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Mon, 24 Aug 2020 15:27:01 +0000 (UTC) Date: Mon, 24 Aug 2020 16:26:59 +0100 From: Stefan Hajnoczi To: wanghonghao Subject: Re: [PATCH 1/2] QSLIST: add atomic replace operation Message-ID: <20200824152659.GA7124@stefanha-x1.localdomain> References: <20200824043121.13421-1-wanghonghao@bytedance.com> MIME-Version: 1.0 In-Reply-To: <20200824043121.13421-1-wanghonghao@bytedance.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=stefanha@redhat.com X-Mimecast-Spam-Score: 0.001 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="TB36FDmn/VVEgNH/" Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.120; envelope-from=stefanha@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/24 08:00:54 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.956, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, pbonzini@redhat.com, fam@euphon.net, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --TB36FDmn/VVEgNH/ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Aug 24, 2020 at 12:31:20PM +0800, wanghonghao wrote: > Replace a queue with another atomicly. It's useful when we need to transf= er > queues between threads. >=20 > Signed-off-by: wanghonghao > --- > include/qemu/queue.h | 4 ++++ > 1 file changed, 4 insertions(+) >=20 > diff --git a/include/qemu/queue.h b/include/qemu/queue.h > index 456a5b01ee..a3ff544193 100644 > --- a/include/qemu/queue.h > +++ b/include/qemu/queue.h > @@ -226,6 +226,10 @@ struct { = \ > (dest)->slh_first =3D atomic_xchg(&(src)->slh_first, NULL); = \ > } while (/*CONSTCOND*/0) > =20 > +#define QSLIST_REPLACE_ATOMIC(dest, src) do { = \ > + (src)->slh_first =3D atomic_xchg(&(dest)->slh_first, (src)->slh_= first); \ > +} while (/*CONSTCOND*/0) This is atomic for dest but not src. Maybe the name should make this clear: QSLIST_REPLACE_ATOMIC_DEST(). Please also add a doc comment mentioning that the modification to src is not atomic. 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