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bh=g5U/U6h9vjsb1p1rSaKlfb5FTQwoOb61k678GR2Ee94=; b=Hm4YQxfm1Hdcf94aI8bBZ+CkCOEGCooKoGdpan3xntRIayKZoHWzdvDV/eu6BH3D22mKTj d1JF3FdK7G7TD5ismjZit1CMuPGfexX3LhEmvhqRHem7nCwKIC29qWTNYbzggnyQ+pIBsq WBROBn/jkkZXP45OjL+Wh7fCu679q9s= X-MC-Unique: LRawtiKJPbKCzTiDmrQ06A-1 From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, qemu-devel@nongnu.org Subject: [PULL 4/9] stream: Fix AioContext locking during bdrv_graph_wrlock() Date: Tue, 21 Nov 2023 12:52:57 +0100 Message-ID: <20231121115302.52214-5-kwolf@redhat.com> In-Reply-To: <20231121115302.52214-1-kwolf@redhat.com> References: <20231121115302.52214-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.035, 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1700567644770100001 Content-Type: text/plain; charset="utf-8" In stream_prepare(), we need to temporarily drop the AioContext lock that job_prepare_locked() took for us while calling the graph write lock functions which can poll. All block nodes related to this block job are in the same AioContext, so we can pass any of them to bdrv_graph_wrlock()/ bdrv_graph_wrunlock(). Unfortunately, the one that we picked is base, which can be NULL - and in this case the AioContext lock is not released and deadlocks can occur. Fix this by passing s->target_bs, which is never NULL. Signed-off-by: Kevin Wolf Message-ID: <20231115172012.112727-4-kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf --- block/stream.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/block/stream.c b/block/stream.c index e3aa696289..01fe7c0f16 100644 --- a/block/stream.c +++ b/block/stream.c @@ -99,9 +99,9 @@ static int stream_prepare(Job *job) } } =20 - bdrv_graph_wrlock(base); + bdrv_graph_wrlock(s->target_bs); bdrv_set_backing_hd_drained(unfiltered_bs, base, &local_err); - bdrv_graph_wrunlock(base); + bdrv_graph_wrunlock(s->target_bs); =20 /* * This call will do I/O, so the graph can change again from here = on. --=20 2.42.0