Date: Tue, 29 Jan 2013 18:03:43 GMT From: Jukka Ukkonen <jau@iki.fi> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/175674: sem_open() should use O_EXLOCK with open() instead of a separate flock() call Message-ID: <201301291803.r0TI3h2A088948@red.freebsd.org> Resent-Message-ID: <201301291810.r0TIA1EZ084283@freefall.freebsd.org>
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>Number: 175674
>Category: kern
>Synopsis: sem_open() should use O_EXLOCK with open() instead of a separate flock() call
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: change-request
>Submitter-Id: current-users
>Arrival-Date: Tue Jan 29 18:10:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator: Jukka Ukkonen
>Release: 9.1-STABLE
>Organization:
-----
>Environment:
FreeBSD sleipnir 9.1-STABLE FreeBSD 9.1-STABLE #2 r246056M: Tue Jan 29 07:33:01 EET 2013 root@sleipnir:/usr/obj/usr/src/sys/Sleipnir amd64
>Description:
sem_open() is calling flock() to set a lock on a newly created file descriptor.
That is pointless. The open() call a few lines before the flock() could, and
in my opinion should, be done with the O_EXLOCK flag set.
>How-To-Repeat:
See "full description" above.
>Fix:
Simply apply the attached patch.
Notice, though, that the patch assumes kern/170369 has been applied first.
Patch attached with submission follows:
--- lib/libc/gen/sem_new.c.flock 2012-11-09 18:50:05.000000000 +0200
+++ lib/libc/gen/sem_new.c 2012-11-09 18:44:59.000000000 +0200
@@ -198,11 +198,13 @@
goto error;
}
- fd = _open(path, flags|O_RDWR|O_CLOEXEC, mode);
+ fd = _open(path, flags|O_RDWR|O_CLOEXEC|O_EXLOCK, mode);
if (fd == -1)
goto error;
+#if 0
if (flock(fd, LOCK_EX) == -1)
goto error;
+#endif
if (_fstat(fd, &sb)) {
flock(fd, LOCK_UN);
goto error;
>Release-Note:
>Audit-Trail:
>Unformatted:
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