From: Viresh Kumar <viresh.kumar@linaro.org>
To: Juri Lelli <juri.lelli@arm.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
Rafael Wysocki <rjw@rjwysocki.net>,
Lists linaro-kernel <linaro-kernel@lists.linaro.org>,
"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
Saravana Kannan <skannan@codeaurora.org>,
Peter Zijlstra <peterz@infradead.org>,
Michael Turquette <mturquette@baylibre.com>,
Steve Muckle <steve.muckle@linaro.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Morten Rasmussen <morten.rasmussen@arm.com>,
dietmar.eggemann@arm.com,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/5] cpufreq: governor: Create separate sysfs-ops
Date: Wed, 3 Feb 2016 12:03:42 +0530 [thread overview]
Message-ID: <20160203063342.GT31828@vireshk> (raw)
In-Reply-To: <20160202170144.GL3947@e106622-lin>
On 02-02-16, 17:01, Juri Lelli wrote:
> Hi Rafael,
>
> On 02/02/16 17:35, Rafael J. Wysocki wrote:
> > On Tue, Feb 2, 2016 at 4:47 PM, Juri Lelli <juri.lelli@arm.com> wrote:
> > > This patch cleans things up a lot, that's good.
> > >
> > > One thing I'm still concerned about, though: don't we need some locking
> > > in place for some of the store operations on governors attributes? Are
> > > store_{ignore_nice_load, sampling_down_fact, etc} safe without locking?
> >
> > That would require some investigation I suppose.
Yeah, that protection is required. Sorry about that.
> > > It seems that we can call them from different cpus concurrently.
> >
> > Yes, we can.
> >
> > One quick-and-dirty way of dealing with that might be to introduce a
> > "sysfs lock" into struct dbs_data and hold that around the invocation
> > of gattr->store() in the sysfs_ops's ->store callback.
s/dirty/sane ? :)
> Can't we actually try to use the policy->rwsem (or one of the core
> locks) + wait_for_completion approach as we do in cpufreq core?
policy->rwsem will defeat the purpose of this change as it will
reintroduce the ABBA issue.
--
viresh
next prev parent reply other threads:[~2016-02-03 6:33 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-02 10:57 [PATCH 0/5] cpufreq: governors: Solve the ABBA lockups Viresh Kumar
2016-02-02 10:57 ` [PATCH 1/5] cpufreq: governor: Kill declare_show_sampling_rate_min() Viresh Kumar
2016-02-02 20:23 ` Rafael J. Wysocki
2016-02-03 2:29 ` Viresh Kumar
2016-02-02 10:57 ` [PATCH 2/5] cpufreq: governor: Create separate sysfs-ops Viresh Kumar
2016-02-02 15:47 ` Juri Lelli
2016-02-02 16:35 ` Rafael J. Wysocki
2016-02-02 17:01 ` Juri Lelli
2016-02-02 19:40 ` Rafael J. Wysocki
2016-02-02 22:21 ` Saravana Kannan
2016-02-02 23:42 ` Rafael J. Wysocki
2016-02-03 1:07 ` Rafael J. Wysocki
2016-02-03 1:32 ` Saravana Kannan
2016-02-03 1:52 ` Rafael J. Wysocki
2016-02-03 4:03 ` Saravana Kannan
2016-02-03 6:57 ` Viresh Kumar
2016-02-03 20:07 ` Saravana Kannan
2016-02-03 6:54 ` Viresh Kumar
2016-02-03 10:51 ` Juri Lelli
2016-02-03 10:55 ` Viresh Kumar
2016-02-03 20:14 ` Saravana Kannan
2016-02-03 6:51 ` Viresh Kumar
2016-02-03 6:33 ` Viresh Kumar [this message]
2016-02-02 21:23 ` Rafael J. Wysocki
2016-02-03 6:58 ` Viresh Kumar
2016-02-03 12:42 ` Rafael J. Wysocki
2016-02-03 13:21 ` Viresh Kumar
2016-02-03 13:38 ` Rafael J. Wysocki
2016-02-02 10:57 ` [PATCH 3/5] cpufreq: governor: Remove unused sysfs attribute macros Viresh Kumar
2016-02-02 21:34 ` Rafael J. Wysocki
2016-02-02 10:57 ` [PATCH 4/5] cpufreq: Don't drop rwsem before calling CPUFREQ_GOV_POLICY_EXIT Viresh Kumar
2016-02-02 21:53 ` Rafael J. Wysocki
2016-02-03 5:51 ` Viresh Kumar
2016-02-03 12:24 ` Rafael J. Wysocki
2016-02-03 13:09 ` Viresh Kumar
2016-02-02 10:57 ` [PATCH 5/5] cpufreq: Get rid of ->governor_enabled and its lock Viresh Kumar
2016-02-02 16:49 ` Juri Lelli
2016-02-03 6:05 ` Viresh Kumar
2016-02-03 11:05 ` Juri Lelli
2016-02-03 11:08 ` Viresh Kumar
2016-02-02 21:57 ` Rafael J. Wysocki
2016-02-02 11:25 ` [PATCH 0/5] cpufreq: governors: Solve the ABBA lockups Juri Lelli
2016-02-02 20:04 ` Rafael J. Wysocki
2016-02-03 2:22 ` Viresh Kumar
2016-02-03 11:37 ` Viresh Kumar
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