Name: Hotplug CPU Remove for PPC
Author: Rusty Russell
Status: Experimental
Depends: Hotcpu/hotcpu-cpudown.patch.gz Hotcpu/wake_idle_cpu.patch.gz

D: This introduces hotplug CPU capability for PPC.

diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .19474-linux-2.5.34/arch/ppc/kernel/idle.c .19474-linux-2.5.34.updated/arch/ppc/kernel/idle.c
--- .19474-linux-2.5.34/arch/ppc/kernel/idle.c	2002-07-25 10:13:03.000000000 +1000
+++ .19474-linux-2.5.34.updated/arch/ppc/kernel/idle.c	2002-09-10 15:23:33.000000000 +1000
@@ -23,6 +23,8 @@
 #include <linux/unistd.h>
 #include <linux/ptrace.h>
 #include <linux/slab.h>
+#include <linux/brlock.h>
+#include <linux/percpu.h>
 
 #include <asm/pgtable.h>
 #include <asm/uaccess.h>
@@ -95,14 +97,45 @@ void default_idle(void)
 #endif /* CONFIG_PPC_ISERIES */
 }
 
+DECLARE_PER_CPU(int, cpu_die);
+static void die_cpu_die(void)
+{
+	preempt_disable();
+	printk("Cpu %u Dust Dust Dust\n", smp_processor_id());
+	/* Ack it */
+	__get_cpu_var(cpu_die) = 2;
+
+	/* Death loop */
+	local_irq_disable();
+	while (__get_cpu_var(cpu_die))
+		mb();
+
+#if 0 /* FIXME */
+	/* Now, we missed any cache flush IPIs, so be safe. */
+	local_flush_tlb();
+#endif
+	local_irq_enable();
+
+	/* Ack it by setting online bit */
+	br_write_lock_irq(BR_CPU_LOCK);
+	set_bit(smp_processor_id(), cpu_online_map);
+	br_write_unlock_irq(BR_CPU_LOCK);
+	printk("Cpu %u arisen\n", smp_processor_id());
+	preempt_enable();
+}
+
 /*
  * SMP entry into the idle task - calls the same thing as the
  * non-smp versions. -- Cort
  */
 int cpu_idle(void)
 {
-	for (;;)
+	for (;;) {
 		default_idle();
+
+		if (unlikely(__get_cpu_var(cpu_die)))
+			die_cpu_die();
+	}
 	return 0; 
 }
 
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .19474-linux-2.5.34/arch/ppc/kernel/smp.c .19474-linux-2.5.34.updated/arch/ppc/kernel/smp.c
--- .19474-linux-2.5.34/arch/ppc/kernel/smp.c	2002-09-10 15:21:22.000000000 +1000
+++ .19474-linux-2.5.34.updated/arch/ppc/kernel/smp.c	2002-09-10 15:21:43.000000000 +1000
@@ -24,6 +24,8 @@
 #include <linux/init.h>
 #include <linux/spinlock.h>
 #include <linux/cache.h>
+#include <linux/brlock.h>
+#include <linux/percpu.h>
 
 #include <asm/ptrace.h>
 #include <asm/atomic.h>
@@ -389,6 +391,10 @@ int __cpu_up(unsigned int cpu)
 	char buf[32];
 	int c;
 
+	/* FIXME: we don't take it fully down ATM. --RR */
+	if (cpu_callin_map[cpu])
+		goto up;
+
 	/* create a process for the processor */
 	/* only regs.msr is actually used, and 0 is OK for it */
 	memset(&regs, 0, sizeof(struct pt_regs));
@@ -432,21 +438,43 @@ int __cpu_up(unsigned int cpu)
 	printk("Processor %d found.\n", cpu);
 
 	smp_ops->give_timebase();
+ up:
 	br_write_lock_irq(BR_CPU_LOCK);
-	set_bit(cpu, &cpu_online_map);
+	set_bit(cpu, cpu_online_map);
 	br_write_unlock_irq(BR_CPU_LOCK);
 	return 0;
 }
 
-int __cpu_disable(unsigned int cpu)
+int __cpu_disable(void)
 {
 	return -ENOSYS;
 }
 
-/* Since we fail __cpu_disable, this is never called. */
+DEFINE_PER_CPU(int, cpu_die);
+
 void __cpu_die(unsigned int cpu)
 {
-	BUG();
+	unsigned int i;
+
+	printk("Killing cpu %u (%p)\n", cpu, &per_cpu(cpu_die, cpu));
+	/* Final threads can take some time to actually clean up */
+	while (!idle_cpu(cpu))
+		yield();
+
+	per_cpu(cpu_die, cpu) = 1;
+	wmb();
+	wake_idle_cpu(cpu);
+	printk("Waiting for cpu %u\n", cpu);
+	for (i = 0; i < 100; i++) {	
+		rmb();
+		if (per_cpu(cpu_die, cpu) == 2) {
+			printk("cpu %u says its dead\n", cpu);
+			return;
+		}
+		current->state = TASK_INTERRUPTIBLE;
+		schedule_timeout(HZ);
+	}
+	printk("cpu %u didn't die.... hmm...\n", cpu);
 }
 
 void smp_cpus_done(unsigned int max_cpus)