powerpc/smp: More generic support for "soft hotplug"
This adds more generic support for doing CPU hotplug with a simple
idle loop and no actual reset of the processors. The generic
smp_generic_kick_cpu() does the hotplug bringup trick if the PACA
shows that the CPU has already been started at boot and we provide
an accessor for the CPU state.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 7bf2187..af7e772 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -70,6 +70,10 @@
static DEFINE_PER_CPU(struct task_struct *, idle_thread_array);
#define get_idle_for_cpu(x) (per_cpu(idle_thread_array, x))
#define set_idle_for_cpu(x, p) (per_cpu(idle_thread_array, x) = (p))
+
+/* State of each CPU during hotplug phases */
+static DEFINE_PER_CPU(int, cpu_state) = { 0 };
+
#else
static struct task_struct *idle_thread_array[NR_CPUS] __cpuinitdata ;
#define get_idle_for_cpu(x) (idle_thread_array[(x)])
@@ -104,12 +108,25 @@
* cpu_start field to become non-zero After we set cpu_start,
* the processor will continue on to secondary_start
*/
- paca[nr].cpu_start = 1;
- smp_mb();
+ if (!paca[nr].cpu_start) {
+ paca[nr].cpu_start = 1;
+ smp_mb();
+ return 0;
+ }
+
+#ifdef CONFIG_HOTPLUG_CPU
+ /*
+ * Ok it's not there, so it might be soft-unplugged, let's
+ * try to bring it back
+ */
+ per_cpu(cpu_state, nr) = CPU_UP_PREPARE;
+ smp_wmb();
+ smp_send_reschedule(nr);
+#endif /* CONFIG_HOTPLUG_CPU */
return 0;
}
-#endif
+#endif /* CONFIG_PPC64 */
static irqreturn_t call_function_action(int irq, void *data)
{
@@ -357,8 +374,6 @@
}
#ifdef CONFIG_HOTPLUG_CPU
-/* State of each CPU during hotplug phases */
-static DEFINE_PER_CPU(int, cpu_state) = { 0 };
int generic_cpu_disable(void)
{
@@ -406,6 +421,11 @@
{
per_cpu(cpu_state, cpu) = CPU_DEAD;
}
+
+int generic_check_cpu_restart(unsigned int cpu)
+{
+ return per_cpu(cpu_state, cpu) == CPU_UP_PREPARE;
+}
#endif
struct create_idle {