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From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Juri Lelli <juri.lelli@arm.com>,
	Michael Turquette <mturquette@baylibre.com>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	steve.muckle@linaro.org,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Morten Rasmussen <morten.rasmussen@arm.com>,
	dietmar.eggemann@arm.com
Subject: Re: [RFC PATCH 18/19] cpufreq: remove transition_lock
Date: Thu, 21 Jan 2016 00:33:28 +0100	[thread overview]
Message-ID: <CAJZ5v0iGUbwDSUZDEcszeDaekqaF+Eq83TCkDpaDj9q2O1s5aw@mail.gmail.com> (raw)
In-Reply-To: <20160120223809.GZ6357@twins.programming.kicks-ass.net>

On Wed, Jan 20, 2016 at 11:38 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, Jan 20, 2016 at 11:12:45PM +0100, Rafael J. Wysocki wrote:
>> > I would dangle _everything_ off the one driver pointer, that's much
>> > easier.
>>
>> I'm not sure how much easier it is in practice.
>>
>> Even if everything dangles out of the driver pointer, data structures
>> pointed to by those things need not be allocated all in one go by the
>> same entity.  Some of them are allocated by drivers, some of them by
>> the core, at different times.
>
> Yes, I've noticed, some of that is really bonkers.
>
>> The ordering between those allocations
>> and populating the pointers is what matters, not how all that is laid
>> out in memory.
>
> I'm thinking getting that ordering right is easier/more natural, if its
> all contained in one object. But this could be subjective.

I'm trying to look at this from the perspective of making changes.

It should be possible to change the ordering of how the data
structures are populated and pointers set without changing the
existing memory layout of them, which may allow us to minimize the
amount of changes to cpufreq drivers for old hardware (and therefore
generally difficult to test), for example.

Also, this way each individual change may be more limited in scope and
therefore less error prone IMO.

  reply	other threads:[~2016-01-20 23:33 UTC|newest]

Thread overview: 110+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-11 17:35 [RFC PATCH 00/19] cpufreq locking cleanups and documentation Juri Lelli
2016-01-11 17:35 ` [RFC PATCH 01/19] cpufreq: do not expose cpufreq_governor_lock Juri Lelli
2016-01-12  8:56   ` Viresh Kumar
2016-01-11 17:35 ` [RFC PATCH 02/19] cpufreq: merge governor lock and mutex Juri Lelli
2016-01-12  9:00   ` Viresh Kumar
2016-01-11 17:35 ` [RFC PATCH 03/19] cpufreq: kill for_each_policy Juri Lelli
2016-01-12  9:01   ` Viresh Kumar
2016-01-11 17:35 ` [RFC PATCH 04/19] cpufreq: bring data structures close to their locks Juri Lelli
2016-01-11 22:05   ` Peter Zijlstra
2016-01-11 23:03     ` Rafael J. Wysocki
2016-01-12  8:27       ` Peter Zijlstra
2016-01-12 10:43         ` Juri Lelli
2016-01-12 16:47         ` Rafael J. Wysocki
2016-01-11 22:07   ` Peter Zijlstra
2016-01-12  9:27     ` Viresh Kumar
2016-01-12 11:21       ` Juri Lelli
2016-01-12 11:58         ` Peter Zijlstra
2016-01-12 12:36           ` Juri Lelli
2016-01-12 15:26             ` Juri Lelli
2016-01-12 15:58               ` Peter Zijlstra
2016-01-12  9:10   ` Viresh Kumar
2016-01-11 17:35 ` [RFC PATCH 05/19] cpufreq: assert locking when accessing cpufreq_policy_list Juri Lelli
2016-01-12  9:34   ` Viresh Kumar
2016-01-12 11:44     ` Juri Lelli
2016-01-13  5:59       ` Viresh Kumar
2016-01-11 17:35 ` [RFC PATCH 06/19] cpufreq: always access cpufreq_policy_list while holding cpufreq_driver_lock Juri Lelli
2016-01-12  9:57   ` Viresh Kumar
2016-01-12 12:08     ` Juri Lelli
2016-01-13  6:01       ` Viresh Kumar
2016-01-11 17:35 ` [RFC PATCH 07/19] cpufreq: assert locking when accessing cpufreq_governor_list Juri Lelli
2016-01-12 10:01   ` Viresh Kumar
2016-01-12 15:33     ` Juri Lelli
2016-01-11 17:35 ` [RFC PATCH 08/19] cpufreq: fix warning for cpufreq_init_policy unlocked access to cpufreq_governor_list Juri Lelli
2016-01-12 10:09   ` Viresh Kumar
2016-01-12 15:52     ` Juri Lelli
2016-01-13  6:07       ` Viresh Kumar
2016-01-14 16:35         ` Juri Lelli
2016-01-18  5:23           ` Viresh Kumar
2016-01-18 15:19             ` Juri Lelli
2016-01-11 17:35 ` [RFC PATCH 09/19] cpufreq: fix warning for show_scaling_available_governors " Juri Lelli
2016-01-12 10:13   ` Viresh Kumar
2016-01-13 10:25     ` Juri Lelli
2016-01-13 10:32       ` Viresh Kumar
2016-01-11 17:35 ` [RFC PATCH 10/19] cpufreq: assert policy->rwsem is held in cpufreq_set_policy Juri Lelli
2016-01-12 10:15   ` Viresh Kumar
2016-01-11 17:35 ` [RFC PATCH 11/19] cpufreq: assert policy->rwsem is held in __cpufreq_governor Juri Lelli
2016-01-12 10:20   ` Viresh Kumar
2016-01-30  0:33     ` Saravana Kannan
2016-01-30 11:49       ` Rafael J. Wysocki
2016-02-01  6:09         ` Viresh Kumar
2016-02-01 10:22           ` Rafael J. Wysocki
2016-02-01 20:24             ` Saravana Kannan
2016-02-01 21:00               ` Rafael J. Wysocki
2016-02-02  6:36                 ` Viresh Kumar
2016-02-02 21:38                   ` Saravana Kannan
2016-02-02  6:34               ` Viresh Kumar
2016-02-02 21:37                 ` Saravana Kannan
2016-02-03  2:13                   ` Viresh Kumar
2016-02-03  4:04                     ` Saravana Kannan
2016-02-03  5:02                       ` Viresh Kumar
2016-02-03  5:06                         ` Saravana Kannan
2016-02-03  6:59                           ` Viresh Kumar
2016-01-11 17:35 ` [RFC PATCH 12/19] cpufreq: fix locking of policy->rwsem in cpufreq_init_policy Juri Lelli
2016-01-12 10:39   ` Viresh Kumar
2016-01-14 17:58     ` Juri Lelli
2016-01-11 17:35 ` [RFC PATCH 13/19] cpufreq: fix locking of policy->rwsem in cpufreq_offline_prepare Juri Lelli
2016-01-12 10:54   ` Viresh Kumar
2016-01-15 12:37     ` Juri Lelli
2016-01-11 17:35 ` [RFC PATCH 14/19] cpufreq: fix locking of policy->rwsem in cpufreq_offline_finish Juri Lelli
2016-01-12 11:02   ` Viresh Kumar
2016-01-11 17:35 ` [RFC PATCH 15/19] cpufreq: remove useless usage of cpufreq_governor_mutex in __cpufreq_governor Juri Lelli
2016-01-12 11:06   ` Viresh Kumar
2016-01-15 16:30     ` Juri Lelli
2016-01-18  5:50       ` Viresh Kumar
2016-01-19 16:49         ` Juri Lelli
2016-01-20  7:29           ` Viresh Kumar
2016-01-20 10:17             ` Juri Lelli
2016-01-20 10:18               ` Viresh Kumar
2016-01-20 10:27                 ` Juri Lelli
2016-01-20 10:30                   ` Viresh Kumar
2016-01-11 17:35 ` [RFC PATCH 16/19] cpufreq: hold policy->rwsem across CPUFREQ_GOV_POLICY_EXIT Juri Lelli
2016-01-12 11:09   ` Viresh Kumar
2016-01-11 17:35 ` [RFC PATCH 17/19] cpufreq: stop checking for cpufreq_driver being present in cpufreq_cpu_get Juri Lelli
2016-01-12 11:17   ` Viresh Kumar
2016-01-11 17:35 ` [RFC PATCH 18/19] cpufreq: remove transition_lock Juri Lelli
2016-01-12 11:24   ` Viresh Kumar
2016-01-13  0:54     ` Michael Turquette
2016-01-13  6:31       ` Viresh Kumar
     [not found]         ` <20160113182131.1168.45753@quark.deferred.io>
2016-01-14  9:44           ` Juri Lelli
2016-01-14 10:32           ` Viresh Kumar
2016-01-14 13:52             ` Juri Lelli
2016-01-18  5:09               ` Viresh Kumar
2016-01-19 14:00           ` Peter Zijlstra
2016-01-19 14:42             ` Juri Lelli
2016-01-19 15:30               ` Peter Zijlstra
2016-01-19 16:01                 ` Juri Lelli
2016-01-19 19:17                   ` Peter Zijlstra
2016-01-19 19:21                     ` Peter Zijlstra
2016-01-19 21:52                       ` Rafael J. Wysocki
2016-01-20 17:04                         ` Peter Zijlstra
2016-01-20 22:12                           ` Rafael J. Wysocki
2016-01-20 22:38                             ` Peter Zijlstra
2016-01-20 23:33                               ` Rafael J. Wysocki [this message]
2016-01-20 12:59                       ` Juri Lelli
2016-01-11 17:36 ` [RFC PATCH 19/19] cpufreq: documentation: document locking scheme Juri Lelli
2016-01-11 22:45 ` [RFC PATCH 00/19] cpufreq locking cleanups and documentation Rafael J. Wysocki
2016-01-12 10:46   ` Juri Lelli
2016-01-30  0:57 ` Saravana Kannan
2016-02-01  6:02   ` Viresh Kumar
2016-02-01 12:06   ` Juri Lelli

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