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From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org,
	Preeti U Murthy <preeti@linux.vnet.ibm.com>,
	open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V3 1/5] cpufreq: ondemand: Drop unnecessary locks from update_sampling_rate()
Date: Wed, 28 Oct 2015 05:05:06 +0100	[thread overview]
Message-ID: <9152551.Va141R8GGE@vostro.rjw.lan> (raw)
In-Reply-To: <56084623b2c27372a4c2c598151dd47176c3e26f.1444723240.git.viresh.kumar@linaro.org>

On Tuesday, October 13, 2015 01:39:01 PM Viresh Kumar wrote:
> 'timer_mutex' is required to sync work-handlers of policy->cpus.
> update_sampling_rate() is just canceling the works and queuing them
> again. This isn't protecting anything at all in update_sampling_rate()
> and is not gonna be of any use.
> 
> Even if a work-handler is already running for a CPU,
> cancel_delayed_work_sync() will wait for it to finish.
> 
> Drop these unnecessary locks.
> 
> Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

I'm queuing this up for 4.4, although I think that the changelog is not right.

While at it, what are the race conditions the lock is protecting against?

Thanks,
Rafael


  reply	other threads:[~2015-10-28  3:36 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <cover.1444723240.git.viresh.kumar@linaro.org>
2015-10-13  8:09 ` Viresh Kumar
2015-10-28  4:05   ` Rafael J. Wysocki [this message]
2015-10-28  4:44     ` Viresh Kumar
2015-10-28  5:54       ` Rafael J. Wysocki
2015-10-28  6:43         ` Viresh Kumar
2015-10-28  7:46           ` Rafael J. Wysocki
2015-10-28  8:56             ` Viresh Kumar
2015-10-13  8:09 ` [PATCH V3 2/5] cpufreq: ondemand: update sampling rate immediately Viresh Kumar
2015-10-28  6:28   ` Rafael J. Wysocki
2015-10-28  9:31     ` Viresh Kumar
2015-10-28 15:31       ` Rafael J. Wysocki
2015-10-28 15:28         ` Viresh Kumar
2015-10-28 16:13           ` Rafael J. Wysocki
2015-10-28 15:47             ` Viresh Kumar
2015-10-13  8:09 ` [PATCH V3 3/5] cpufreq: ondemand: queue work for policy->cpus together Viresh Kumar
2015-10-28  6:38   ` Rafael J. Wysocki
2015-10-28  6:46     ` Viresh Kumar
2015-10-28  7:33       ` Rafael J. Wysocki
2015-10-28  8:34         ` Viresh Kumar
2015-10-13  8:09 ` [PATCH V3 4/5] cpufreq: governor: Quit work-handlers early if governor is stopped Viresh Kumar
2015-10-28  7:10   ` Rafael J. Wysocki
2015-10-28  8:25     ` Viresh Kumar
2015-10-28 15:12       ` Rafael J. Wysocki
2015-10-28 14:46         ` Viresh Kumar
2015-10-13  8:09 ` [PATCH V3 5/5] cpufreq: Get rid of ->governor_enabled and its lock Viresh Kumar

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