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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
..
accessibility
acpi * fix one ensures that a variable passed in by reference to 2018-07-13 10:54:01 -07:00
amba Merge branch 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm 2018-06-06 13:49:25 -07:00
android treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
ata ata: Remove depends on HAS_DMA in case of platform dependency 2018-07-02 13:18:22 -07:00
atm atm: zatm: Fix potential Spectre v1 2018-06-30 21:24:18 +09:00
auxdisplay treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
base PM / Domains: Don't power on at attach for the multi PM domain case 2018-07-03 16:42:51 +02:00
bcma dma-mapping updates for 4.18: 2018-06-04 10:58:12 -07:00
block for-linus-20180706 2018-07-06 19:13:42 -07:00
bluetooth bluetooth: hci_nokia: Don't include linux/unaligned/le_struct.h directly. 2018-06-17 08:38:55 +09:00
bus bus: ti-sysc: Use 2-factor allocator arguments 2018-07-02 04:24:44 -07:00
cdrom treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
char A couple of small fixes, one to the BMC side of things that fixes 2018-07-07 17:15:38 -07:00
clk clk: davinci: fixes for 4.18 2018-06-27 11:01:29 -07:00
clocksource clocksource: arm_arch_timer: Set arch_mem_timer cpumask to cpu_possible_mask 2018-07-10 22:12:47 +02:00
connector Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-06-06 18:39:49 -07:00
cpufreq cpufreq: Fix a circular lock dependency problem 2018-07-26 10:37:36 +02:00
cpuidle powerpc updates for 4.18 2018-06-07 10:23:33 -07:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2018-06-24 06:31:54 +08:00
dax * fix one ensures that a variable passed in by reference to 2018-07-13 10:54:01 -07:00
dca
devfreq treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
dio
dma dmaengine: k3dma: Off by one in k3_of_dma_simple_xlate() 2018-06-28 11:57:21 +05:30
dma-buf
edac treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
eisa
extcon treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
firewire treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
firmware efi/libstub/tpm: Initialize efi_physical_addr_t vars to zero for mixed mode 2018-06-22 10:58:27 +02:00
fmc treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
fpga fpga: altera-cvp: Fix an error handling path in 'altera_cvp_probe()' 2018-07-07 16:55:22 +02:00
fsi
gpio treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
gpu Merge branch 'etnaviv/fixes' of https://git.pengutronix.de/git/lst/linux into drm-fixes 2018-07-10 10:45:14 +10:00
hid Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid 2018-07-09 17:16:11 -07:00
hsi
hv treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
hwmon hwmon: (nct6775) Fix loop limit 2018-06-16 16:40:36 -07:00
hwspinlock hwspinlock updates for v4.18 2018-06-11 12:09:19 -07:00
hwtracing treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
i2c Merge branch 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2018-07-13 15:34:29 -07:00
ide treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
idle
iio iio: imu: inv_mpu6050: Fix probe() failure on older ACPI based machines 2018-06-24 14:50:52 +01:00
infiniband Regression, user visible bugs, and crashing fixes: 2018-07-13 12:42:14 -07:00
input Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2018-06-27 09:16:53 -07:00
iommu Revert "iommu/intel-iommu: Enable CONFIG_DMA_DIRECT_OPS=y and clean up intel_{alloc,free}_coherent()" 2018-07-05 13:32:06 -06:00
ipack treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
irqchip irqchip/gic-v3-its: Fix reprogramming of redistributors on CPU hotplug 2018-06-22 14:22:02 +02:00
isdn Revert changes to convert to ->poll_mask() and aio IOCB_CMD_POLL 2018-06-28 10:40:47 -07:00
leds treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
lightnvm for-linus-20180623 2018-06-24 06:33:54 +08:00
macintosh powerpc updates for 4.18 2018-06-07 10:23:33 -07:00
mailbox treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
mcb
md Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/shli/md 2018-07-02 12:40:59 -07:00
media bpf: fix attach type BPF_LIRC_MODE2 dependency wrt CONFIG_CGROUP_BPF 2018-06-26 11:28:38 +02:00
memory - Error path bug fix for overflow tests (Dan) 2018-06-12 18:28:00 -07:00
memstick treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
message treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
mfd Merge branch 'i2c/for-4.18' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2018-06-14 16:21:46 +09:00
misc ibmasm: don't write out of bounds in read handler 2018-07-07 09:59:35 +02:00
mmc mmc: sdhci-esdhc-imx: allow 1.8V modes without 100/200MHz pinctrl states 2018-07-09 11:17:47 +02:00
mtd mtd: spi-nor: cadence-quadspi: Fix direct mode write timeouts 2018-07-03 10:01:44 +02:00
mux
net pci-v4.18-fixes-2 2018-07-08 10:55:21 -07:00
nfc NFC: pn533: Fix wrong GFP flag usage 2018-06-25 21:36:45 +08:00
ntb - Error path bug fix for overflow tests (Dan) 2018-06-12 18:28:00 -07:00
nubus Char/Misc driver patches for 4.18-rc1 2018-06-05 16:20:22 -07:00
nvdimm * fix one ensures that a variable passed in by reference to 2018-07-13 10:54:01 -07:00
nvme nvme-rdma: fix possible double free of controller async event buffer 2018-06-28 16:29:54 +02:00
nvmem nvmem: Don't let a NULL cell_id for nvmem_cell_get() crash us 2018-07-07 17:30:25 +02:00
of - Error path bug fix for overflow tests (Dan) 2018-06-12 18:28:00 -07:00
opp PM / OPP: Update voltage in case freq == old_freq 2018-06-19 15:53:32 +05:30
oprofile treewide: Use array_size() in vmalloc() 2018-06-12 16:19:22 -07:00
parisc dma-mapping updates for 4.18: 2018-06-04 10:58:12 -07:00
parport docs: Fix some broken references 2018-06-15 18:10:01 -03:00
pci pci-v4.18-fixes-2 2018-07-08 10:55:21 -07:00
pcmcia treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
perf drivers/perf: xgene_pmu: Fix IOB SLOW PMU parser error 2018-06-18 17:48:42 +01:00
phy Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-06-06 18:39:49 -07:00
pinctrl pinctrl: mt7622: fix a kernel panic when pio don't work as EINT controller 2018-06-18 07:55:57 +02:00
platform fix a series of Documentation/ broken file name references 2018-06-15 18:10:01 -03:00
pnp media updates for v4.18-rc1 2018-06-07 12:34:37 -07:00
power treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
powercap treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
pps
ps3
ptp ptp: replace getnstimeofday64() with ktime_get_real_ts64() 2018-06-20 07:59:53 +09:00
pwm pwm: Changes for v4.18-rc1 2018-06-14 16:25:43 +09:00
rapidio treewide: Use array_size() in vmalloc() 2018-06-12 16:19:22 -07:00
ras
regulator treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
remoteproc treewide: use PHYS_ADDR_MAX to avoid type casting ULLONG_MAX 2018-06-15 07:55:25 +09:00
reset - Error path bug fix for overflow tests (Dan) 2018-06-12 18:28:00 -07:00
rpmsg rpmsg: smd: do not use mananged resources for endpoints and channels 2018-06-04 12:35:03 -07:00
rtc rtc: fix alarm read and set offset 2018-07-13 10:37:54 +02:00
s390 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2018-07-06 09:14:34 -07:00
sbus fix a series of Documentation/ broken file name references 2018-06-15 18:10:01 -03:00
scsi SCSI fixes on 20180706 2018-07-06 19:45:47 -07:00
sfi
sh treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
siox
slimbus treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
sn
soc Qualcomm Fixes for v4.18-rc2 2018-06-26 10:42:31 -07:00
soundwire docs: Fix more broken references 2018-06-15 18:11:26 -03:00
spi treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
spmi
ssb
staging staging: r8822be: Fix RTL8822be can't find any wireless AP 2018-07-06 17:44:35 +02:00
target scsi: target: Fix truncated PR-in ReadKeys response 2018-06-19 21:36:37 -04:00
tc
tee
thermal cpufreq: imx6q/thermal: imx: register cooling device depending on OF 2018-07-02 11:26:36 +02:00
thunderbolt thunderbolt: Notify userspace when boot_acl is changed 2018-07-07 17:29:17 +02:00
tty vt: prevent leaking uninitialized data to userspace via /dev/vcs* 2018-06-28 21:34:39 +09:00
uio uio: fix crash after the device is unregistered 2018-07-07 16:57:35 +02:00
usb USB: yurex: fix out-of-bounds uaccess in read handler 2018-07-06 17:21:34 +02:00
uwb treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
vfio vfio: Use get_user_pages_longterm correctly 2018-06-30 13:58:09 -06:00
vhost vhost_net: validate sock before trying to put its fd 2018-06-23 10:23:49 +09:00
video Solve a series of broken links for files under Documentation: 2018-06-17 05:25:18 +09:00
virt treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
virtio virtio, vhost: features, fixes 2018-06-16 06:35:02 +09:00
visorbus
vlynq
vme
w1 Char/Misc driver patches for 4.18-rc1 2018-06-05 16:20:22 -07:00
watchdog MIPS changes for 4.18 2018-06-12 12:56:02 -07:00
xen xen: fixes for 4.18-rc2 2018-06-23 20:44:11 +08:00
zorro - Introduce arithmetic overflow test helper functions (Rasmus) 2018-06-06 17:27:14 -07:00
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