Messages in this thread | | | From | Waiman Long <> | Subject | [PATCH v2 0/2] cpufreq: Fix a circular lock dependency problem | Date | Tue, 24 Jul 2018 14:26:03 -0400 |
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v2: - Remove the retry loop in the store method.
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 | 7 ++++++- include/linux/cpu.h | 2 ++ kernel/cpu.c | 6 ++++++ 3 files changed, 14 insertions(+), 1 deletion(-)
-- 1.8.3.1
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