From: Viresh Kumar <viresh.kumar@linaro.org>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: linux-pm@vger.kernel.org, linaro-kernel@lists.linaro.org,
ashwin.chaugule@linaro.org,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH][experimantal] cpufreq: governor: Use an atomic variable for synchronization
Date: Tue, 8 Dec 2015 22:04:02 +0530 [thread overview]
Message-ID: <20151208163402.GL3692@ubuntu> (raw)
In-Reply-To: <5332935.yle75kNJGs@vostro.rjw.lan>
On 08-12-15, 17:42, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Subject: [PATCH] cpufreq: governor: Use lockless timer function
>
> It is possible to get rid of the timer_lock spinlock used by the
> governor timer function for synchronization, but a couple of races
> need to be avoided.
>
> The first race is between multiple dbs_timer_handler() instances
> that may be running in parallel with each other on different
> CPUs. Namely, one of them has to queue up the work item, but it
> cannot be queued up more than once. To achieve that,
> atomic_inc_return() can be used on the skip_work field of
> struct cpu_common_dbs_info.
>
> The second race is between an already running dbs_timer_handler()
> and gov_cancel_work(). In that case the dbs_timer_handler() might
> not notice the skip_work incrementation in gov_cancel_work() and
> it might queue up its work item after gov_cancel_work() had
> returned (and that work item would corrupt skip_work going
> forward). To prevent that from happening, gov_cancel_work()
> can be made wait for the timer function to complete (on all CPUs)
> right after skip_work has been incremented.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
> drivers/cpufreq/cpufreq_governor.c | 49 ++++++++++++++++---------------------
> drivers/cpufreq/cpufreq_governor.h | 9 +-----
> 2 files changed, 24 insertions(+), 34 deletions(-)
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
--
viresh
next prev parent reply other threads:[~2015-12-08 16:34 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
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 [this message]
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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