Revision - 999976e - cpufreq: use cpufreq_cpu_get() to avoid cpufreq_get() race conditions - origin: https://github.com/torvalds/linux

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17 August 2024, 15:42:30 UTC

Revision 999976e0f6233322a878b0b7148c810544d6c8a8 authored by Aaron Plattner on 04 March 2014, 20:42:15 UTC, committed by Rafael J. Wysocki on 06 March 2014, 12:25:16 UTC

cpufreq: use cpufreq_cpu_get() to avoid cpufreq_get() race conditions

If a module calls cpufreq_get while cpufreq is initializing, it's
possible for it to be called after cpufreq_driver is set but before
cpufreq_cpu_data is written during subsys_interface_register.  This
happens because cpufreq_get doesn't take the cpufreq_driver_lock
around its use of cpufreq_cpu_data.

Fix this by using cpufreq_cpu_get(cpu) to look up the policy rather
than reading it out of cpufreq_cpu_data directly.  cpufreq_cpu_get()
takes the appropriate locks to prevent this race from happening.

Since it's possible for policy to be NULL if the caller passes in an
invalid CPU number or calls the function before cpufreq is initialized,
delete the BUG_ON(!policy) and simply return 0.  Don't try to return
-ENOENT because that's negative and the function returns an unsigned
integer.

References: https://bbs.archlinux.org/viewtopic.php?id=177934
Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
Cc: 3.13+ <stable@vger.kernel.org> # 3.13+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 parent 0414855

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Tip revision: 999976e0f6233322a878b0b7148c810544d6c8a8 authored by Aaron Plattner on 04 March 2014, 20:42:15 UTC
cpufreq: use cpufreq_cpu_get() to avoid cpufreq_get() race conditions

Tip revision: 999976e

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cpufreq: use cpufreq_cpu_get() to avoid cpufreq_get() race conditions

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