On Wed, Jun 12, 2013 at 01:25:22PM +1000, Benjamin Herrenschmidt wrote: > On Mon, 2013-06-03 at 18:43 +0800, Zhao Chenhui wrote: > > On Sat, Jun 01, 2013 at 07:49:44AM +1000, Benjamin Herrenschmidt wrote: > > > On Tue, 2013-05-28 at 15:59 +0800, Zhao Chenhui wrote: > > > > Some features depend on the boot cpu, for instance, hibernate/suspend. > > > > So disable hotplug for the boot cpu. > > > > > > Don't we have code to "move" the boot CPU around when that happens ? > > > > > > Ben. > > > > > > > Currently, the code in generic_cpu_disable() likes this: > > > > if (cpu == boot_cpuid) > > > > return -EBUSY; > > But the code in pseries/hotplug-cpu.c doesn't, we just "move" the boot > CPU around when that happens. Any reason we can't do that generically ? > > Cheers, > Ben. >
Some multicore SoCs firstly boot up the cpu0 after warm reset. In some suspend/resume cases, SoC will do a warm reset when resuming. In order to ensure that the suspending and resuming is running on a same cpu, cpu0 should be the last cpu to suspend. Here, cpu0 is the boot_cpuid. -Chenhui > > If the dying cpu is the boot cpu, it will return -EBUSY. In the subsequent > > error handling, > > cpu_notify_nofail(CPU_DOWN_FAILED) in _cpu_down() will be called. > > Unfortunately, some > > cpu notifier callbacks handled CPU_DOWN_PREPARE, but not CPU_DOWN_FAILED, > > such as sched_cpu_inactive(). > > So it will cause issues. > > > > If we set the hotpluggable for the boot cpu, we can prevent user > > applications from disabling the boot cpu. > > > > -Chenhui > > _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
