Messages in this thread | | | Date | Thu, 19 May 2016 07:40:23 +0530 | From | Viresh Kumar <> | Subject | Re: [PATCH] cpufreq: Drop the 'initialized' field from struct cpufreq_governor |
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On 18-05-16, 22:59, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > The 'initialized' field in struct cpufreq_governor is only used by > the conservative governor (as a usage counter) and the way that > happens is far from straightforward and arguably incorrect. > > Namely, the value of 'initialized' is checked by > cpufreq_dbs_governor_init() and cpufreq_dbs_governor_exit() and > the results of those checks are passed (as the second argument) to > the ->init() and ->exit() callbacks in struct dbs_governor. Those > callbacks are only implemented by the ondemand and conservative > governors and ondemand doesn't use their second argument at all. > In turn, the conservative governor uses it to decide whether or not > to either register or unregister a transition notifier. > > That whole mechanism is not only unnecessarily convoluted, but also > racy, because the 'initialized' field of struct cpufreq_governor is > updated in cpufreq_init_governor() and cpufreq_exit_governor() under > policy->rwsem which doesn't help if one of these functions is run > twice in parallel for different policies (which isn't impossible in > principle), for example. > > Instead of it, add a proper usage counter to the conservative > governor and update it from cs_init() and cs_exit() which is > guaranteed to be non-racy, as those functions are only called > under gov_dbs_data_mutex which is global. > > With that in place, drop the 'initialized' field from struct > cpufreq_governor as it is not used any more. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > --- > > This is on top of https://patchwork.kernel.org/patch/9094021/ > > --- > drivers/cpufreq/cpufreq.c | 3 -- > drivers/cpufreq/cpufreq_conservative.c | 44 +++++++++++++++++++++------------ > drivers/cpufreq/cpufreq_governor.c | 6 ++-- > drivers/cpufreq/cpufreq_governor.h | 4 +-- > drivers/cpufreq/cpufreq_ondemand.c | 4 +-- > include/linux/cpufreq.h | 1 > 6 files changed, 36 insertions(+), 26 deletions(-)
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
-- viresh
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