This is a note to let you know that I've just added the patch titled
net/mlx5e: Fix possible deadlock on mlx5e_tx_timeout_work
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-mlx5e-fix-possible-deadlock-on-mlx5e_tx_timeout_.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 7b37b802bc47c406fbcc8f22765052a9d1a5e4c2
Author: Moshe Shemesh <moshe@xxxxxxxxxx>
Date: Wed Sep 21 18:45:11 2022 +0300
net/mlx5e: Fix possible deadlock on mlx5e_tx_timeout_work
[ Upstream commit eab0da38912ebdad922ed0388209f7eb0a5163cd ]
Due to the cited patch, devlink health commands take devlink lock and
this may result in deadlock for mlx5e_tx_reporter as it takes local
state_lock before calling devlink health report and on the other hand
devlink health commands such as diagnose for same reporter take local
state_lock after taking devlink lock (see kernel log below).
To fix it, remove local state_lock from mlx5e_tx_timeout_work() before
calling devlink_health_report() and take care to cancel the work before
any call to close channels, which may free the SQs that should be
handled by the work. Before cancel_work_sync(), use current_work() to
check we are not calling it from within the work, as
mlx5e_tx_timeout_work() itself may close the channels and reopen as part
of recovery flow.
While removing state_lock from mlx5e_tx_timeout_work() keep rtnl_lock to
ensure no change in netdev->real_num_tx_queues, but use rtnl_trylock()
and a flag to avoid deadlock by calling cancel_work_sync() before
closing the channels while holding rtnl_lock too.
Kernel log:
======================================================
WARNING: possible circular locking dependency detected
6.0.0-rc3_for_upstream_debug_2022_08_30_13_10 #1 Not tainted
------------------------------------------------------
kworker/u16:2/65 is trying to acquire lock:
ffff888122f6c2f8 (&devlink->lock_key#2){+.+.}-{3:3}, at: devlink_health_report+0x2f1/0x7e0
but task is already holding lock:
ffff888121d20be0 (&priv->state_lock){+.+.}-{3:3}, at: mlx5e_tx_timeout_work+0x70/0x280 [mlx5_core]
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&priv->state_lock){+.+.}-{3:3}:
__mutex_lock+0x12c/0x14b0
mlx5e_rx_reporter_diagnose+0x71/0x700 [mlx5_core]
devlink_nl_cmd_health_reporter_diagnose_doit+0x212/0xa50
genl_family_rcv_msg_doit+0x1e9/0x2f0
genl_rcv_msg+0x2e9/0x530
netlink_rcv_skb+0x11d/0x340
genl_rcv+0x24/0x40
netlink_unicast+0x438/0x710
netlink_sendmsg+0x788/0xc40
sock_sendmsg+0xb0/0xe0
__sys_sendto+0x1c1/0x290
__x64_sys_sendto+0xdd/0x1b0
do_syscall_64+0x3d/0x90
entry_SYSCALL_64_after_hwframe+0x46/0xb0
-> #0 (&devlink->lock_key#2){+.+.}-{3:3}:
__lock_acquire+0x2c8a/0x6200
lock_acquire+0x1c1/0x550
__mutex_lock+0x12c/0x14b0
devlink_health_report+0x2f1/0x7e0
mlx5e_health_report+0xc9/0xd7 [mlx5_core]
mlx5e_reporter_tx_timeout+0x2ab/0x3d0 [mlx5_core]
mlx5e_tx_timeout_work+0x1c1/0x280 [mlx5_core]
process_one_work+0x7c2/0x1340
worker_thread+0x59d/0xec0
kthread+0x28f/0x330
ret_from_fork+0x1f/0x30
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&priv->state_lock);
lock(&devlink->lock_key#2);
lock(&priv->state_lock);
lock(&devlink->lock_key#2);
*** DEADLOCK ***
4 locks held by kworker/u16:2/65:
#0: ffff88811a55b138 ((wq_completion)mlx5e#2){+.+.}-{0:0}, at: process_one_work+0x6e2/0x1340
#1: ffff888101de7db8 ((work_completion)(&priv->tx_timeout_work)){+.+.}-{0:0}, at: process_one_work+0x70f/0x1340
#2: ffffffff84ce8328 (rtnl_mutex){+.+.}-{3:3}, at: mlx5e_tx_timeout_work+0x53/0x280 [mlx5_core]
#3: ffff888121d20be0 (&priv->state_lock){+.+.}-{3:3}, at: mlx5e_tx_timeout_work+0x70/0x280 [mlx5_core]
stack backtrace:
CPU: 1 PID: 65 Comm: kworker/u16:2 Not tainted 6.0.0-rc3_for_upstream_debug_2022_08_30_13_10 #1
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
Workqueue: mlx5e mlx5e_tx_timeout_work [mlx5_core]
Call Trace:
<TASK>
dump_stack_lvl+0x57/0x7d
check_noncircular+0x278/0x300
? print_circular_bug+0x460/0x460
? find_held_lock+0x2d/0x110
? __stack_depot_save+0x24c/0x520
? alloc_chain_hlocks+0x228/0x700
__lock_acquire+0x2c8a/0x6200
? register_lock_class+0x1860/0x1860
? kasan_save_stack+0x1e/0x40
? kasan_set_free_info+0x20/0x30
? ____kasan_slab_free+0x11d/0x1b0
? kfree+0x1ba/0x520
? devlink_health_do_dump.part.0+0x171/0x3a0
? devlink_health_report+0x3d5/0x7e0
lock_acquire+0x1c1/0x550
? devlink_health_report+0x2f1/0x7e0
? lockdep_hardirqs_on_prepare+0x400/0x400
? find_held_lock+0x2d/0x110
__mutex_lock+0x12c/0x14b0
? devlink_health_report+0x2f1/0x7e0
? devlink_health_report+0x2f1/0x7e0
? mutex_lock_io_nested+0x1320/0x1320
? trace_hardirqs_on+0x2d/0x100
? bit_wait_io_timeout+0x170/0x170
? devlink_health_do_dump.part.0+0x171/0x3a0
? kfree+0x1ba/0x520
? devlink_health_do_dump.part.0+0x171/0x3a0
devlink_health_report+0x2f1/0x7e0
mlx5e_health_report+0xc9/0xd7 [mlx5_core]
mlx5e_reporter_tx_timeout+0x2ab/0x3d0 [mlx5_core]
? lockdep_hardirqs_on_prepare+0x400/0x400
? mlx5e_reporter_tx_err_cqe+0x1b0/0x1b0 [mlx5_core]
? mlx5e_tx_reporter_timeout_dump+0x70/0x70 [mlx5_core]
? mlx5e_tx_reporter_dump_sq+0x320/0x320 [mlx5_core]
? mlx5e_tx_timeout_work+0x70/0x280 [mlx5_core]
? mutex_lock_io_nested+0x1320/0x1320
? process_one_work+0x70f/0x1340
? lockdep_hardirqs_on_prepare+0x400/0x400
? lock_downgrade+0x6e0/0x6e0
mlx5e_tx_timeout_work+0x1c1/0x280 [mlx5_core]
process_one_work+0x7c2/0x1340
? lockdep_hardirqs_on_prepare+0x400/0x400
? pwq_dec_nr_in_flight+0x230/0x230
? rwlock_bug.part.0+0x90/0x90
worker_thread+0x59d/0xec0
? process_one_work+0x1340/0x1340
kthread+0x28f/0x330
? kthread_complete_and_exit+0x20/0x20
ret_from_fork+0x1f/0x30
</TASK>
Fixes: c90005b5f75c ("devlink: Hold the instance lock in health callbacks")
Signed-off-by: Moshe Shemesh <moshe@xxxxxxxxxx>
Reviewed-by: Tariq Toukan <tariqt@xxxxxxxxxx>
Signed-off-by: Saeed Mahameed <saeedm@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h b/drivers/net/ethernet/mellanox/mlx5/core/en.h
index bc76fe6b06230..0ee456480a488 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
@@ -847,6 +847,7 @@ enum {
MLX5E_STATE_DESTROYING,
MLX5E_STATE_XDP_TX_ENABLED,
MLX5E_STATE_XDP_ACTIVE,
+ MLX5E_STATE_CHANNELS_ACTIVE,
};
struct mlx5e_modify_sq_param {
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 42e6f2fcf5f59..9910a0480f589 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -2586,6 +2586,7 @@ void mlx5e_close_channels(struct mlx5e_channels *chs)
{
int i;
+ ASSERT_RTNL();
if (chs->ptp) {
mlx5e_ptp_close(chs->ptp);
chs->ptp = NULL;
@@ -2865,17 +2866,29 @@ void mlx5e_activate_priv_channels(struct mlx5e_priv *priv)
if (mlx5e_is_vport_rep(priv))
mlx5e_rep_activate_channels(priv);
+ set_bit(MLX5E_STATE_CHANNELS_ACTIVE, &priv->state);
+
mlx5e_wait_channels_min_rx_wqes(&priv->channels);
if (priv->rx_res)
mlx5e_rx_res_channels_activate(priv->rx_res, &priv->channels);
}
+static void mlx5e_cancel_tx_timeout_work(struct mlx5e_priv *priv)
+{
+ WARN_ON_ONCE(test_bit(MLX5E_STATE_CHANNELS_ACTIVE, &priv->state));
+ if (current_work() != &priv->tx_timeout_work)
+ cancel_work_sync(&priv->tx_timeout_work);
+}
+
void mlx5e_deactivate_priv_channels(struct mlx5e_priv *priv)
{
if (priv->rx_res)
mlx5e_rx_res_channels_deactivate(priv->rx_res);
+ clear_bit(MLX5E_STATE_CHANNELS_ACTIVE, &priv->state);
+ mlx5e_cancel_tx_timeout_work(priv);
+
if (mlx5e_is_vport_rep(priv))
mlx5e_rep_deactivate_channels(priv);
@@ -4617,8 +4630,17 @@ static void mlx5e_tx_timeout_work(struct work_struct *work)
struct net_device *netdev = priv->netdev;
int i;
- rtnl_lock();
- mutex_lock(&priv->state_lock);
+ /* Take rtnl_lock to ensure no change in netdev->real_num_tx_queues
+ * through this flow. However, channel closing flows have to wait for
+ * this work to finish while holding rtnl lock too. So either get the
+ * lock or find that channels are being closed for other reason and
+ * this work is not relevant anymore.
+ */
+ while (!rtnl_trylock()) {
+ if (!test_bit(MLX5E_STATE_CHANNELS_ACTIVE, &priv->state))
+ return;
+ msleep(20);
+ }
if (!test_bit(MLX5E_STATE_OPENED, &priv->state))
goto unlock;
@@ -4637,7 +4659,6 @@ static void mlx5e_tx_timeout_work(struct work_struct *work)
}
unlock:
- mutex_unlock(&priv->state_lock);
rtnl_unlock();
}
