].pid, SIGCONT) != -1)
break;
if (e == 0 && errno != ESRCH)
@@ -387,6 +399,11 @@
}
if (i >= jp->nprocs)
error("Cannot continue job (%s)", strerror(e ? e : ESRCH));
+
+ /*
+ * Now change state of all stopped processes in the job to running
+ * If there were any, the job is now running as well.
+ */
for (ps = jp->ps, i = jp->nprocs ; --i >= 0 ; ps++) {
if (WIFSTOPPED(ps->status)) {
VTRACE(DBG_JOBS, (
@@ -570,10 +587,10 @@
CTRACE(DBG_JOBS, ("showjobs(%x) called\n", mode));
- /* If not even one one job changed, there is nothing to do */
- gotpid = dowait(WSILENT, NULL, NULL);
- while (dowait(WSILENT, NULL, NULL) > 0)
- continue;
+ /* Collect everything pending in the kernel */
+ if ((gotpid = dowait(WSILENT, NULL, NULL)) > 0)
+ while (dowait(WSILENT, NULL, NULL) > 0)
+ continue;
#ifdef JOBS
/*
* Check if we are not in our foreground group, and if not
@@ -813,19 +830,25 @@
/*
* There is at least 1 job running, so we can
- * safely wait() for something to exit.
+ * safely wait() (blocking) for something to exit.
*/
if (jp->state == JOBRUNNING) {
job = NULL;
if ((i = dowait(WBLOCK|WNOFREE, NULL, &job)) == -1)
return 128 + lastsig();
- if (job == NULL) /* an interloper */
+ /*
+ * This happens if an interloper has died
+ * (eg: a child of the executable that exec'd us)
+ * Simply go back and start all over again
+ * (this is rare).
+ */
+ if (job == NULL)
continue;
/*
- * one of the job's processes exited,
- * but there are more
+ * one of the reported job's processes exited,
+ * but there are more still running, back for more
*/
if (job->state == JOBRUNNING)
continue;
@@ -1314,7 +1337,17 @@
/*
- * Wait for a process to terminate.
+ * Wait for a process (any process) to terminate.
+ *
+ * If "job" is given (not NULL), then its jobcontrol status (and mflag)
+ * are used to determine if we wait for stopping/continuing processes or
+ * only terminating ones, and the decision whether to report to stdout
+ * or not varies depending what happened, and whether the affected job
+ * is the one that was requested or not.
+ *
+ * If "changed" is not NULL, then the job which changed because a
+ * process terminated/stopped will be reported by setting *changed,
+ * if there is any such job, otherwise we set *changed = NULL.
*/
STATIC int
@@ -1327,53 +1360,123 @@
struct job *thisjob;
int done;
int stopped;
+ int err;
- VTRACE(DBG_JOBS|DBG_PROCS, ("dowait(%x) called\n", flags));
+ VTRACE(DBG_JOBS|DBG_PROCS, ("dowait(%x) called for job %d%s\n",
+ flags, (job ? job-jobtab+1 : 0), changed ? " [report change]":""));
if (changed != NULL)
*changed = NULL;
+ /*
+ * First deal with the kernel, collect info on any (one) of our
+ * children that has changed state since we last asked.
+ * (loop if we're interrupted by a signal that we aren't processing)
+ */
do {
+ err = 0;
pid = waitproc(flags & WBLOCK, job, &status);
- VTRACE(DBG_JOBS|DBG_PROCS, ("wait returns pid %d, status %#x\n",
- pid, status));
- } while (pid == -1 && errno == EINTR && pendingsigs == 0);
+ if (pid == -1)
+ err = errno;
+ VTRACE(DBG_JOBS|DBG_PROCS,
+ ("wait returns pid %d (e:%d), status %#x (ps=%d)\n",
+ pid, err, status, pendingsigs));
+ } while (pid == -1 && err == EINTR && pendingsigs == 0);
+
+ /*
+ * if nothing exited/stopped/..., we have nothing else to do
+ */
if (pid <= 0)
return pid;
+
+ /*
+ * Otherwise, try to find the process, somewhere in our job table
+ */
INTOFF;
thisjob = NULL;
for (jp = jobtab ; jp < jobtab + njobs ; jp++) {
if (jp->used) {
- done = 1;
- stopped = 1;
+ /*
+ * For each job that is in use (this is one)
+ */
+ done = 1; /* assume it is finished */
+ stopped = 1; /* and has stopped */
+
+ /*
+ * Now scan all our child processes of the job
+ */
for (sp = jp->ps ; sp < jp->ps + jp->nprocs ; sp++) {
if (sp->pid == -1)
continue;
+ /*
+ * If the process that changed is the one
+ * we're looking at, and it was previously
+ * running (-1) or was stopped (anything else
+ * and it must have already finished earlier,
+ * so cannot be the process that just changed)
+ * then we update its status
+ */
if (sp->pid == pid &&
(sp->status==-1 || WIFSTOPPED(sp->status))) {
VTRACE(DBG_JOBS | DBG_PROCS,
("Job %d: changing status of proc %d from %#x to %#x\n",
jp - jobtab + 1, pid,
sp->status, status));
+
+ /*
+ * If the process continued,
+ * then update its status to running
+ * and mark the job running as well.
+ *
+ * If it was anything but running
+ * before, flag it as a change for
+ * reporting purposes later
+ */
if (WIFCONTINUED(status)) {
if (sp->status != -1)
jp->flags |= JOBCHANGED;
sp->status = -1;
jp->state = 0;
- } else
+ } else {
+ /* otherwise update status */
sp->status = status;
+ }
+
+ /*
+ * We now know the affected job
+ */
thisjob = jp;
if (changed != NULL)
*changed = jp;
}
+ /*
+ * After any update that might have just
+ * happened, if this process is running,
+ * the job is not stopped, or if the process
+ * simply stopped (not terminated) then the
+ * job is certainly not completed (done).
+ */
if (sp->status == -1)
stopped = 0;
else if (WIFSTOPPED(sp->status))
done = 0;
}
+
+ /*
+ * Once we have examined all processes for the
+ * job, if we still show it as stopped, then...
+ */
if (stopped) { /* stopped or done */
+ /*
+ * it might be stopped, or finished, decide:
+ */
int state = done ? JOBDONE : JOBSTOPPED;
+ /*
+ * If that wasn't the same as it was before
+ * then update its state, and if it just
+ * completed, make it be the current job (%%)
+ */
if (jp->state != state) {
VTRACE(DBG_JOBS,
("Job %d: changing state from %d to %d\n",
@@ -1388,6 +1491,15 @@
}
}
+ /*
+ * Now we have scanned all jobs. If we found the job that
+ * the process that changed state belonged to (we occasionally
+ * fork processes without associating them with a job, when one
+ * of those finishes, we simply ignore it, the zombie has been
+ * cleaned up, which is all that matters) then we need to
+ * determine if we should say something about it to stdout
+ */
+
if (thisjob &&
(thisjob->state != JOBRUNNING || thisjob->flags & JOBCHANGED)) {
int mode = 0;
@@ -1401,13 +1513,21 @@
showjob(out2, thisjob, mode);
else {
VTRACE(DBG_JOBS,
- ("Not printing status, rootshell=%d, job=%p\n",
- rootshell, job));
+ ("Not printing status for %p [%d], "
+ "mode=%#x rootshell=%d, job=%p [%d]\n",
+ thisjob, (thisjob ? (thisjob-jobtab+1) : 0),
+ mode, rootshell, job, (job ? (job-jobtab+1) : 0)));
thisjob->flags |= JOBCHANGED;
}
}
INTON;
+ /*
+ * Finally tell our caller that something happened (in general all
+ * anyone tests for is <= 0 (or >0) so the actual pid value here
+ * doesn't matter much, but we know it is >0 and we may as well
+ * give back something meaningful
+ */
return pid;
}
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