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[78.80.19.19]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a5a1792228csm1749728566b.92.2024.05.22.01.15.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 May 2024 01:15:47 -0700 (PDT) Date: Wed, 22 May 2024 10:15:46 +0200 From: Jiri Pirko To: Heng Qi Cc: netdev@vger.kernel.org, virtualization@lists.linux.dev, Jason Wang , "Michael S. Tsirkin" , Xuan Zhuo , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Subject: Re: [PATCH net 2/2] Revert "virtio_net: Add a lock for per queue RX coalesce" Message-ID: References: <20240522034548.58131-1-hengqi@linux.alibaba.com> <20240522034548.58131-3-hengqi@linux.alibaba.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240522034548.58131-3-hengqi@linux.alibaba.com> Wed, May 22, 2024 at 05:45:48AM CEST, hengqi@linux.alibaba.com wrote: >This reverts commit 4d4ac2ececd3c42a08dd32a6e3a4aaf25f7efe44. This commit does not exist in -net or -net-next. > >When the following snippet is run, lockdep will complain[1]. > > /* Acquire all queues dim_locks */ > for (i = 0; i < vi->max_queue_pairs; i++) > mutex_lock(&vi->rq[i].dim_lock); > >At the same time, too many queues will cause lockdep to be more irritable, >which can be alleviated by using mutex_lock_nested(), however, there are >still new warning when the number of queues exceeds MAX_LOCKDEP_SUBCLASSES. >So I would like to gently revert this commit, although it brings >unsynchronization that is not so concerned: > 1. When dim is enabled, rx_dim_work may modify the coalescing parameters. > Users may read dirty coalescing parameters if querying. > 2. When dim is switched from enabled to disabled, a spurious dim worker > maybe scheduled, but this can be handled correctly by rx_dim_work. > >[1] >======================================================== >WARNING: possible recursive locking detected >6.9.0-rc7+ #319 Not tainted >-------------------------------------------- >ethtool/962 is trying to acquire lock: > >but task is already holding lock: > >other info that might help us debug this: >Possible unsafe locking scenario: > > CPU0 > ---- > lock(&vi->rq[i].dim_lock); > lock(&vi->rq[i].dim_lock); > >*** DEADLOCK *** > > May be due to missing lock nesting notation > >3 locks held by ethtool/962: > #0: ffffffff82dbaab0 (cb_lock){++++}-{3:3}, at: genl_rcv+0x19/0x40 > #1: ffffffff82dad0a8 (rtnl_mutex){+.+.}-{3:3}, at: > ethnl_default_set_doit+0xbe/0x1e0 > >stack backtrace: >CPU: 6 PID: 962 Comm: ethtool Not tainted 6.9.0-rc7+ #319 >Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS > rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 >Call Trace: > > dump_stack_lvl+0x79/0xb0 > check_deadlock+0x130/0x220 > __lock_acquire+0x861/0x990 > lock_acquire.part.0+0x72/0x1d0 > ? lock_acquire+0xf8/0x130 > __mutex_lock+0x71/0xd50 > virtnet_set_coalesce+0x151/0x190 > __ethnl_set_coalesce.isra.0+0x3f8/0x4d0 > ethnl_set_coalesce+0x34/0x90 > ethnl_default_set_doit+0xdd/0x1e0 > genl_family_rcv_msg_doit+0xdc/0x130 > genl_family_rcv_msg+0x154/0x230 > ? __pfx_ethnl_default_set_doit+0x10/0x10 > genl_rcv_msg+0x4b/0xa0 > ? __pfx_genl_rcv_msg+0x10/0x10 > netlink_rcv_skb+0x5a/0x110 > genl_rcv+0x28/0x40 > netlink_unicast+0x1af/0x280 > netlink_sendmsg+0x20e/0x460 > __sys_sendto+0x1fe/0x210 > ? find_held_lock+0x2b/0x80 > ? do_user_addr_fault+0x3a2/0x8a0 > ? __lock_release+0x5e/0x160 > ? do_user_addr_fault+0x3a2/0x8a0 > ? lock_release+0x72/0x140 > ? do_user_addr_fault+0x3a7/0x8a0 > __x64_sys_sendto+0x29/0x30 > do_syscall_64+0x78/0x180 > entry_SYSCALL_64_after_hwframe+0x76/0x7e > >Signed-off-by: Heng Qi Fixes tag missing. >--- > drivers/net/virtio_net.c | 53 +++++++++------------------------------- > 1 file changed, 12 insertions(+), 41 deletions(-) > >diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c >index 1cad06cef230..e4a1dff2a64a 100644 >--- a/drivers/net/virtio_net.c >+++ b/drivers/net/virtio_net.c >@@ -316,9 +316,6 @@ struct receive_queue { > /* Is dynamic interrupt moderation enabled? */ > bool dim_enabled; > >- /* Used to protect dim_enabled and inter_coal */ >- struct mutex dim_lock; >- > /* Dynamic Interrupt Moderation */ > struct dim dim; > >@@ -2368,10 +2365,6 @@ static int virtnet_poll(struct napi_struct *napi, int budget) > /* Out of packets? */ > if (received < budget) { > napi_complete = virtqueue_napi_complete(napi, rq->vq, received); >- /* Intentionally not taking dim_lock here. This may result in a >- * spurious net_dim call. But if that happens virtnet_rx_dim_work >- * will not act on the scheduled work. >- */ > if (napi_complete && rq->dim_enabled) > virtnet_rx_dim_update(vi, rq); > } >@@ -3247,11 +3240,9 @@ static int virtnet_set_ringparam(struct net_device *dev, > return err; > > /* The reason is same as the transmit virtqueue reset */ >- mutex_lock(&vi->rq[i].dim_lock); > err = virtnet_send_rx_ctrl_coal_vq_cmd(vi, i, > vi->intr_coal_rx.max_usecs, > vi->intr_coal_rx.max_packets); >- mutex_unlock(&vi->rq[i].dim_lock); > if (err) > return err; > } >@@ -4257,7 +4248,6 @@ static int virtnet_send_rx_notf_coal_cmds(struct virtnet_info *vi, > struct virtio_net_ctrl_coal_rx *coal_rx __free(kfree) = NULL; > bool rx_ctrl_dim_on = !!ec->use_adaptive_rx_coalesce; > struct scatterlist sgs_rx; >- int ret = 0; > int i; > > if (rx_ctrl_dim_on && !virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL)) >@@ -4267,22 +4257,16 @@ static int virtnet_send_rx_notf_coal_cmds(struct virtnet_info *vi, > ec->rx_max_coalesced_frames != vi->intr_coal_rx.max_packets)) > return -EINVAL; > >- /* Acquire all queues dim_locks */ >- for (i = 0; i < vi->max_queue_pairs; i++) >- mutex_lock(&vi->rq[i].dim_lock); >- > if (rx_ctrl_dim_on && !vi->rx_dim_enabled) { > vi->rx_dim_enabled = true; > for (i = 0; i < vi->max_queue_pairs; i++) > vi->rq[i].dim_enabled = true; >- goto unlock; >+ return 0; > } > > coal_rx = kzalloc(sizeof(*coal_rx), GFP_KERNEL); >- if (!coal_rx) { >- ret = -ENOMEM; >- goto unlock; >- } >+ if (!coal_rx) >+ return -ENOMEM; > > if (!rx_ctrl_dim_on && vi->rx_dim_enabled) { > vi->rx_dim_enabled = false; >@@ -4300,10 +4284,8 @@ static int virtnet_send_rx_notf_coal_cmds(struct virtnet_info *vi, > > if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL, > VIRTIO_NET_CTRL_NOTF_COAL_RX_SET, >- &sgs_rx)) { >- ret = -EINVAL; >- goto unlock; >- } >+ &sgs_rx)) >+ return -EINVAL; > > vi->intr_coal_rx.max_usecs = ec->rx_coalesce_usecs; > vi->intr_coal_rx.max_packets = ec->rx_max_coalesced_frames; >@@ -4311,11 +4293,8 @@ static int virtnet_send_rx_notf_coal_cmds(struct virtnet_info *vi, > vi->rq[i].intr_coal.max_usecs = ec->rx_coalesce_usecs; > vi->rq[i].intr_coal.max_packets = ec->rx_max_coalesced_frames; > } >-unlock: >- for (i = vi->max_queue_pairs - 1; i >= 0; i--) >- mutex_unlock(&vi->rq[i].dim_lock); > >- return ret; >+ return 0; > } > > static int virtnet_send_notf_coal_cmds(struct virtnet_info *vi, >@@ -4339,24 +4318,19 @@ static int virtnet_send_rx_notf_coal_vq_cmds(struct virtnet_info *vi, > u16 queue) > { > bool rx_ctrl_dim_on = !!ec->use_adaptive_rx_coalesce; >+ bool cur_rx_dim = vi->rq[queue].dim_enabled; > u32 max_usecs, max_packets; >- bool cur_rx_dim; > int err; > >- mutex_lock(&vi->rq[queue].dim_lock); >- cur_rx_dim = vi->rq[queue].dim_enabled; > max_usecs = vi->rq[queue].intr_coal.max_usecs; > max_packets = vi->rq[queue].intr_coal.max_packets; > > if (rx_ctrl_dim_on && (ec->rx_coalesce_usecs != max_usecs || >- ec->rx_max_coalesced_frames != max_packets)) { >- mutex_unlock(&vi->rq[queue].dim_lock); >+ ec->rx_max_coalesced_frames != max_packets)) > return -EINVAL; >- } > > if (rx_ctrl_dim_on && !cur_rx_dim) { > vi->rq[queue].dim_enabled = true; >- mutex_unlock(&vi->rq[queue].dim_lock); > return 0; > } > >@@ -4369,8 +4343,10 @@ static int virtnet_send_rx_notf_coal_vq_cmds(struct virtnet_info *vi, > err = virtnet_send_rx_ctrl_coal_vq_cmd(vi, queue, > ec->rx_coalesce_usecs, > ec->rx_max_coalesced_frames); >- mutex_unlock(&vi->rq[queue].dim_lock); >- return err; >+ if (err) >+ return err; >+ >+ return 0; > } > > static int virtnet_send_notf_coal_vq_cmds(struct virtnet_info *vi, >@@ -4404,7 +4380,6 @@ static void virtnet_rx_dim_work(struct work_struct *work) > > qnum = rq - vi->rq; > >- mutex_lock(&rq->dim_lock); > if (!rq->dim_enabled) > goto out; > >@@ -4420,7 +4395,6 @@ static void virtnet_rx_dim_work(struct work_struct *work) > } > out: > dim->state = DIM_START_MEASURE; >- mutex_unlock(&rq->dim_lock); > } > > static int virtnet_coal_params_supported(struct ethtool_coalesce *ec) >@@ -4558,13 +4532,11 @@ static int virtnet_get_per_queue_coalesce(struct net_device *dev, > return -EINVAL; > > if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL)) { >- mutex_lock(&vi->rq[queue].dim_lock); > ec->rx_coalesce_usecs = vi->rq[queue].intr_coal.max_usecs; > ec->tx_coalesce_usecs = vi->sq[queue].intr_coal.max_usecs; > ec->tx_max_coalesced_frames = vi->sq[queue].intr_coal.max_packets; > ec->rx_max_coalesced_frames = vi->rq[queue].intr_coal.max_packets; > ec->use_adaptive_rx_coalesce = vi->rq[queue].dim_enabled; >- mutex_unlock(&vi->rq[queue].dim_lock); > } else { > ec->rx_max_coalesced_frames = 1; > >@@ -5396,7 +5368,6 @@ static int virtnet_alloc_queues(struct virtnet_info *vi) > > u64_stats_init(&vi->rq[i].stats.syncp); > u64_stats_init(&vi->sq[i].stats.syncp); >- mutex_init(&vi->rq[i].dim_lock); > } > > return 0; >-- >2.32.0.3.g01195cf9f > >