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Daniel Thompson bdbc65eb77 HID: i2c-hid: goodix: Fix a lockdep splat commit `2787710f73` upstream. I'm was on the receiving end of a lockdep splat from this driver and after scratching my head I couldn't be entirely sure it was a false positive given we would also have to think about whether the regulator locking is safe (since the notifier is called whilst holding regulator locks which are also needed for regulator_is_enabled() ). Regardless of whether it is a real bug or not, the mutex isn't needed. We can use reference counting tricks instead to avoid races with the notifier calls. The observed splat follows: ------------------------------------------------------ kworker/u16:3/127 is trying to acquire lock: ffff00008021fb20 (&ihid_goodix->regulator_mutex){+.+.}-{4:4}, at: ihid_goodix_vdd_notify+0x30/0x94 but task is already holding lock: ffff0000835c60c0 (&(&rdev->notifier)->rwsem){++++}-{4:4}, at: blocking_notifier_call_chain+0x30/0x70 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&(&rdev->notifier)->rwsem){++++}-{4:4}: down_write+0x68/0x8c blocking_notifier_chain_register+0x54/0x70 regulator_register_notifier+0x1c/0x24 devm_regulator_register_notifier+0x58/0x98 i2c_hid_of_goodix_probe+0xdc/0x158 i2c_device_probe+0x25d/0x270 really_probe+0x174/0x2cc __driver_probe_device+0xc0/0xd8 driver_probe_device+0x50/0xe4 __device_attach_driver+0xa8/0xc0 bus_for_each_drv+0x9c/0xc0 __device_attach_async_helper+0x6c/0xbc async_run_entry_fn+0x38/0x100 process_one_work+0x294/0x438 worker_thread+0x180/0x258 kthread+0x120/0x130 ret_from_fork+0x10/0x20 -> #0 (&ihid_goodix->regulator_mutex){+.+.}-{4:4}: __lock_acquire+0xd24/0xfe8 lock_acquire+0x288/0x2f4 __mutex_lock+0xa0/0x338 mutex_lock_nested+0x3c/0x5c ihid_goodix_vdd_notify+0x30/0x94 notifier_call_chain+0x6c/0x8c blocking_notifier_call_chain+0x48/0x70 _notifier_call_chain.isra.0+0x18/0x20 _regulator_enable+0xc0/0x178 regulator_enable+0x40/0x7c goodix_i2c_hid_power_up+0x18/0x20 i2c_hid_core_power_up.isra.0+0x1c/0x2c i2c_hid_core_probe+0xd8/0x3d4 i2c_hid_of_goodix_probe+0x14c/0x158 i2c_device_probe+0x25c/0x270 really_probe+0x174/0x2cc __driver_probe_device+0xc0/0xd8 driver_probe_device+0x50/0xe4 __device_attach_driver+0xa8/0xc0 bus_for_each_drv+0x9c/0xc0 __device_attach_async_helper+0x6c/0xbc async_run_entry_fn+0x38/0x100 process_one_work+0x294/0x438 worker_thread+0x180/0x258 kthread+0x120/0x130 ret_from_fork+0x10/0x20 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&(&rdev->notifier)->rwsem); lock(&ihid_goodix->regulator_mutex); lock(&(&rdev->notifier)->rwsem); lock(&ihid_goodix->regulator_mutex); * DEADLOCK * Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> Fixes: `18eeef46d3` ("HID: i2c-hid: goodix: Tie the reset line to true state of the regulator") Reviewed-by: Douglas Anderson <dianders@chromium.org> Signed-off-by: Jiri Kosina <jkosina@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2022-02-23 12:03:03 +01:00
arch	parisc: Drop __init from map_pages declaration	2022-02-23 12:03:03 +01:00
block	block: bio-integrity: Advance seed correctly for larger interval sizes	2022-02-08 18:34:05 +01:00
certs	certs: Add support for using elliptic curve keys for signing modules	2021-08-23 19:55:42 +03:00
crypto	crypto: api - Move cryptomgr soft dependency into algapi	2022-02-11 09:10:26 +01:00
Documentation	ARM: dts: Fix timer regression for beagleboard revision c	2022-02-16 12:56:21 +01:00
drivers	HID: i2c-hid: goodix: Fix a lockdep splat	2022-02-23 12:03:03 +01:00
fs	btrfs: zoned: cache reported zone during mount	2022-02-23 12:03:02 +01:00
include	mm: memcg: synchronize objcg lists with a dedicated spinlock	2022-02-16 12:56:38 +01:00
init	init: make unknown command line param message clearer	2021-11-18 19:17:11 +01:00
ipc	ipc/sem: do not sleep with a spin lock held	2022-02-08 18:34:03 +01:00
kernel	perf: Fix list corruption in perf_cgroup_switch()	2022-02-16 12:56:41 +01:00
lib	lib/test_meminit: destroy cache in kmem_cache_alloc_bulk() test	2022-01-27 11:05:44 +01:00
LICENSES	LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes"	2021-07-15 06:31:24 -06:00
mm	mm: don't try to NUMA-migrate COW pages that have other uses	2022-02-23 12:03:03 +01:00
net	mptcp: netlink: process IPv6 addrs in creating listening sockets	2022-02-16 12:56:31 +01:00
samples	samples: bpf: Fix 'unknown warning group' build warning on Clang	2022-01-27 11:03:29 +01:00
scripts	Makefile.extrawarn: Move -Wunaligned-access to W=1	2022-02-16 12:56:39 +01:00
security	ima: Do not print policy rule with inactive LSM labels	2022-02-16 12:56:04 +01:00
sound	ASoC: codecs: wcd938x: fix return value of mixer put function	2022-02-08 18:34:11 +01:00
tools	selftests: netfilter: check stateless nat udp checksum fixup	2022-02-08 18:34:14 +01:00
usr	usr/include/Makefile: add linux/nfc.h to the compile-test coverage	2022-02-01 17:27:15 +01:00
virt	KVM: eventfd: Fix false positive RCU usage warning	2022-02-16 12:56:16 +01:00
.clang-format	clang-format: Update with the latest for_each macro list	2021-05-12 23:32:39 +02:00
.cocciconfig	scripts: add Linux .cocciconfig for coccinelle	2016-07-22 12:13:39 +02:00
.get_maintainer.ignore	Opt out of scripts/get_maintainer.pl	2019-05-16 10:53:40 -07:00
.gitattributes	.gitattributes: use 'dts' diff driver for dts files	2019-12-04 19:44:11 -08:00
.gitignore	.gitignore: ignore only top-level modules.builtin	2021-05-02 00:43:35 +09:00
.mailmap	mailmap: add Andrej Shadura	2021-10-18 20:22:03 -10:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	MAINTAINERS: Move Daniel Drake to credits	2021-09-21 08:34:58 +03:00
Kbuild	kbuild: rename hostprogs-y/always to hostprogs/always-y	2020-02-04 01:53:07 +09:00
Kconfig	kbuild: ensure full rebuild when the compiler is updated	2020-05-12 13:28:33 +09:00
MAINTAINERS	drm fixes for 5.15 final	2021-10-28 12:17:01 -07:00
Makefile	Linux 5.15.24	2022-02-16 12:56:41 +01:00
README	Drop all 00-INDEX files from Documentation/	2018-09-09 15:08:58 -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 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.