From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57400) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Uu2aj-0004EQ-Ip for qemu-devel@nongnu.org; Tue, 02 Jul 2013 11:34:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Uu2ah-0000Zy-Hh for qemu-devel@nongnu.org; Tue, 02 Jul 2013 11:34:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:17293) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Uu2ah-0000Zm-8C for qemu-devel@nongnu.org; Tue, 02 Jul 2013 11:34:03 -0400 Message-ID: <51D2F2D5.90801@redhat.com> Date: Tue, 02 Jul 2013 17:33:41 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <51D29F27.9040706@siemens.com> <87bo6lqarq.fsf@codemonkey.ws> In-Reply-To: <87bo6lqarq.fsf@codemonkey.ws> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] qom: Use atomics for object refcounting List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Jan Kiszka , Liu Ping Fan , qemu-devel Il 02/07/2013 16:47, Anthony Liguori ha scritto: > Jan Kiszka writes: > >> Objects can soon be referenced/dereference outside the BQL. So we need >> to use atomics in object_ref/unref. >> >> Based on patch by Liu Ping Fan. >> >> Signed-off-by: Jan Kiszka >> --- >> qom/object.c | 5 ++--- >> 1 files changed, 2 insertions(+), 3 deletions(-) >> >> diff --git a/qom/object.c b/qom/object.c >> index 803b94b..a76a30b 100644 >> --- a/qom/object.c >> +++ b/qom/object.c >> @@ -683,16 +683,15 @@ GSList *object_class_get_list(const char *implements_type, >> >> void object_ref(Object *obj) >> { >> - obj->ref++; >> + __sync_fetch_and_add(&obj->ref, 1); >> } >> >> void object_unref(Object *obj) >> { >> g_assert(obj->ref > 0); >> - obj->ref--; >> >> /* parent always holds a reference to its children */ >> - if (obj->ref == 0) { >> + if (__sync_sub_and_fetch(&obj->ref, 1) == 0) { >> object_finalize(obj); >> } >> } > > Should we introduce something akin to kref now that referencing counting > has gotten fancy? I'm not a big fan of kref (it seems _too_ thin a wrapper to me, i.e. it doesn't really wrap enough to be useful), but I wouldn't oppose it if someone else does it. Paolo