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48b60d6366
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Chen-Yu Tsai 48b60d6366 regulator: vctrl: Avoid lockdep warning in enable/disable ops 
[ Upstream commit 21e39809fd7c4b8ff3662f23e0168e87594c8ca8 ]

vctrl_enable() and vctrl_disable() call regulator_enable() and
regulator_disable(), respectively. However, vctrl_* are regulator ops
and should not be calling the locked regulator APIs. Doing so results in
a lockdep warning.

Instead of exporting more internal regulator ops, model the ctrl supply
as an actual supply to vctrl-regulator. At probe time this driver still
needs to use the consumer API to fetch its constraints, but otherwise
lets the regulator core handle the upstream supply for it.

The enable/disable/is_enabled ops are not removed, but now only track
state internally. This preserves the original behavior with the ops
being available, but one could argue that the original behavior was
already incorrect: the internal state would not match the upstream
supply if that supply had another consumer that enabled the supply,
while vctrl-regulator was not enabled.

The lockdep warning is as follows:

	WARNING: possible circular locking dependency detected
	5.14.0-rc6 #2 Not tainted
	------------------------------------------------------
	swapper/0/1 is trying to acquire lock:
	ffffffc011306d00 (regulator_list_mutex){+.+.}-{3:3}, at:
		regulator_lock_dependent (arch/arm64/include/asm/current.h:19
					  include/linux/ww_mutex.h:111
					  drivers/regulator/core.c:329)

	but task is already holding lock:
	ffffff8004a77160 (regulator_ww_class_mutex){+.+.}-{3:3}, at:
		regulator_lock_recursive (drivers/regulator/core.c:156
					  drivers/regulator/core.c:263)

	which lock already depends on the new lock.

	the existing dependency chain (in reverse order) is:

	-> #2 (regulator_ww_class_mutex){+.+.}-{3:3}:
	__mutex_lock_common (include/asm-generic/atomic-instrumented.h:606
			     include/asm-generic/atomic-long.h:29
			     kernel/locking/mutex.c:103
			     kernel/locking/mutex.c:144
			     kernel/locking/mutex.c:963)
	ww_mutex_lock (kernel/locking/mutex.c:1199)
	regulator_lock_recursive (drivers/regulator/core.c:156
				  drivers/regulator/core.c:263)
	regulator_lock_dependent (drivers/regulator/core.c:343)
	regulator_enable (drivers/regulator/core.c:2808)
	set_machine_constraints (drivers/regulator/core.c:1536)
	regulator_register (drivers/regulator/core.c:5486)
	devm_regulator_register (drivers/regulator/devres.c:196)
	reg_fixed_voltage_probe (drivers/regulator/fixed.c:289)
	platform_probe (drivers/base/platform.c:1427)
	[...]

	-> #1 (regulator_ww_class_acquire){+.+.}-{0:0}:
	regulator_lock_dependent (include/linux/ww_mutex.h:129
				  drivers/regulator/core.c:329)
	regulator_enable (drivers/regulator/core.c:2808)
	set_machine_constraints (drivers/regulator/core.c:1536)
	regulator_register (drivers/regulator/core.c:5486)
	devm_regulator_register (drivers/regulator/devres.c:196)
	reg_fixed_voltage_probe (drivers/regulator/fixed.c:289)
	[...]

	-> #0 (regulator_list_mutex){+.+.}-{3:3}:
	__lock_acquire (kernel/locking/lockdep.c:3052 (discriminator 4)
			kernel/locking/lockdep.c:3174 (discriminator 4)
			kernel/locking/lockdep.c:3789 (discriminator 4)
			kernel/locking/lockdep.c:5015 (discriminator 4))
	lock_acquire (arch/arm64/include/asm/percpu.h:39
		      kernel/locking/lockdep.c:438
		      kernel/locking/lockdep.c:5627)
	__mutex_lock_common (include/asm-generic/atomic-instrumented.h:606
			     include/asm-generic/atomic-long.h:29
			     kernel/locking/mutex.c:103
			     kernel/locking/mutex.c:144
			     kernel/locking/mutex.c:963)
	mutex_lock_nested (kernel/locking/mutex.c:1125)
	regulator_lock_dependent (arch/arm64/include/asm/current.h:19
				  include/linux/ww_mutex.h:111
				  drivers/regulator/core.c:329)
	regulator_enable (drivers/regulator/core.c:2808)
	vctrl_enable (drivers/regulator/vctrl-regulator.c:400)
	_regulator_do_enable (drivers/regulator/core.c:2617)
	_regulator_enable (drivers/regulator/core.c:2764)
	regulator_enable (drivers/regulator/core.c:308
			  drivers/regulator/core.c:2809)
	_set_opp (drivers/opp/core.c:819 drivers/opp/core.c:1072)
	dev_pm_opp_set_rate (drivers/opp/core.c:1164)
	set_target (drivers/cpufreq/cpufreq-dt.c:62)
	__cpufreq_driver_target (drivers/cpufreq/cpufreq.c:2216
				 drivers/cpufreq/cpufreq.c:2271)
	cpufreq_online (drivers/cpufreq/cpufreq.c:1488 (discriminator 2))
	cpufreq_add_dev (drivers/cpufreq/cpufreq.c:1563)
	subsys_interface_register (drivers/base/bus.c:?)
	cpufreq_register_driver (drivers/cpufreq/cpufreq.c:2819)
	dt_cpufreq_probe (drivers/cpufreq/cpufreq-dt.c:344)
	[...]

	other info that might help us debug this:

	Chain exists of:
	  regulator_list_mutex --> regulator_ww_class_acquire --> regulator_ww_class_mutex

	 Possible unsafe locking scenario:

	       CPU0                    CPU1
	       ----                    ----
	  lock(regulator_ww_class_mutex);
				       lock(regulator_ww_class_acquire);
				       lock(regulator_ww_class_mutex);
	  lock(regulator_list_mutex);

	 *** DEADLOCK ***

	6 locks held by swapper/0/1:
	#0: ffffff8002d32188 (&dev->mutex){....}-{3:3}, at:
		__device_driver_lock (drivers/base/dd.c:1030)
	#1: ffffffc0111a0520 (cpu_hotplug_lock){++++}-{0:0}, at:
		cpufreq_register_driver (drivers/cpufreq/cpufreq.c:2792 (discriminator 2))
	#2: ffffff8002a8d918 (subsys mutex#9){+.+.}-{3:3}, at:
		subsys_interface_register (drivers/base/bus.c:1033)
	#3: ffffff800341bb90 (&policy->rwsem){+.+.}-{3:3}, at:
		cpufreq_online (include/linux/bitmap.h:285
				include/linux/cpumask.h:405
				drivers/cpufreq/cpufreq.c:1399)
	#4: ffffffc011f0b7b8 (regulator_ww_class_acquire){+.+.}-{0:0}, at:
		regulator_enable (drivers/regulator/core.c:2808)
	#5: ffffff8004a77160 (regulator_ww_class_mutex){+.+.}-{3:3}, at:
		regulator_lock_recursive (drivers/regulator/core.c:156
		drivers/regulator/core.c:263)

	stack backtrace:
	CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.14.0-rc6 #2 7c8f8996d021ed0f65271e6aeebf7999de74a9fa
	Hardware name: Google Scarlet (DT)
	Call trace:
	dump_backtrace (arch/arm64/kernel/stacktrace.c:161)
	show_stack (arch/arm64/kernel/stacktrace.c:218)
	dump_stack_lvl (lib/dump_stack.c:106 (discriminator 2))
	dump_stack (lib/dump_stack.c:113)
	print_circular_bug (kernel/locking/lockdep.c:?)
	check_noncircular (kernel/locking/lockdep.c:?)
	__lock_acquire (kernel/locking/lockdep.c:3052 (discriminator 4)
			kernel/locking/lockdep.c:3174 (discriminator 4)
			kernel/locking/lockdep.c:3789 (discriminator 4)
			kernel/locking/lockdep.c:5015 (discriminator 4))
	lock_acquire (arch/arm64/include/asm/percpu.h:39
		      kernel/locking/lockdep.c:438
		      kernel/locking/lockdep.c:5627)
	__mutex_lock_common (include/asm-generic/atomic-instrumented.h:606
			     include/asm-generic/atomic-long.h:29
			     kernel/locking/mutex.c:103
			     kernel/locking/mutex.c:144
			     kernel/locking/mutex.c:963)
	mutex_lock_nested (kernel/locking/mutex.c:1125)
	regulator_lock_dependent (arch/arm64/include/asm/current.h:19
				  include/linux/ww_mutex.h:111
				  drivers/regulator/core.c:329)
	regulator_enable (drivers/regulator/core.c:2808)
	vctrl_enable (drivers/regulator/vctrl-regulator.c:400)
	_regulator_do_enable (drivers/regulator/core.c:2617)
	_regulator_enable (drivers/regulator/core.c:2764)
	regulator_enable (drivers/regulator/core.c:308
			  drivers/regulator/core.c:2809)
	_set_opp (drivers/opp/core.c:819 drivers/opp/core.c:1072)
	dev_pm_opp_set_rate (drivers/opp/core.c:1164)
	set_target (drivers/cpufreq/cpufreq-dt.c:62)
	__cpufreq_driver_target (drivers/cpufreq/cpufreq.c:2216
				 drivers/cpufreq/cpufreq.c:2271)
	cpufreq_online (drivers/cpufreq/cpufreq.c:1488 (discriminator 2))
	cpufreq_add_dev (drivers/cpufreq/cpufreq.c:1563)
	subsys_interface_register (drivers/base/bus.c:?)
	cpufreq_register_driver (drivers/cpufreq/cpufreq.c:2819)
	dt_cpufreq_probe (drivers/cpufreq/cpufreq-dt.c:344)
	[...]

Reported-by: Brian Norris <briannorris@chromium.org>
Fixes: f8702f9e4a ("regulator: core: Use ww_mutex for regulators locking")
Fixes: e915331149 ("regulator: vctrl-regulator: Avoid deadlock getting and setting the voltage")
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20210825033704.3307263-3-wenst@chromium.org
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2024-07-05 19:10:30 +02:00
arch x86/mce: Defer processing of early errors 2024-07-05 19:10:21 +02:00
block blk-crypto: fix check for too-large dun_bytes 2024-07-05 19:10:30 +02:00
certs certs: Trigger creation of RSA module signing key if it's not an RSA key 2024-07-05 19:10:21 +02:00
crypto init: add dsm gpl source 2024-07-05 18:00:04 +02:00
Documentation dt-bindings: sifive-l2-cache: Fix 'select' matching 2024-07-05 19:00:49 +02:00
drivers regulator: vctrl: Avoid lockdep warning in enable/disable ops 2024-07-05 19:10:30 +02:00
fs udf_get_extendedattr() had no boundary checks. 2024-07-05 19:09:51 +02:00
include block: return ELEVATOR_DISCARD_MERGE if possible 2024-07-05 19:10:07 +02:00
init init: add dsm gpl source 2024-07-05 18:00:04 +02:00
ipc ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry 2021-05-26 12:06:54 +02:00
kernel genirq/timings: Fix error return code in irq_timings_test_irqs() 2024-07-05 19:10:07 +02:00
lib lib/mpi: use kcalloc in mpi_resize 2024-07-05 19:10:07 +02:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm mm/page_alloc: speed up the iteration of max_order 2024-07-05 19:06:11 +02:00
net netfilter: nftables: clone set element expression template 2024-07-05 19:07:11 +02:00
samples samples/bpf: Fix the error return code of xdp_redirect's main() 2021-07-14 16:56:23 +02:00
scripts scripts/tracing: fix the bug that can't parse raw_trace_func 2024-07-05 18:52:27 +02:00
security bpf: Add lockdown check for probe_write_user helper 2024-07-05 18:53:10 +02:00
sound ALSA: usb-audio: Add registration quirk for JBL Quantum 800 2024-07-05 19:07:18 +02:00
SynoBuildConf init: add dsm gpl source 2024-07-05 18:00:04 +02:00
synology init: add dsm gpl source 2024-07-05 18:00:04 +02:00
tools perf annotate: Fix jump parsing for C++ code. 2024-07-05 19:01:01 +02:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt KVM: Do not leak memory for duplicate debugfs directories 2024-07-05 18:52:31 +02:00
.clang-format init: add dsm gpl source 2024-07-05 18:00:04 +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 kbuild: generate Module.symvers only when vmlinux exists 2021-05-19 10:12:59 +02:00
.mailmap mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Jason Cooper to CREDITS 2020-11-30 10:20:34 +01:00
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 init: add dsm gpl source 2024-07-05 18:00:04 +02:00
Makefile init: add dsm gpl source 2024-07-05 18:00:04 +02:00
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.