From: Rafael J. Wysocki rafael.j.wysocki@intel.com
Use the observation that if skip_work in struct cpu_common_dbs_info is an atomic_t variable, the code may be rearranged to avoid using the timer_lock spinlock in which case that lock is not necessary any more.
Make that change and drop timer_lock.
Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com ---
This is on top of my current linux-next branch. Completely experimental and untested.
--- drivers/cpufreq/cpufreq_governor.c | 29 +++++++---------------------- drivers/cpufreq/cpufreq_governor.h | 9 ++------- 2 files changed, 9 insertions(+), 29 deletions(-)
Index: linux-pm/drivers/cpufreq/cpufreq_governor.c =================================================================== --- linux-pm.orig/drivers/cpufreq/cpufreq_governor.c +++ linux-pm/drivers/cpufreq/cpufreq_governor.c @@ -186,22 +186,15 @@ static inline void gov_cancel_timers(str
void gov_cancel_work(struct cpu_common_dbs_info *shared) { - unsigned long flags; - /* * No work will be queued from timer handlers after skip_work is * updated. And so we can safely cancel the work first and then the * timers. */ - spin_lock_irqsave(&shared->timer_lock, flags); - shared->skip_work++; - spin_unlock_irqrestore(&shared->timer_lock, flags); - + atomic_inc(&shared->skip_work); cancel_work_sync(&shared->work); - gov_cancel_timers(shared->policy); - - shared->skip_work = 0; + atomic_set(&shared->skip_work, 0); }
/* Will return if we need to evaluate cpu load again or not */ @@ -229,7 +222,6 @@ static void dbs_work_handler(struct work struct cpufreq_policy *policy; struct dbs_data *dbs_data; unsigned int sampling_rate, delay; - unsigned long flags; bool eval_load;
policy = shared->policy; @@ -258,9 +250,7 @@ static void dbs_work_handler(struct work delay = dbs_data->cdata->gov_dbs_timer(policy, eval_load); mutex_unlock(&shared->timer_mutex);
- spin_lock_irqsave(&shared->timer_lock, flags); - shared->skip_work--; - spin_unlock_irqrestore(&shared->timer_lock, flags); + atomic_dec(&shared->skip_work);
gov_add_timers(policy, delay); } @@ -269,9 +259,6 @@ static void dbs_timer_handler(unsigned l { struct cpu_dbs_info *cdbs = (struct cpu_dbs_info *)data; struct cpu_common_dbs_info *shared = cdbs->shared; - unsigned long flags; - - spin_lock_irqsave(&shared->timer_lock, flags);
/* * Timer handler isn't allowed to queue work at the moment, because: @@ -279,12 +266,10 @@ static void dbs_timer_handler(unsigned l * - We are stopping the governor * - Or we are updating the sampling rate of ondemand governor */ - if (!shared->skip_work) { - shared->skip_work++; + if (atomic_inc_return(&shared->skip_work) > 1) + atomic_dec(&shared->skip_work); + else queue_work(system_wq, &shared->work); - } - - spin_unlock_irqrestore(&shared->timer_lock, flags); }
static void set_sampling_rate(struct dbs_data *dbs_data, @@ -315,7 +300,7 @@ static int alloc_common_dbs_info(struct cdata->get_cpu_cdbs(j)->shared = shared;
mutex_init(&shared->timer_mutex); - spin_lock_init(&shared->timer_lock); + atomic_set(&shared->skip_work, 0); INIT_WORK(&shared->work, dbs_work_handler); return 0; } Index: linux-pm/drivers/cpufreq/cpufreq_governor.h =================================================================== --- linux-pm.orig/drivers/cpufreq/cpufreq_governor.h +++ linux-pm/drivers/cpufreq/cpufreq_governor.h @@ -17,6 +17,7 @@ #ifndef _CPUFREQ_GOVERNOR_H #define _CPUFREQ_GOVERNOR_H
+#include <linux/atomic.h> #include <linux/cpufreq.h> #include <linux/kernel_stat.h> #include <linux/module.h> @@ -137,14 +138,8 @@ struct cpu_common_dbs_info { */ struct mutex timer_mutex;
- /* - * Per policy lock that serializes access to queuing work from timer - * handlers. - */ - spinlock_t timer_lock; - ktime_t time_stamp; - unsigned int skip_work; + atomic_t skip_work; struct work_struct work; };