On Thursday, October 29, 2015 08:08:38 AM Viresh Kumar wrote:
gov_queue_work() acquires cpufreq_governor_lock to allow cpufreq_governor_stop() to drain delayed work items possibly scheduled on CPUs that share the policy with a CPU being taken offline.
However, the same goal may be achieved in a more straightforward way if the policy pointer in the struct cpu_dbs_info matching the policy CPU is reset upfront by cpufreq_governor_stop() under the timer_mutex belonging to it and checked against NULL, under the same lock, at the beginning of dbs_timer().
In that case every instance of dbs_timer() run for a struct cpu_dbs_info sharing the policy pointer in question after cpufreq_governor_stop() has started will notice that that pointer is NULL and bail out immediately without queuing up any new work items. In turn, gov_cancel_work() called by cpufreq_governor_stop() before destroying timer_mutex will wait for all of the delayed work items currently running on the CPUs sharing the policy to drop the mutex, so it may be destroyed safely.
Make cpufreq_governor_stop() and dbs_timer() work as described and modify gov_queue_work() so it does not acquire cpufreq_governor_lock any more.
Signed-off-by: Viresh Kumar viresh.kumar@linaro.org
Applied, thanks!
Rafael