[PATCH] i386 CPU hotplug

(The i386 CPU hotplug patch provides infrastructure for some work which Pavel
is doing as well as for ACPI S3 (suspend-to-RAM) work which Li Shaohua
<shaohua.li@intel.com> is doing)

The following provides i386 architecture support for safely unregistering and
registering processors during runtime, updated for the current -mm tree.  In
order to avoid dumping cpu hotplug code into kernel/irq/* i dropped the
cpu_online check in do_IRQ() by modifying fixup_irqs().  The difference being
that on cpu offline, fixup_irqs() is called before we clear the cpu from
cpu_online_map and a long delay in order to ensure that we never have any
queued external interrupts on the APICs.  There are additional changes to s390
and ppc64 to account for this change.

1) Add CONFIG_HOTPLUG_CPU
2) disable local APIC timer on dead cpus.
3) Disable preempt around irq balancing to prevent CPUs going down.
4) Print irq stats for all possible cpus.
5) Debugging check for interrupts on offline cpus.
6) Hacky fixup_irqs() to redirect irqs when cpus go off/online.
7) play_dead() for offline cpus to spin inside.
8) Handle offline cpus set in flush_tlb_others().
9) Grab lock earlier in smp_call_function() to prevent CPUs going down.
10) Implement __cpu_disable() and __cpu_die().
11) Enable local interrupts in cpu_enable() after fixup_irqs()
12) Don't fiddle with NMI on dead cpu, but leave intact on other cpus.
13) Program IRQ affinity whilst cpu is still in cpu_online_map on offline.

Signed-off-by: Zwane Mwaikambo <zwane@linuxpower.ca>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 9 insertions, 0 deletions

diff --git a/include/asm-i386/cpu.h b/include/asm-i386/cpu.h
index 002740b21951..e7252c216ca8 100644
--- a/include/asm-i386/cpu.h
+++ b/include/asm-i386/cpu.h
@@ -5,6 +5,7 @@
 #include <linux/cpu.h>
 #include <linux/topology.h>
 #include <linux/nodemask.h>
+#include <linux/percpu.h>
 
 #include <asm/node.h>
 
@@ -16,4 +17,5 @@ extern int arch_register_cpu(int num);
 extern void arch_unregister_cpu(int);
 #endif
 
+DECLARE_PER_CPU(int, cpu_state);
 #endif /* _ASM_I386_CPU_H_ */
diff --git a/include/asm-i386/irq.h b/include/asm-i386/irq.h
index 05b9e61b0a72..e2d8bf23ad70 100644
--- a/include/asm-i386/irq.h
+++ b/include/asm-i386/irq.h
@@ -38,4 +38,8 @@ extern void release_vm86_irqs(struct task_struct *);
 extern int irqbalance_disable(char *str);
 #endif
 
+#ifdef CONFIG_HOTPLUG_CPU
+extern void fixup_irqs(cpumask_t map);
+#endif
+
 #endif /* _ASM_IRQ_H */
diff --git a/include/asm-i386/smp.h b/include/asm-i386/smp.h
index 55ef31f66bbe..507f2fd39a6a 100644
--- a/include/asm-i386/smp.h
+++ b/include/asm-i386/smp.h
@@ -83,6 +83,9 @@ static __inline int logical_smp_processor_id(void)
 }
 
 #endif
+
+extern int __cpu_disable(void);
+extern void __cpu_die(unsigned int cpu);
 #endif /* !__ASSEMBLY__ */
 
 #define NO_PROC_ID              0xFF            /* No processor magic marker */