x86, suspend: Avoid unnecessary smp alternatives switch during suspend/resume

During suspend, we disable all the non boot cpus. And during resume we bring
them all back again. So no need to do alternatives_smp_switch() in between.

On my core 2 based laptop, this speeds up the suspend path by 15msec and the
resume path by 5 msec (suspend/resume speed up differences can be attributed
to the different P-states that the cpu is in during suspend/resume).

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <1290557500.4946.8.camel@sbsiddha-MOBL3.sc.intel.com>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index f6e726f18491..8ccc182069ec 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -386,6 +386,14 @@ out:
 #ifdef CONFIG_PM_SLEEP_SMP
 static cpumask_var_t frozen_cpus;
 
+void __weak arch_disable_nonboot_cpus_begin(void)
+{
+}
+
+void __weak arch_disable_nonboot_cpus_end(void)
+{
+}
+
 int disable_nonboot_cpus(void)
 {
         int cpu, first_cpu, error = 0;
@@ -397,6 +405,7 @@ int disable_nonboot_cpus(void)
          * with the userspace trying to use the CPU hotplug at the same time
          */
         cpumask_clear(frozen_cpus);
+        arch_disable_nonboot_cpus_begin();
 
         printk("Disabling non-boot CPUs ...\n");
         for_each_online_cpu(cpu) {
@@ -412,6 +421,8 @@ int disable_nonboot_cpus(void)
                 }
         }
 
+        arch_disable_nonboot_cpus_end();
+
         if (!error) {
                 BUG_ON(num_online_cpus() > 1);
                 /* Make sure the CPUs won't be enabled by someone else */