Messages in this thread | | | Date | Tue, 24 May 2022 16:59:17 +0530 | From | Viresh Kumar <> | Subject | Re: [PATCH v3] cpufreq: fix race on cpufreq online |
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On 24-05-22, 13:22, Rafael J. Wysocki wrote: > On Tue, May 24, 2022 at 1:15 PM Viresh Kumar <viresh.kumar@linaro.org> wrote: > > > > On 13-05-22, 09:57, Viresh Kumar wrote: > > > On 12-05-22, 12:49, Rafael J. Wysocki wrote: > > > > > > Moreover, I'm not sure why the locking dance in store() is necessary. > > > > > > > > > > commit fdd320da84c6 ("cpufreq: Lock CPU online/offline in cpufreq_register_driver()") > > > > > > > > I get that, but I'm wondering if locking CPU hotplug from store() is > > > > needed at all. I mean, if we are in store(), we are holding an active > > > > reference to the policy kobject, so the policy cannot go away until we > > > > are done anyway. Thus it should be sufficient to use the policy rwsem > > > > for synchronization. > > > > > > I think after the current patchset is applied and we have the inactive > > > policy check in store(), we won't required the dance after all. > > > > I was writing a patch for this and then thought maybe look at mails > > around this time, when you sent the patch, and found the reason why we > > need the locking dance :) > > > > https://lore.kernel.org/lkml/20150729091136.GN7557@n2100.arm.linux.org.uk/
Actually no, this is for the lock in cpufreq_driver_register().
> Well, again, if we are in store(), we are holding a reference to the > policy kobject, so this is not initialization time.
This is the commit which made the change.
commit 4f750c930822 ("cpufreq: Synchronize the cpufreq store_*() routines with CPU hotplug")
-- viresh
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