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.
>
>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.
>---
> 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
>
>
