On Tue, Aug 14, 2012 at 7:48 PM, Ralf Baechle [off-list ref] wrote:

On Mon, Aug 13, 2012 at 08:52:24PM +0800, Huacai Chen wrote:

quoted

When poweroff machine, kernel_power_off() call disable_nonboot_cpus().
And if we have HOTPLUG_CPU configured, disable_nonboot_cpus() is not an
empty function but attempt to actually disable the nonboot cpus. Since
system state is SYSTEM_POWER_OFF, play_dead() won't be called and thus
disable_nonboot_cpus() hangs. Therefore, we make this patch to avoid
poweroff failure.

quoted

diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index e9a5fd7..69b17a9 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c

@@ -72,9 +72,7 @@ void __noreturn cpu_idle(void)
                      }
              }
 #ifdef CONFIG_HOTPLUG_CPU
-             if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map) &&
-                 (system_state == SYSTEM_RUNNING ||
-                  system_state == SYSTEM_BOOTING))
+             if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map))

Looks good - but I'm wondering if the "!cpu_isset(cpu, cpu_callin_map)"
can be removed as well?

For X86, IA64, ARM, SPARC64 and most other arch, "!cpu_online(cpu)" is
the only condition of play_dead(). I keep "!cpu_isset(cpu,
cpu_callin_map)" because this does't refuse poweroff and I don't know
why the old condition of play_dead() is so complex.

Also, which -stable branches is this patch applicable?

3.3, 3.4 and 3.5 branch can use it, 3.2 and earlier kernels should do
some small changes.

  Ralf