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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-BeenThere: stable@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: patches for DPDK stable branches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: stable-bounces@dpdk.org On 11/25/24 17:28, David Marchand wrote: > On Mon, Nov 25, 2024 at 5:20 PM Maxime Coquelin > wrote: >> On 11/25/24 12:14, David Marchand wrote: >>> On Mon, Nov 18, 2024 at 5:24 PM Stephen Hemminger >>> wrote: >>>> >>>> If lock is acquired for write, it must be released for write >>>> or a deadlock is likely. >>>> >>>> Bugzilla ID: 1582 >>>> Fixes: 9fc93a1e2320 ("vhost: fix virtqueue access check in datapath") >>>> Cc: david.marchand@redhat.com >>>> Cc: stable@dpdk.org >>>> >>>> Signed-off-by: Stephen Hemminger >>>> --- >>>> lib/vhost/virtio_net.c | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c >>>> index 298a5dae74..d764d4bc6a 100644 >>>> --- a/lib/vhost/virtio_net.c >>>> +++ b/lib/vhost/virtio_net.c >>>> @@ -2538,7 +2538,7 @@ virtio_dev_rx_async_submit(struct virtio_net *dev, struct vhost_virtqueue *vq, >>>> >>>> if (unlikely(!vq->access_ok)) { >>>> vhost_user_iotlb_rd_unlock(vq); >>>> - rte_rwlock_read_unlock(&vq->access_lock); >>>> + rte_rwlock_write_unlock(&vq->access_lock); >>> >>> A write lock is taken earlier, because virtio_dev_rx_async_submit_* >>> need it for access to vq->async (as opposed to the sync code that only >>> takes read lock). >>> >>> Here, no need to release/take again all locks. >>> A simpler fix is to directly call vring_translate(dev, vq). >>> >>> >> >> Ok, so both solutions are correct. >> >> David's one is more optimized, but this is a corner case in the async >> datapath so not really critical. >> >> On the other hand, Stephen's solution keeps the same pattern as the >> other datapaths. > > Ok, it avoids having a special case, and I prefer limiting special cases too. > > I'll send a RFC for new lock annotations (for catching such bug) for > the next release. Great, thanks for that! > >> >> I'd go with Stephen's solution, but would change the commit title to: >> >> vhost: fix deadlock in Rx async path >> >> With this change: >> >> Reviewed-by: Maxime Coquelin > > Yes, the title needed some work. > > Ack, will change while applying. Thanks, Maxime