On Wed, Jan 15, 2020 at 02:34:10PM +0800, Hsin-Yi Wang wrote: > Currently system reboots uses architecture specific codes (smp_send_stop) > to offline non reboot CPUs. Most architecture's implementation is looping > through all non reboot online CPUs and call ipi function to each of them. Some > architecture like arm64, arm, and x86... would set offline masks to cpu without > really offline them. This causes some race condition and kernel warning comes > out sometimes when system reboots. > > This patch adds a config ARCH_OFFLINE_CPUS_ON_REBOOT, which would offline cpus in > migrate_to_reboot_cpu(). If non reboot cpus are all offlined here, the loop for > checking online cpus would be an empty loop. If architecture don't enable this > config, or some cpus somehow fails to offline, it would fallback to ipi > function. > What's the timing impact on systems with large number of CPUs(say 256 or more) ? I remember we added some change to reduce the wait times for offlining CPUs in system suspend path on arm64, still not negligible. -- Regards, Sudeep
