On 04-12-15, 02:18, Rafael J. Wysocki wrote:
- shared->skip_work--;
Is there any reason for incrementing and decrementing this instead of setting it to either 0 or 1 (or maybe either 'true' or 'false' for that matter)?
If my reading of the patch is correct, it can only be either 0 or 1 anyway, right?
No. It can be 0, 1 or 2.
If the timer handler is running on any CPU, we increment skip_work, so its value is 1. If at the same time, we try to stop the governor, we increment it again and its value is 2 now.
Once timer-handler finishes, it decrements it and its value become 1. Which guarantees that no other timer handler starts executing at this point of time and we can safely do gov_cancel_timers(). And once we are sure that we don't have any work/timer left, we make it 0 (as we aren't sure of the current value, which can be 0 (if the timer handler wasn't running when we stopped the governor) or 1 (if the timer handler was running while stopping the governor)).
Hope this clarifies it.
+static void dbs_timer_handler(unsigned long data) +{
- struct cpu_dbs_info *cdbs = (struct cpu_dbs_info *)data;
- struct cpu_common_dbs_info *shared = cdbs->shared;
- struct cpufreq_policy *policy;
- unsigned long flags;
- spin_lock_irqsave(&shared->timer_lock, flags);
- policy = shared->policy;
Why do we need policy here?
- /*
* Timer handler isn't allowed to queue work at the moment, because:* - Another timer handler has done that* - We are stopping the governor* - Or we are updating the sampling rate of ondemand governor*/- if (shared->skip_work)
goto unlock;- shared->skip_work++;
- queue_work(system_wq, &shared->work);
unlock:
What about writing the above as
if (!shared->work_in_progress) { shared->work_in_progress = true; queue_work(system_wq, &shared->work); }
and then you won't need the unlock label.
Here is a diff for that:
diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c index a3f9bc9b98e9..c9e420bd0eec 100644 --- a/drivers/cpufreq/cpufreq_governor.c +++ b/drivers/cpufreq/cpufreq_governor.c @@ -265,11 +265,9 @@ static void dbs_timer_handler(unsigned long data) { struct cpu_dbs_info *cdbs = (struct cpu_dbs_info *)data; struct cpu_common_dbs_info *shared = cdbs->shared; - struct cpufreq_policy *policy; unsigned long flags;
spin_lock_irqsave(&shared->timer_lock, flags); - policy = shared->policy;
/* * Timer handler isn't allowed to queue work at the moment, because: @@ -277,13 +275,11 @@ static void dbs_timer_handler(unsigned long data) * - We are stopping the governor * - Or we are updating the sampling rate of ondemand governor */ - if (shared->skip_work) - goto unlock; - - shared->skip_work++; - queue_work(system_wq, &shared->work); + if (!shared->skip_work) { + shared->skip_work++; + queue_work(system_wq, &shared->work); + }
-unlock: spin_unlock_irqrestore(&shared->timer_lock, flags); }
I will resend this patch now.