From: Viresh Kumar <viresh.kumar@linaro.org>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org,
ashwin.chaugule@linaro.org,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V2 5/6] cpufreq: governor: replace per-cpu delayed work with timers
Date: Fri, 4 Dec 2015 11:41:01 +0530 [thread overview]
Message-ID: <20151204061101.GA3430@ubuntu> (raw)
In-Reply-To: <10439879.00aCyM9quW@vostro.rjw.lan>
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.
--
viresh
next prev parent reply other threads:[~2015-12-04 6:11 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1449115453.git.viresh.kumar@linaro.org>
2015-12-03 4:07 ` [PATCH V2 1/6] cpufreq: ondemand: Update sampling rate only for concerned policies Viresh Kumar
2015-12-03 4:07 ` [PATCH V2 2/6] cpufreq: ondemand: Work is guaranteed to be pending Viresh Kumar
2015-12-03 4:07 ` [PATCH V2 3/6] cpufreq: governor: Pass policy as argument to ->gov_dbs_timer() Viresh Kumar
2015-12-03 4:07 ` [PATCH V2 4/6] cpufreq: governor: initialize/destroy timer_mutex with 'shared' Viresh Kumar
2015-12-03 4:07 ` [PATCH V2 5/6] cpufreq: governor: replace per-cpu delayed work with timers Viresh Kumar
2015-12-04 1:18 ` Rafael J. Wysocki
2015-12-04 6:11 ` Viresh Kumar [this message]
2015-12-05 2:14 ` Rafael J. Wysocki
2015-12-05 4:10 ` Viresh Kumar
2015-12-07 1:28 ` Rafael J. Wysocki
2015-12-07 7:50 ` Viresh Kumar
2015-12-07 22:43 ` Rafael J. Wysocki
2015-12-07 23:17 ` Rafael J. Wysocki
2015-12-08 0:39 ` [PATCH][experimantal] cpufreq: governor: Use an atomic variable for synchronization Rafael J. Wysocki
2015-12-08 6:59 ` Viresh Kumar
2015-12-08 13:30 ` Rafael J. Wysocki
2015-12-08 13:36 ` Viresh Kumar
2015-12-08 14:19 ` Rafael J. Wysocki
2015-12-08 13:55 ` Viresh Kumar
2015-12-08 14:30 ` Rafael J. Wysocki
2015-12-08 14:56 ` Viresh Kumar
2015-12-08 16:42 ` Rafael J. Wysocki
2015-12-08 16:34 ` Viresh Kumar
2015-12-08 6:46 ` [PATCH V2 5/6] cpufreq: governor: replace per-cpu delayed work with timers Viresh Kumar
2015-12-08 6:56 ` Viresh Kumar
2015-12-08 13:18 ` Rafael J. Wysocki
2015-12-08 13:30 ` Viresh Kumar
2015-12-08 14:04 ` Rafael J. Wysocki
2015-12-04 6:13 ` [PATCH V3 " Viresh Kumar
2015-12-09 2:04 ` [PATCH V4 " Viresh Kumar
2015-12-09 22:06 ` Rafael J. Wysocki
2015-12-10 2:36 ` Viresh Kumar
2015-12-10 22:17 ` Rafael J. Wysocki
2015-12-11 1:42 ` Viresh Kumar
2015-12-03 4:07 ` [PATCH V2 6/6] cpufreq: ondemand: update update_sampling_rate() to make it more efficient Viresh Kumar
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