Date: Wed, 7 Mar 2007 08:20:09 GMT From: "Jukka A. Ukkonen" <jau@oxit.fi> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/109946: [kernel] [patch] Compatibility: FreeBSD has been missing WNOWAIT flag for wait*() calls://undefined Message-ID: <200703070820.l278K9Si055520@freefall.freebsd.org>
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The following reply was made to PR kern/109946; it has been noted by GNATS.
From: "Jukka A. Ukkonen" <jau@oxit.fi>
To: bug-followup@FreeBSD.org, jau@iki.fi
Cc:
Subject: Re: kern/109946: [kernel] [patch] Compatibility: FreeBSD has been
missing WNOWAIT flag for wait*() calls://undefined
Date: Wed, 07 Mar 2007 10:06:28 +0200
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Oops!
Reverse the if-condition to read
if (options & WNOWAIT) {
The version I attached seems to be an older diff
which I - obviously - cannot be using myself, because
doing the the wrong way would quickly end up never
cleaning the zombies away from the proc table.
I originally intended to do the test the other way
around enveloping the whole proc entry cleanup in
an if block, but then I decided to favour readability
and to cut the whole thing short by unlocking and
returning early.
The bad news is I made an intermediate diff for myself
while I had already added shortcut return but had not
yet reversed the if-test. Though I made another diff
after changing the if-test direction as well, I still
somehow managed to attach the wrong one to the PR. Sigh!
Additionally it might make sense to do the shortcut
return already before the "ptrace attach" test/block
but after the PROC_UNLOCK(p); line when rusage has
been filled in.
So, I attach a modified patch which in addition to
showing the proper WNOWAIT test also moves the WNOWAIT
test before the ptrace attach test.
Cheers,
// jau
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Content-Type: text/x-patch; name="wait-WNOWAIT.patch"; charset=iso-8859-1
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filename="wait-WNOWAIT.patch"
--- src/sys/sys/wait.h.orig Mon Mar 5 20:11:30 2007
+++ src/sys/sys/wait.h Mon Mar 5 20:40:32 2007
@@ -78,7 +78,9 @@
*/
#define WNOHANG 1 /* Don't hang in wait. */
#define WUNTRACED 2 /* Tell about stopped, untraced children. */
+#define WSTOPPED WUNTRACED /* SUS compatibility */
#define WCONTINUED 4 /* Report a job control continued process. */
+#define WNOWAIT 8 /* Poll only. Don't delete the proc entry. */
#if __BSD_VISIBLE
#define WLINUXCLONE 0x80000000 /* Wait for kthread spawned from linux_clone. */
--- src/sys/kern/kern_exit.c.orig Mon Mar 5 20:17:19 2007
+++ src/sys/kern/kern_exit.c Wed Mar 7 09:46:01 2007
@@ -590,7 +590,7 @@
pid = -q->p_pgid;
PROC_UNLOCK(q);
}
- if (options &~ (WUNTRACED|WNOHANG|WCONTINUED|WLINUXCLONE))
+ if (options &~ (WUNTRACED|WNOHANG|WCONTINUED|WNOWAIT|WLINUXCLONE))
return (EINVAL);
loop:
if (q->p_flag & P_STATCHILD) {
@@ -650,11 +650,32 @@
calcru(p, &rusage->ru_utime, &rusage->ru_stime);
}
+ PROC_UNLOCK(p);
+
+ if (options & WNOWAIT) {
+ /*
+ * SUS compatibility.
+ *
+ * We poll only returning the status.
+ * We do not wish to release the proc
+ * struct just yet.
+ * ==> If another thread created this
+ * process, it is sometimes better to
+ * leave this one as is for now and let
+ * the other thread reap the remnants
+ * of the child instead of automatically
+ * destroying the proc entry and making
+ * it impossible for the other thread to
+ * wait for its own child process.
+ */
+ sx_xunlock(&proctree_lock);
+ return (0);
+ }
+
/*
* If we got the child via a ptrace 'attach',
* we need to give it back to the old parent.
*/
- PROC_UNLOCK(p);
if (p->p_oppid && (t = pfind(p->p_oppid)) != NULL) {
PROC_LOCK(p);
p->p_oppid = 0;
--=_singer-1914-1173254800-0001-2--
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