Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH 2/2] cpufreq: serialize calls to __cpufreq_governor() | Date | Thu, 05 Sep 2013 02:26:10 +0200 |
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On Wednesday, September 04, 2013 04:50:01 PM Stephen Boyd wrote: > On 09/04/13 16:55, Rafael J. Wysocki wrote: > > > > Well, I'm not sure when Viresh is going to be back. > > > > Srivatsa, can you please resend this patch with a proper changelog? > > > > I haven't had a chance to try this out yet, but I was just thinking > about this patch. How is it going to work? If one task opens the file > and another task is taking down the CPU wouldn't we deadlock in the > CPU_DOWN notifier waiting for the kobject to be released? Task 1 will > grab the kobject reference and sleep on the hotplug mutex and task 2 > will put the kobject and wait for the completion, but it won't happen. > At least I think that's what would happen.
Do you mean the completion in sysfs_deactivate()? Yes, we can deadlock there.
Well, I guess the Srivatsa's patch may be salvaged by making it do a "trylock" version of get_online_cpus(), but then I wonder if there's no better way.
Thanks, Rafael
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