On Tuesday, October 11, 2011, Srivatsa S. Bhat wrote: > On 10/10/2011 08:46 PM, Srivatsa S. Bhat wrote: > > On 10/10/2011 07:56 PM, Peter Zijlstra wrote: > >> On Mon, 2011-10-10 at 18:15 +0530, Srivatsa S. Bhat wrote: > >>>> + /* > >>>> + * Prevent cpu online and suspend/hibernate (including freezer) > >>>> + * operations from running in parallel. Fail cpu online if suspend or > >>>> + * hibernate has already started. > >>>> + */ > >>>> + if (!trylock_pm_sleep()) > >>> > >>> Would it be better to hook into the suspend/hibernate notifiers and > >>> use them to exclude cpu hotplug from suspend/hibernate, instead of > >>> trying to take pm_mutex lock like this? > >>> Peter, I remember you pointing out in another patch's review > >>> (http://thread.gmane.org/gmane.linux.kernel/1198312/focus=1199087) > >>> that introducing more locks in cpu hotplug would be a bad idea. Does that > >>> comment hold here as well, or is this fine? > >> > >> Arguably pm_mutex is already involved in the whole hotplug dance due to > >> suspend using it, that said, I'm not at all familiar with the whole > >> suspend/hibernate side of things. > >> > >> I tried having a quick look this morning but failed to find the actual > >> code. > >> > >> I think it would be good to have an overview of the various locks and a > >> small description of how they interact/nest. > >> > > > > Sure. I'll put together whatever I have understood, in the form of a patch > > to Documentation/power directory and post it tomorrow, for the benefit of > > all. > > > > Here it is, just as promised :-) > http://lkml.org/lkml/2011/10/11/393 Well, I have an idea. Why don't we make drivers/base/cpu.c:store_online() take pm_mutex in addition to calling cpu_hotplug_driver_lock()? This at least will make the interface mutually exclusive with suspend/hibernation. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
