On Wed, Oct 2, 2019 at 7:41 PM Hsin-Yi Wang <[email protected]> wrote: > > Currently system reboots use arch specific codes (eg. smp_send_stop) to > offline non reboot cpus. Some arch like arm64, arm, and x86... set offline > masks to cpu without really offlining them. Thus it causes some race > condition and kernel warning comes out sometimes when system reboots. We > can do cpu hotplug in migrate_to_reboot_cpu() to avoid this issue. > > Signed-off-by: Hsin-Yi Wang <[email protected]> > --- > kernel warnings at reboot: > [1] https://lore.kernel.org/lkml/[email protected]/ > [2] https://lore.kernel.org/lkml/[email protected]/ > --- > kernel/cpu.c | 35 +++++++++++++++++++++++++++++++++++ > kernel/reboot.c | 18 ------------------ > 2 files changed, 35 insertions(+), 18 deletions(-) > > diff --git a/kernel/cpu.c b/kernel/cpu.c > index fc28e17940e0..2f4d51fe91e3 100644 > --- a/kernel/cpu.c > +++ b/kernel/cpu.c > @@ -31,6 +31,7 @@ > #include <linux/relay.h> > #include <linux/slab.h> > #include <linux/percpu-rwsem.h> > +#include <linux/reboot.h> > > #include <trace/events/power.h> > #define CREATE_TRACE_POINTS > @@ -1366,6 +1367,40 @@ int __boot_cpu_id; > > #endif /* CONFIG_SMP */ > > +void migrate_to_reboot_cpu(void) > +{ > + /* The boot cpu is always logical cpu 0 */ > + int cpu = reboot_cpu; > + > + /* Make certain the cpu I'm about to reboot on is online */ > + if (!cpu_online(cpu)) > + cpu = cpumask_first(cpu_online_mask); > + > + /* Prevent races with other tasks migrating this task */ > + current->flags |= PF_NO_SETAFFINITY; > + > + /* Make certain I only run on the appropriate processor */ > + set_cpus_allowed_ptr(current, cpumask_of(cpu)); > + > + /* Hotplug other cpus if possible */ > + if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
Should use #ifdef CONFIG_HOTPLUG_CPU here. Will fix in the next version if this patch is reasonable. (Reported-by: kbuild test robot <[email protected]>) > + int i, err; > + > + cpu_maps_update_begin(); > + > + for_each_online_cpu(i) { > + if (i == cpu) > + continue; > + err = _cpu_down(i, 0, CPUHP_OFFLINE); > + if (err) > + pr_info("Failed to offline cpu %d\n", i); > + } > + cpu_hotplug_disabled++; > + > + cpu_maps_update_done(); > + } > +} > + > /* Boot processor state steps */ > static struct cpuhp_step cpuhp_hp_states[] = { > [CPUHP_OFFLINE] = { > diff --git a/kernel/reboot.c b/kernel/reboot.c > index c4d472b7f1b4..f0046be34a60 100644 > --- a/kernel/reboot.c > +++ b/kernel/reboot.c > @@ -215,24 +215,6 @@ void do_kernel_restart(char *cmd) > atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd); > } > > -void migrate_to_reboot_cpu(void) > -{ > - /* The boot cpu is always logical cpu 0 */ > - int cpu = reboot_cpu; > - > - cpu_hotplug_disable(); > - > - /* Make certain the cpu I'm about to reboot on is online */ > - if (!cpu_online(cpu)) > - cpu = cpumask_first(cpu_online_mask); > - > - /* Prevent races with other tasks migrating this task */ > - current->flags |= PF_NO_SETAFFINITY; > - > - /* Make certain I only run on the appropriate processor */ > - set_cpus_allowed_ptr(current, cpumask_of(cpu)); > -} > - > /** > * kernel_restart - reboot the system > * @cmd: pointer to buffer containing command to execute for restart > -- > 2.23.0.444.g18eeb5a265-goog >
