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Linux kernel source tree
eab0da3891
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:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.