From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:47889) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Rqj0k-0000KR-Pi for qemu-devel@nongnu.org; Fri, 27 Jan 2012 05:26:32 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Rqj0f-0005lM-7P for qemu-devel@nongnu.org; Fri, 27 Jan 2012 05:26:26 -0500 Date: Fri, 27 Jan 2012 10:26:06 +0000 From: "Daniel P. Berrange" Message-ID: <20120127102606.GC6522@redhat.com> References: <1327613801-5828-1-git-send-email-lersek@redhat.com> <20120127063639.GA22748@stefanha-thinkpad.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20120127063639.GA22748@stefanha-thinkpad.localdomain> Subject: Re: [Qemu-devel] [Qemu-trivial] [PATCH] keep the PID file locked for the lifetime of the process Reply-To: "Daniel P. Berrange" List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: qemu-trivial@nongnu.org, Laszlo Ersek , qemu-devel@nongnu.org On Fri, Jan 27, 2012 at 06:36:39AM +0000, Stefan Hajnoczi wrote: > On Thu, Jan 26, 2012 at 10:36:41PM +0100, Laszlo Ersek wrote: > > The lockf() call in qemu_create_pidfile() aims at ensuring mutual > > exclusion. We shouldn't close the pidfile on success, because that drops > > the lock as well [1]: > > > > "File locks shall be released on first close by the locking process > > of any file descriptor for the file." > > > > Coverity may complain again about the leaked file descriptor; let's > > worry about that later. > > > > [1] http://pubs.opengroup.org/onlinepubs/9699919799/functions/lockf.html > > > > Signed-off-by: Laszlo Ersek > > --- > > Isn't the normal way to do pidfiles O_CREAT | O_EXCL? It may not work > on all NFS versions but putting the pidfile on NFS doesn't really make > sense. > > Then we can drop the lockf(3) completely. IMHO it is preferable to use lockf because that makes sure you are crash safe, so you don't get later bogus startup failures due to stale pidfiles Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|