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Jacob Keller c6124f6fd3 iavf: fix circular lock dependency with netdev_lock 
We have recently seen reports of lockdep circular lock dependency warnings
when loading the iAVF driver:

[ 1504.790308] ======================================================
[ 1504.790309] WARNING: possible circular locking dependency detected
[ 1504.790310] 6.13.0 #net_next_rt.c2933b2befe2.el9 Not tainted
[ 1504.790311] ------------------------------------------------------
[ 1504.790312] kworker/u128:0/13566 is trying to acquire lock:
[ 1504.790313] ffff97d0e4738f18 (&dev->lock){+.+.}-{4:4}, at: register_netdevice+0x52c/0x710
[ 1504.790320]
[ 1504.790320] but task is already holding lock:
[ 1504.790321] ffff97d0e47392e8 (&adapter->crit_lock){+.+.}-{4:4}, at: iavf_finish_config+0x37/0x240 [iavf]
[ 1504.790330]
[ 1504.790330] which lock already depends on the new lock.
[ 1504.790330]
[ 1504.790330]
[ 1504.790330] the existing dependency chain (in reverse order) is:
[ 1504.790331]
[ 1504.790331] -> #1 (&adapter->crit_lock){+.+.}-{4:4}:
[ 1504.790333]        __lock_acquire+0x52d/0xbb0
[ 1504.790337]        lock_acquire+0xd9/0x330
[ 1504.790338]        mutex_lock_nested+0x4b/0xb0
[ 1504.790341]        iavf_finish_config+0x37/0x240 [iavf]
[ 1504.790347]        process_one_work+0x248/0x6d0
[ 1504.790350]        worker_thread+0x18d/0x330
[ 1504.790352]        kthread+0x10e/0x250
[ 1504.790354]        ret_from_fork+0x30/0x50
[ 1504.790357]        ret_from_fork_asm+0x1a/0x30
[ 1504.790361]
[ 1504.790361] -> #0 (&dev->lock){+.+.}-{4:4}:
[ 1504.790364]        check_prev_add+0xf1/0xce0
[ 1504.790366]        validate_chain+0x46a/0x570
[ 1504.790368]        __lock_acquire+0x52d/0xbb0
[ 1504.790370]        lock_acquire+0xd9/0x330
[ 1504.790371]        mutex_lock_nested+0x4b/0xb0
[ 1504.790372]        register_netdevice+0x52c/0x710
[ 1504.790374]        iavf_finish_config+0xfa/0x240 [iavf]
[ 1504.790379]        process_one_work+0x248/0x6d0
[ 1504.790381]        worker_thread+0x18d/0x330
[ 1504.790383]        kthread+0x10e/0x250
[ 1504.790385]        ret_from_fork+0x30/0x50
[ 1504.790387]        ret_from_fork_asm+0x1a/0x30
[ 1504.790389]
[ 1504.790389] other info that might help us debug this:
[ 1504.790389]
[ 1504.790389]  Possible unsafe locking scenario:
[ 1504.790389]
[ 1504.790390]        CPU0                    CPU1
[ 1504.790391]        ----                    ----
[ 1504.790391]   lock(&adapter->crit_lock);
[ 1504.790393]                                lock(&dev->lock);
[ 1504.790394]                                lock(&adapter->crit_lock);
[ 1504.790395]   lock(&dev->lock);
[ 1504.790397]
[ 1504.790397]  *** DEADLOCK ***

This appears to be caused by the change in commit 5fda3f3534 ("net: make
netdev_lock() protect netdev->reg_state"), which added a netdev_lock() in
register_netdevice.

The iAVF driver calls register_netdevice() from iavf_finish_config(), as a
final stage of its state machine post-probe. It currently takes the RTNL
lock, then the netdev lock, and then the device critical lock. This pattern
is used throughout the driver. Thus there is a strong dependency that the
crit_lock should not be acquired before the net device lock. The change to
register_netdevice creates an ABBA lock order violation because the iAVF
driver is holding the crit_lock while calling register_netdevice, which
then takes the netdev_lock.

It seems likely that future refactors could result in netdev APIs which
hold the netdev_lock while calling into the driver. This means that we
should not re-order the locks so that netdev_lock is acquired after the
device private crit_lock.

Instead, notice that we already release the netdev_lock prior to calling
the register_netdevice. This flow only happens during the early driver
initialization as we transition through the __IAVF_STARTUP,
__IAVF_INIT_VERSION_CHECK, __IAVF_INIT_GET_RESOURCES, etc.

Analyzing the places where we take crit_lock in the driver there are two
sources:

a) several of the work queue tasks including adminq_task, watchdog_task,
reset_task, and the finish_config task.

b) various callbacks which ultimately stem back to .ndo operations or
ethtool operations.

The latter cannot be triggered until after the netdevice registration is
completed successfully.

The iAVF driver uses alloc_ordered_workqueue, which is an unbound workqueue
that has a max limit of 1, and thus guarantees that only a single work item
on the queue is executing at any given time, so none of the other work
threads could be executing due to the ordered workqueue guarantees.

The iavf_finish_config() function also does not do anything else after
register_netdevice, unless it fails. It seems unlikely that the driver
private crit_lock is protecting anything that register_netdevice() itself
touches.

Thus, to fix this ABBA lock violation, lets simply release the
adapter->crit_lock as well as netdev_lock prior to calling
register_netdevice(). We do still keep holding the RTNL lock as required by
the function. If we do fail to register the netdevice, then we re-acquire
the adapter critical lock to finish the transition back to
__IAVF_INIT_CONFIG_ADAPTER.

This ensures every call where both netdev_lock and the adapter->crit_lock
are acquired under the same ordering.

Fixes: afc664987a ("eth: iavf: extend the netdev_lock usage")
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Tested-by: Rafal Romanowski <rafal.romanowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://patch.msgid.link/20250224190647.3601930-5-anthony.l.nguyen@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2025-02-25 19:09:40 -08:00
arch powerpc fixes for 6.14 #3 2025-02-17 10:32:19 -08:00
block block-6.14-20250214 2025-02-14 11:40:59 -08:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
Documentation MAINTAINERS: update Nick's contact info 2025-02-17 22:40:04 -08:00
drivers iavf: fix circular lock dependency with netdev_lock 2025-02-25 19:09:40 -08:00
fs afs: Give an afs_server object a ref on the afs_cell object it points to 2025-02-21 15:06:29 -08:00
include tcp: devmem: don't write truncated dmabuf CMSGs to userspace 2025-02-25 18:15:43 -08:00
init Kbuild updates for v6.14 2025-01-31 12:07:07 -08:00
io_uring io_uring-6.14-20250214 2025-02-14 11:30:53 -08:00
ipc treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
kernel vfs-6.14-rc4.fixes 2025-02-17 10:38:25 -08:00
lib test_xarray: fix failure in check_pause when CONFIG_XARRAY_MULTI is not defined 2025-02-17 22:40:04 -08:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm kasan: don't call find_vm_area() in a PREEMPT_RT kernel 2025-02-17 22:40:04 -08:00
net mptcp: safety check before fallback 2025-02-25 18:34:37 -08:00
rust Driver core api addition for 6.14-rc3 2025-02-16 12:54:42 -08:00
samples Driver core api addition for 6.14-rc3 2025-02-16 12:54:42 -08:00
scripts modpost: Fix a few typos in a comment 2025-02-16 03:10:58 +09:00
security Redo of pathname patternization and fix spelling errors. 2025-02-11 10:19:36 -08:00
sound ALSA: seq: Drop UMP events when no UMP-conversion is set 2025-02-17 18:02:02 +01:00
tools selftests: drv-net: test XDP, HDS auto and the ioctl path 2025-02-24 14:16:37 -08:00
usr kbuild: Drop support for include/asm-<arch> in headers_check.pl 2024-12-21 11:43:17 +09:00
virt KVM: remove kvm_arch_post_init_vm 2025-02-04 11:27:45 -05:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: give Clippy the minimum supported Rust version 2025-01-10 00:17:25 +01:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: use host dylib naming convention to support macOS 2025-01-10 01:01:24 +01:00
.mailmap mailmap: update Nick's entry 2025-02-17 22:40:03 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING
CREDITS MAINTAINERS: Move Pavel to kernel.org address 2025-02-07 09:12:33 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: socket timestamping: add Jason Xing as reviewer 2025-02-25 13:26:27 +01:00
Makefile Linux 6.14-rc3 2025-02-16 14:02:44 -08:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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 reStructuredText 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.