On Monday, September 07, 2015 10:55:43 AM Daniel Wagner wrote: > On 09/05/2015 04:11 AM, Rafael J. Wysocki wrote: > > On Friday, September 04, 2015 03:34:55 PM Daniel Wagner wrote: > >> Instead encode the FREEZE state via the CPU state we allow the > >> interesting subsystems (MCE, microcode) to query the power > >> subsystem directly. > > > > A use case, please. > > The motivation for this change is to reduce the complexity in the > hotplug code. As tried to point out in the cover letter, the FROZEN > bits have only a bunch of users after all those years (2007). So it is > worth to have all the notifier users to handle the FROZEN state? > > Don't know if that counts as use case.
Well, the code you're changing has nothing to do with CPU hotplug and CPU_TASKS_FROZEN. It is about suspend-to-idle. Please grep for suspend_freeze_state and see what it is used for. There is some confusion in the naming, but that is about the freezing of the whole system, while CPU_TASKS_FROZEN is about the freezing of user space. > >> Most notifiers are not interested at all > >> in this information so rather have explicit calls to freeze_active() > >> instead adding complexity to the rest of the users of the CPU > >> notifiers. > > > > Why does it has anything to do with CPU notifiers? > > cpu_{down|up} will call the notifiers with the CPU_TASK_FROZEN bit set > and so most notifiers are doing > > switch (actcion ~CPU_TASK_FROZEN) > > to filter it out because they don't need to handle the system wide > ongoing freeze operations. > > > We don't offline CPUs for suspend-to-idle. > > Sure. As I said the motivation is to reduce the complexity in the > hotplug code. You need to fine a different way to do that. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/