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Johan Hovold ea77e9b9fb scsi: ufs: core: Fix devfreq deadlocks commit `ba81043753` upstream. There is a lock inversion and rwsem read-lock recursion in the devfreq target callback which can lead to deadlocks. Specifically, ufshcd_devfreq_scale() already holds a clk_scaling_lock read lock when toggling the write booster, which involves taking the dev_cmd mutex before taking another clk_scaling_lock read lock. This can lead to a deadlock if another thread: 1) tries to acquire the dev_cmd and clk_scaling locks in the correct order, or 2) takes a clk_scaling write lock before the attempt to take the clk_scaling read lock a second time. Fix this by dropping the clk_scaling_lock before toggling the write booster as was done before commit `0e9d4ca43b` ("scsi: ufs: Protect some contexts from unexpected clock scaling"). While the devfreq callbacks are already serialised, add a second serialising mutex to handle the unlikely case where a callback triggered through the devfreq sysfs interface is racing with a request to disable clock scaling through the UFS controller 'clkscale_enable' sysfs attribute. This could otherwise lead to the write booster being left disabled after having disabled clock scaling. Also take the new mutex in ufshcd_clk_scaling_allow() to make sure that any pending write booster update has completed on return. Note that this currently only affects Qualcomm platforms since commit `87bd05016a` ("scsi: ufs: core: Allow host driver to disable wb toggling during clock scaling"). The lock inversion (i.e. 1 above) was reported by lockdep as: ====================================================== WARNING: possible circular locking dependency detected 6.1.0-next-20221216 #211 Not tainted ------------------------------------------------------ kworker/u16:2/71 is trying to acquire lock: ffff076280ba98a0 (&hba->dev_cmd.lock){+.+.}-{3:3}, at: ufshcd_query_flag+0x50/0x1c0 but task is already holding lock: ffff076280ba9cf0 (&hba->clk_scaling_lock){++++}-{3:3}, at: ufshcd_devfreq_scale+0x2b8/0x380 which lock already depends on the new lock. [ +0.011606] the existing dependency chain (in reverse order) is: -> #1 (&hba->clk_scaling_lock){++++}-{3:3}: lock_acquire+0x68/0x90 down_read+0x58/0x80 ufshcd_exec_dev_cmd+0x70/0x2c0 ufshcd_verify_dev_init+0x68/0x170 ufshcd_probe_hba+0x398/0x1180 ufshcd_async_scan+0x30/0x320 async_run_entry_fn+0x34/0x150 process_one_work+0x288/0x6c0 worker_thread+0x74/0x450 kthread+0x118/0x120 ret_from_fork+0x10/0x20 -> #0 (&hba->dev_cmd.lock){+.+.}-{3:3}: __lock_acquire+0x12a0/0x2240 lock_acquire.part.0+0xcc/0x220 lock_acquire+0x68/0x90 __mutex_lock+0x98/0x430 mutex_lock_nested+0x2c/0x40 ufshcd_query_flag+0x50/0x1c0 ufshcd_query_flag_retry+0x64/0x100 ufshcd_wb_toggle+0x5c/0x120 ufshcd_devfreq_scale+0x2c4/0x380 ufshcd_devfreq_target+0xf4/0x230 devfreq_set_target+0x84/0x2f0 devfreq_update_target+0xc4/0xf0 devfreq_monitor+0x38/0x1f0 process_one_work+0x288/0x6c0 worker_thread+0x74/0x450 kthread+0x118/0x120 ret_from_fork+0x10/0x20 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&hba->clk_scaling_lock); lock(&hba->dev_cmd.lock); lock(&hba->clk_scaling_lock); lock(&hba->dev_cmd.lock); * DEADLOCK * Fixes: `0e9d4ca43b` ("scsi: ufs: Protect some contexts from unexpected clock scaling") Cc: stable@vger.kernel.org # 5.12 Cc: Can Guo <quic_cang@quicinc.com> Tested-by: Andrew Halaney <ahalaney@redhat.com> Signed-off-by: Johan Hovold <johan+linaro@kernel.org> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Link: https://lore.kernel.org/r/20230116161201.16923-1-johan+linaro@kernel.org Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		History 2023-02-01 08:34:39 +01:00
arch	KVM: arm64: GICv4.1: Fix race with doorbell on VPE activation/deactivation	2023-02-01 08:34:39 +01:00
block	block: mq-deadline: Rename deadline_is_seq_writes()	2023-01-24 07:24:44 +01:00
certs	certs: make system keyring depend on built-in x509 parser	2022-09-24 04:31:18 +09:00
crypto	crypto: tcrypt - Fix multibuffer skcipher speed test mem leak	2022-12-31 13:32:34 +01:00
Documentation	docs: Fix path paste-o for /sys/kernel/warn_count	2023-01-24 07:24:41 +01:00
drivers
fs	ovl: fail on invalid uid/gid mapping at copy up	2023-02-01 08:34:38 +01:00
include
init	gcc: disable -Warray-bounds for gcc-11 too	2023-01-14 10:33:43 +01:00
io_uring	io_uring/net: cache provided buffer group value for multishot receives	2023-02-01 08:34:38 +01:00
ipc	ipc: fix memory leak in init_mqueue_fs()	2022-12-31 13:32:01 +01:00
kernel	trace_events_hist: add check for return value of 'create_hist_field'	2023-02-01 08:34:37 +01:00
lib	lockref: stop doing cpu_relax in the cmpxchg loop	2023-02-01 08:34:34 +01:00
LICENSES	LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers	2021-12-16 14:33:10 +01:00
mm	panic: Consolidate open-coded panic_on_warn checks	2023-01-24 07:24:41 +01:00
net	wifi: mac80211: Fix iTXQ AMPDU fragmentation handling	2023-02-01 08:34:36 +01:00
rust	Kbuild: add Rust support	2022-09-28 09:02:20 +02:00
samples	ftrace: Export ftrace_free_filter() to modules	2023-02-01 08:34:37 +01:00
scripts	ftrace/scripts: Update the instructions for ftrace-bisect.sh	2023-02-01 08:34:37 +01:00
security	tomoyo: fix broken dependency on *.conf.default	2023-02-01 08:34:06 +01:00
sound	ASoC: fsl-asoc-card: Fix naming of AC'97 CODEC widgets	2023-02-01 08:34:31 +01:00
tools	Revert "selftests/bpf: check null propagation only neither reg is PTR_TO_BTF_ID"	2023-02-01 08:34:34 +01:00
usr	usr/gen_init_cpio.c: remove unnecessary -1 values from int file	2022-10-03 14:21:44 -07:00
virt	kvm/vfio: Fix potential deadlock on vfio group_lock	2023-02-01 08:34:36 +01:00
.clang-format	inet: ping: use hlist_nulls rcu iterator during lookup	2022-12-01 12:42:46 +01:00
.cocciconfig	scripts: add Linux .cocciconfig for coccinelle	2016-07-22 12:13:39 +02:00
.get_maintainer.ignore	get_maintainer: add Alan to .get_maintainer.ignore	2022-08-20 15:17:44 -07:00
.gitattributes	.gitattributes: use 'dts' diff driver for dts files	2019-12-04 19:44:11 -08:00
.gitignore	Kbuild: add Rust support	2022-09-28 09:02:20 +02:00
.mailmap	9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address	2022-12-10 17:10:52 -08:00
.rustfmt.toml	rust: add `.rustfmt.toml`	2022-09-28 09:02:20 +02:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	MAINTAINERS: Remove Michal Marek from Kbuild maintainers	2022-11-16 14:53:00 +09:00
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	panic: Expose "warn_count" to sysfs	2023-01-24 07:24:41 +01:00
Makefile	kbuild: fix 'make modules' error when CONFIG_DEBUG_INFO_BTF_MODULES=y	2023-02-01 08:34:08 +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.