Wed, May 22, 2024 at 10:52:19AM CEST, hengqi@xxxxxxxxxxxxxxxxx wrote: >On Wed, 22 May 2024 10:15:46 +0200, Jiri Pirko <jiri@xxxxxxxxxxx> wrote: >> Wed, May 22, 2024 at 05:45:48AM CEST, hengqi@xxxxxxxxxxxxxxxxx wrote: >> >This reverts commit 4d4ac2ececd3c42a08dd32a6e3a4aaf25f7efe44. >> >> This commit does not exist in -net or -net-next. > >It definitely exists in net-next :): >https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=4d4ac2ececd3c42a08dd32a6e3a4aaf25f7efe44 Correct. > >> >> > >> >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: >> > <TASK> >> > 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 <hengqi@xxxxxxxxxxxxxxxxx> >> >> Fixes tag missing. > >IIUC, > > "This reverts commit 4d4ac2ececd3c42a08dd32a6e3a4aaf25f7efe44." > >has provided a traceback way, which is not fixing other patches, >but fixing itself. So we do not need fixes tag. For submissions to -net, you always need the Fixes tag. As this fixes bug introduced by 4d4ac2ececd3c42a08dd32a6e3a4aaf25f7efe44, you should put that in "Fixes". > >Thanks. > >> >> >> >--- >> > 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 >> > >> >
