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61bfbf7951
The field 'transition_task' of policy structure is used to track the
task which is performing the frequency transition. Using this field to
print a warning once detect a case where the same task is calling
_begin() again before completing the preivous frequency transition via
the _end().
However, there is a potential race condition in _end() and _begin() APIs
while updating the field 'transition_task' of policy, the scenario is
depicted below:
Task A Task B
/* 1st freq transition */
Invoke _begin() {
...
...
}
/* 2nd freq transition */
Invoke _begin() {
... //waiting for A to
... //clear
... //transition_ongoing
... //in _end() for
... //the 1st transition
|
Change the frequency |
|
Invoke _end() { |
... |
... |
transition_ongoing = false; V
transition_ongoing = true;
transition_task = current;
transition_task = NULL;
... //A overwrites the task
... //performing the transition
... //result in error warning.
}
To fix this race condition, the transition_lock of policy structure is
now acquired before updating policy structure in _end() API. Which ensure
that only one task can update the 'transition_task' field at a time.
Link: https://lore.kernel.org/all/b3c61d8a-d52d-3136-fbf0-d1de9f1ba411@huawei.com/
Fixes:
|
||
---|---|---|
.. | ||
acpi-cpufreq.c | ||
amd-pstate-trace.c | ||
amd-pstate-trace.h | ||
amd-pstate-ut.c | ||
amd-pstate.c | ||
amd_freq_sensitivity.c | ||
apple-soc-cpufreq.c | ||
armada-8k-cpufreq.c | ||
armada-37xx-cpufreq.c | ||
bmips-cpufreq.c | ||
brcmstb-avs-cpufreq.c | ||
cppc_cpufreq.c | ||
cpufreq-dt-platdev.c | ||
cpufreq-dt.c | ||
cpufreq-dt.h | ||
cpufreq-nforce2.c | ||
cpufreq.c | ||
cpufreq_conservative.c | ||
cpufreq_governor.c | ||
cpufreq_governor.h | ||
cpufreq_governor_attr_set.c | ||
cpufreq_ondemand.c | ||
cpufreq_ondemand.h | ||
cpufreq_performance.c | ||
cpufreq_powersave.c | ||
cpufreq_stats.c | ||
cpufreq_userspace.c | ||
davinci-cpufreq.c | ||
e_powersaver.c | ||
elanfreq.c | ||
freq_table.c | ||
gx-suspmod.c | ||
highbank-cpufreq.c | ||
ia64-acpi-cpufreq.c | ||
imx-cpufreq-dt.c | ||
imx6q-cpufreq.c | ||
intel_pstate.c | ||
Kconfig | ||
Kconfig.arm | ||
Kconfig.powerpc | ||
Kconfig.x86 | ||
kirkwood-cpufreq.c | ||
longhaul.c | ||
longhaul.h | ||
longrun.c | ||
loongson2_cpufreq.c | ||
Makefile | ||
maple-cpufreq.c | ||
mediatek-cpufreq-hw.c | ||
mediatek-cpufreq.c | ||
mvebu-cpufreq.c | ||
omap-cpufreq.c | ||
p4-clockmod.c | ||
pasemi-cpufreq.c | ||
pcc-cpufreq.c | ||
pmac32-cpufreq.c | ||
pmac64-cpufreq.c | ||
powernow-k6.c | ||
powernow-k7.c | ||
powernow-k7.h | ||
powernow-k8.c | ||
powernow-k8.h | ||
powernv-cpufreq.c | ||
ppc_cbe_cpufreq.c | ||
ppc_cbe_cpufreq.h | ||
ppc_cbe_cpufreq_pervasive.c | ||
ppc_cbe_cpufreq_pmi.c | ||
pxa2xx-cpufreq.c | ||
pxa3xx-cpufreq.c | ||
qcom-cpufreq-hw.c | ||
qcom-cpufreq-nvmem.c | ||
qoriq-cpufreq.c | ||
raspberrypi-cpufreq.c | ||
s3c64xx-cpufreq.c | ||
s5pv210-cpufreq.c | ||
sa1110-cpufreq.c | ||
sc520_freq.c | ||
scmi-cpufreq.c | ||
scpi-cpufreq.c | ||
sh-cpufreq.c | ||
sparc-us2e-cpufreq.c | ||
sparc-us3-cpufreq.c | ||
spear-cpufreq.c | ||
speedstep-centrino.c | ||
speedstep-ich.c | ||
speedstep-lib.c | ||
speedstep-lib.h | ||
speedstep-smi.c | ||
sti-cpufreq.c | ||
sun50i-cpufreq-nvmem.c | ||
tegra20-cpufreq.c | ||
tegra124-cpufreq.c | ||
tegra186-cpufreq.c | ||
tegra194-cpufreq.c | ||
ti-cpufreq.c | ||
vexpress-spc-cpufreq.c |