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Subject[PATCH 0/2] cpufreq: Fix a circular lock dependency problem
This patchset works around a circular lock dependency issue in the
cpufreq driver reported by lockdep. The two locks involved are the
cpu_hotplup_lock and the reference count of a sysfs file.

The cpufreq_register_driver() function uses the lock sequence:

cpus_read_lock --> kn->count

Whereas the cpufreq sysfs store method uses the sequence:

kn->count --> cpus_read_lock

This is not really an issue as a shared lock is used on the
cpu_hotplup_lock. However, the lockdep code isn't able to handle
shared locking. So one way to work around this is to define a
cpus_read_trylock() function and uses it in the store method instead.

Waiman Long (2):
cpu/hotplug: Add a cpus_read_trylock() function
cpufreq: Fix a circular lock dependency problem

drivers/cpufreq/cpufreq.c | 16 +++++++++++++++-
include/linux/cpu.h | 2 ++
kernel/cpu.c | 6 ++++++
3 files changed, 23 insertions(+), 1 deletion(-)


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