On Mon, Feb 15, 2016 at 02:36:43PM +0200, Joonas Lahtinen wrote: > Instead of implementing a custom locked reference counting, use lockref. > > Current implementation leads to a deadlock splat on Intel SKL platforms > when lockdep debugging is enabled. > > This is due to few of CPUfreq drivers (including Intel P-state) having this; > policy->rwsem is locked during driver initialization and the functions called > during init that actually apply CPU limits use get_online_cpus (because they > have other calling paths too), which will briefly lock cpu_hotplug.lock to > increase cpu_hotplug.refcount. > > On later calling path, when doing a suspend, when cpu_hotplug_begin() is called > in disable_nonboot_cpus(), callbacks to CPUfreq functions get called after, > which will lock policy->rwsem and cpu_hotplug.lock is already held by > cpu_hotplug_begin() and we do have a potential deadlock scenario reported by > our CI system (though it is a very unlikely one). See the Bugzilla link for more > details. I've been meaning to change the thing into a percpu-rwsem, I just haven't had time to look into the lockdep splat that generated. _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
