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envelope-from=vsementsov@virtuozzo.com; helo=EUR04-VI1-obe.outbound.protection.outlook.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/20 05:00:42 X-ACL-Warn: Detected OS = Windows NT kernel [generic] [fuzzy] X-Spam_score_int: -37 X-Spam_score: -3.8 X-Spam_bar: --- X-Spam_report: (-3.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, MSGID_FROM_MTA_HEADER=0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-1, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, URIBL_BLOCKED=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, vsementsov@virtuozzo.com, qemu-devel@nongnu.org, mreitz@redhat.com, den@openvz.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On shutdown nbd driver may be in a connecting state. We should shutdown it as well, otherwise we may hang in nbd_teardown_connection, waiting for conneciton_co to finish in BDRV_POLL_WHILE(bs, s->connection_co) loop if remote server is down. How to reproduce the dead lock: 1. Create nbd-fault-injector.conf with the following contents: [inject-error "mega1"] event=data io=readwrite when=before 2. In one terminal run nbd-fault-injector in a loop, like this: n=1; while true; do echo $n; ((n++)); ./nbd-fault-injector.py 127.0.0.1:10000 nbd-fault-injector.conf; done 3. In another terminal run qemu-io in a loop, like this: n=1; while true; do echo $n; ((n++)); ./qemu-io -c 'read 0 512' nbd+tcp://127.0.0.1:10000; done After some time, qemu-io will hang. Note, that this hang may be triggered by another bug, so the whole case is fixed only together with commit "block/nbd: allow drain during reconnect attempt". Signed-off-by: Vladimir Sementsov-Ogievskiy --- block/nbd.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/block/nbd.c b/block/nbd.c index 49254f1c3c..42146a26f7 100644 --- a/block/nbd.c +++ b/block/nbd.c @@ -206,11 +206,15 @@ static void nbd_teardown_connection(BlockDriverState *bs) { BDRVNBDState *s = (BDRVNBDState *)bs->opaque; - if (s->state == NBD_CLIENT_CONNECTED) { + if (s->ioc) { /* finish any pending coroutines */ - assert(s->ioc); qio_channel_shutdown(s->ioc, QIO_CHANNEL_SHUTDOWN_BOTH, NULL); + } else if (s->sioc) { + /* abort negotiation */ + qio_channel_shutdown(QIO_CHANNEL(s->sioc), QIO_CHANNEL_SHUTDOWN_BOTH, + NULL); } + s->state = NBD_CLIENT_QUIT; if (s->connection_co) { if (s->connection_co_sleep_ns_state) { @@ -1452,6 +1456,8 @@ static int nbd_client_connect(BlockDriverState *bs, Error **errp) return -ECONNREFUSED; } + s->sioc = sioc; + /* NBD handshake */ trace_nbd_client_connect(s->export); qio_channel_set_blocking(QIO_CHANNEL(sioc), false, NULL); @@ -1468,6 +1474,7 @@ static int nbd_client_connect(BlockDriverState *bs, Error **errp) g_free(s->info.name); if (ret < 0) { object_unref(OBJECT(sioc)); + s->sioc = NULL; return ret; } if (s->x_dirty_bitmap && !s->info.base_allocation) { @@ -1493,8 +1500,6 @@ static int nbd_client_connect(BlockDriverState *bs, Error **errp) } } - s->sioc = sioc; - if (!s->ioc) { s->ioc = QIO_CHANNEL(sioc); object_ref(OBJECT(s->ioc)); @@ -1515,6 +1520,7 @@ static int nbd_client_connect(BlockDriverState *bs, Error **errp) nbd_send_request(s->ioc ?: QIO_CHANNEL(sioc), &request); object_unref(OBJECT(sioc)); + s->sioc = NULL; return ret; } -- 2.21.0