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9b3d9bb3e4
linux/drivers/cpufreq
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Waiman Long 9b3d9bb3e4 cpufreq: Fix a circular lock dependency problem 
With lockdep turned on, the following circular lock dependency problem
was reported:

[   57.470040] ======================================================
[   57.502900] WARNING: possible circular locking dependency detected
[   57.535208] 4.18.0-0.rc3.1.el8+7.x86_64+debug #1 Tainted: G
[   57.577761] ------------------------------------------------------
[   57.609714] tuned/1505 is trying to acquire lock:
[   57.633808] 00000000559deec5 (cpu_hotplug_lock.rw_sem){++++}, at: store+0x27/0x120
[   57.672880]
[   57.672880] but task is already holding lock:
[   57.702184] 000000002136ca64 (kn->count#118){++++}, at: kernfs_fop_write+0x1d0/0x410
[   57.742176]
[   57.742176] which lock already depends on the new lock.
[   57.742176]
[   57.785220]
[   57.785220] the existing dependency chain (in reverse order) is:
    :
[   58.932512] other info that might help us debug this:
[   58.932512]
[   58.973344] Chain exists of:
[   58.973344]   cpu_hotplug_lock.rw_sem --> subsys mutex#5 --> kn->count#118
[   58.973344]
[   59.030795]  Possible unsafe locking scenario:
[   59.030795]
[   59.061248]        CPU0                    CPU1
[   59.085377]        ----                    ----
[   59.108160]   lock(kn->count#118);
[   59.124935]                                lock(subsys mutex#5);
[   59.156330]                                lock(kn->count#118);
[   59.186088]   lock(cpu_hotplug_lock.rw_sem);
[   59.208541]
[   59.208541]  *** DEADLOCK ***

In the cpufreq_register_driver() function, the lock sequence is:

  cpus_read_lock --> kn->count

For the cpufreq sysfs store method, the lock sequence is:

  kn->count --> cpus_read_lock

These sequences are actually safe as they are taking a share lock on
cpu_hotplug_lock. However, the current lockdep code doesn't check for
share locking when detecting circular lock dependency.  Fixing that
could be a substantial effort.

Instead, we can work around this problem by using cpus_read_trylock()
in the store method which is much simpler. The chance of not getting
the read lock is very small. If that happens, the userspace application
that writes the sysfs file will get an error.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2018-07-26 10:37:36 +02:00
..
acpi-cpufreq.c Additional power management updates for 4.18-rc1 2018-06-13 07:24:18 -07:00
amd_freq_sensitivity.c cpufreq: AMD: Ignore the check for ProcFeedback in ST/CZ 2018-02-07 11:26:37 +01:00
arm_big_little_dt.c cpufreq: arm_big_little: make cpufreq_arm_bL_ops structures const 2017-11-08 23:22:20 +01:00
arm_big_little.c treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
arm_big_little.h cpufreq: arm_big_little: make function arguments and structure pointer const 2017-11-08 23:22:19 +01:00
armada-37xx-cpufreq.c cpufreq: armada-37xx: Add AVS support 2018-07-18 10:10:25 +02:00
bmips-cpufreq.c treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
brcmstb-avs-cpufreq.c treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
cppc_cpufreq.c cpufreq / CPPC: Add cpuinfo_cur_freq support for CPPC 2018-07-18 10:13:16 +02:00
cpufreq_conservative.c cpufreq: governor: Drop min_sampling_rate 2017-07-22 02:25:20 +02:00
cpufreq_governor_attr_set.c cpufreq: governor: Move abstract gov_attr_set code to seperate file 2016-04-02 01:09:01 +02:00
cpufreq_governor.c cpufreq: governors: Fix long idle detection logic in load calculation 2018-06-08 11:40:44 +02:00
cpufreq_governor.h cpufreq: Replace "max_transition_latency" with "dynamic_switching" 2017-07-26 00:15:45 +02:00
cpufreq_ondemand.c cpufreq: governor: Drop min_sampling_rate 2017-07-22 02:25:20 +02:00
cpufreq_ondemand.h cpufreq: ondemand: Don't keep a copy of freq_table pointer 2016-06-09 00:58:06 +02:00
cpufreq_performance.c cpufreq: governor: Get rid of governor events 2016-06-02 23:24:15 +02:00
cpufreq_powersave.c cpufreq: governor: Get rid of governor events 2016-06-02 23:24:15 +02:00
cpufreq_stats.c cpufreq: stats: Change return type of cpufreq_stats_update() as void 2018-01-05 13:22:46 +01:00
cpufreq_userspace.c cpufreq: governor: Get rid of governor events 2016-06-02 23:24:15 +02:00
cpufreq-dt-platdev.c cpufreq: Add Kryo CPU scaling driver 2018-05-30 12:53:11 +02:00
cpufreq-dt.c cpufreq: dt: Allow platform specific suspend/resume callbacks 2018-05-10 11:43:59 +02:00
cpufreq-dt.h cpufreq: dt: Allow platform specific suspend/resume callbacks 2018-05-10 11:43:59 +02:00
cpufreq-nforce2.c cpufreq: Add CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING cpufreq driver flag 2017-07-26 00:15:46 +02:00
cpufreq.c cpufreq: Fix a circular lock dependency problem 2018-07-26 10:37:36 +02:00
davinci-cpufreq.c ARM: davinci: da850: fix da850_set_pll0rate() 2017-01-02 15:02:51 +05:30
e_powersaver.c cpufreq: e_powersaver: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
elanfreq.c cpufreq: elanfreq: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
exynos5440-cpufreq.c cpufreq: Add and use cpufreq_for_each_{valid_,}entry_idx() 2018-02-08 10:21:39 +01:00
freq_table.c cpufreq: Drop cpufreq_table_validate_and_show() 2018-04-10 08:40:45 +02:00
gx-suspmod.c cpufreq: Add CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING cpufreq driver flag 2017-07-26 00:15:46 +02:00
highbank-cpufreq.c Merge branch 'mailbox-for-linus' of git://git.linaro.org/landing-teams/working/fujitsu/integration 2014-10-21 11:21:19 -07:00
ia64-acpi-cpufreq.c treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
imx6q-cpufreq.c cpufreq: imx6q/thermal: imx: register cooling device depending on OF 2018-07-02 11:26:36 +02:00
intel_pstate.c Merge back cpufreq material for 4.19. 2018-07-25 13:28:01 +02:00
Kconfig cpufreq: remove at32ap-cpufreq 2018-02-07 11:44:23 +01:00
Kconfig.arm cpufreq: kryo: allow building as a loadable module 2018-06-06 08:29:29 +02:00
Kconfig.powerpc cpufreq: qoriq: rename the driver 2015-03-18 22:35:16 +01:00
Kconfig.x86 sched/x86: Change CONFIG_SCHED_ITMT to CONFIG_SCHED_MC_PRIO 2016-11-30 08:27:08 +01:00
kirkwood-cpufreq.c cpufreq: kirkwood-cpufreq:- Handle return value of clk_prepare_enable() 2017-05-30 00:09:41 +02:00
longhaul.c treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
longhaul.h
longrun.c cpufreq: Don't set transition_latency for setpolicy drivers 2017-07-26 00:15:43 +02:00
loongson1-cpufreq.c CPUFREQ: Loongson1: Replace goto out with return in ls1x_cpufreq_probe() 2016-05-13 14:02:08 +02:00
loongson2_cpufreq.c cpufreq: Loongson2: constify platform_device_id 2017-08-18 01:44:21 +02:00
Makefile cpufreq: Add Kryo CPU scaling driver 2018-05-30 12:53:11 +02:00
maple-cpufreq.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
mediatek-cpufreq.c cpufreq: mediatek: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
mvebu-cpufreq.c cpufreq: mvebu: Free opp if registering failed 2017-12-16 02:29:43 +01:00
omap-cpufreq.c PM / OPP: Update OPP users to put reference 2017-01-30 09:22:21 +01:00
p4-clockmod.c cpufreq: p4-clockmod: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
pasemi-cpufreq.c cpufreq: Add and use cpufreq_for_each_{valid_,}entry_idx() 2018-02-08 10:21:39 +01:00
pcc-cpufreq.c Merge back cpufreq material for 4.19. 2018-07-25 13:28:01 +02:00
pmac32-cpufreq.c cpufreq: Add CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING cpufreq driver flag 2017-07-26 00:15:46 +02:00
pmac64-cpufreq.c cpufreq: Convert to using %pOF instead of full_name 2017-08-25 01:20:46 +02:00
powernow-k6.c cpufreq: powernow: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
powernow-k7.c cpufreq: powernow: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
powernow-k7.h
powernow-k8.c cpufreq: powernow: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
powernow-k8.h
powernv-cpufreq.c cpufreq: powernv: Fix hardlockup due to synchronous smp_call in timer interrupt 2018-04-27 16:16:10 +10:00
ppc_cbe_cpufreq_pervasive.c
ppc_cbe_cpufreq_pmi.c cpufreq: Remove CPUFREQ_START notifier event 2017-02-04 00:05:30 +01:00
ppc_cbe_cpufreq.c cpufreq: ppc_cbe: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
ppc_cbe_cpufreq.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
pxa2xx-cpufreq.c cpufreq: pxa: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
pxa3xx-cpufreq.c treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
qcom-cpufreq-kryo.c cpufreq: qcom-kryo: Silently error out on EPROBE_DEFER 2018-07-18 10:14:38 +02:00
qoriq-cpufreq.c cpufreq: qoirq: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
s3c24xx-cpufreq-debugfs.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
s3c24xx-cpufreq.c treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
s3c64xx-cpufreq.c cpufreq: s3c64xx: remove incorrect __init annotation 2016-12-21 02:54:18 +01:00
s3c2410-cpufreq.c cpufreq: s3c24xx: Remove some dead code 2014-07-19 04:24:59 +09:00
s3c2412-cpufreq.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
s3c2416-cpufreq.c cpufreq: s3c2416: double free on driver init error path 2017-02-09 01:22:45 +01:00
s3c2440-cpufreq.c cpufreq: s3c2440: fix spelling mistake: "divsiors" -> "divisors" 2018-05-10 11:50:42 +02:00
s5pv210-cpufreq.c cpufreq: s5pv210: add missing of_node_put() 2017-07-26 22:54:01 +02:00
sa1100-cpufreq.c cpufreq: Add CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING cpufreq driver flag 2017-07-26 00:15:46 +02:00
sa1110-cpufreq.c cpufreq: Add CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING cpufreq driver flag 2017-07-26 00:15:46 +02:00
sc520_freq.c cpufreq: sc520: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
scmi-cpufreq.c firmware: arm_scmi: rename get_transition_latency and add_opps_to_device 2018-05-10 10:49:40 +01:00
scpi-cpufreq.c cpufreq: scpi: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
sfi-cpufreq.c treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
sh-cpufreq.c cpufreq: sh: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
sparc-us2e-cpufreq.c cpufreq: sparc: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
sparc-us3-cpufreq.c cpufreq: sparc: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
spear-cpufreq.c treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
speedstep-centrino.c cpufreq: speedstep: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
speedstep-ich.c cpufreq: speedstep: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
speedstep-lib.c cpufreq: speedstep: fix speedstep_detect_processor()'s return type 2018-05-10 11:46:00 +02:00
speedstep-lib.h
speedstep-smi.c cpufreq: speedstep: Don't validate the frequency table twice 2018-03-20 12:07:52 +01:00
sti-cpufreq.c cpufreq: Convert to using %pOF instead of full_name 2017-08-25 01:20:46 +02:00
tango-cpufreq.c cpufreq: dt: Don't use generic platdev driver for tango 2017-07-22 02:20:59 +02:00
tegra20-cpufreq.c cpufreq: tegra20: Wrap cpufreq into platform driver 2018-05-21 13:44:24 +02:00
tegra124-cpufreq.c cpufreq: tegra124: No need of setting platform-data 2016-04-09 01:12:09 +02:00
tegra186-cpufreq.c cpufreq: tegra186: Don't validate the frequency table twice 2018-03-20 12:07:53 +01:00
ti-cpufreq.c cpufreq: ti-cpufreq: Use devres managed API in probe() 2018-06-06 08:34:31 +02:00
unicore2-cpufreq.c cpufreq: Add CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING cpufreq driver flag 2017-07-26 00:15:46 +02:00
vexpress-spc-cpufreq.c cpufreq: arm_big_little: make cpufreq_arm_bL_ops structures const 2017-11-08 23:22:20 +01:00