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Date: Tue, 02 Jul 2013 13:28:56 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] qom: Use atomics for object refcounting
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To: =?ISO-8859-1?Q?Andreas_F=E4rber?= <afaerber@suse.de>
Cc: Jan Kiszka <jan.kiszka@siemens.com>, Liu Ping Fan <pingfank@linux.vnet.ibm.com>, qemu-devel <qemu-devel@nongnu.org>

Il 02/07/2013 13:15, Andreas F=E4rber ha scritto:
>> > @@ -683,16 +683,15 @@ GSList *object_class_get_list(const char *impl=
ements_type,
>> > =20
>> >  void object_ref(Object *obj)
>> >  {
>> > -    obj->ref++;
>> > +     __sync_fetch_and_add(&obj->ref, 1);
> How widespread are these in GCC/clang? Is there any fallback? I remembe=
r
> seeing some __sync_* warnings on Mac OS X around 4.2...

We are using them already in several places (vhost was the first one to
introduce them, I think, but now they are also in migration ad in some
tests too).  There is no fallback (asm could be a fallback, but we chose
to require GCC 4.2 or newer).

I'll change this to atomic_inc/dec when applying.  Otherwise

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Paolo