[PATCH] x86_64: CPU hotplug support

  Experimental CPU hotplug patch for x86_64
  -----------------------------------------
This supports logical CPU online and offline.
- Test with maxcpus=1, and then kick other cpu's off to test if init code
  is all cleaned up. CONFIG_SCHED_SMT works as well.
- idle threads are forked on demand from keventd threads for clean startup

TBD:
1. Not tested on a real NUMA machine (tested with numa=fake=2)
2. Handle ACPI pieces for physical hotplug support.

Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Acked-by: Andi Kleen <ak@muc.de>
Acked-by: Zwane Mwaikambo <zwane@arm.linux.org.uk>
Signed-off-by: Shaohua.li<shaohua.li@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 29 insertions, 0 deletions

diff --git a/arch/x86_64/kernel/irq.c b/arch/x86_64/kernel/irq.c
index 62b112e4deb..cc3fb85f514 100644
--- a/arch/x86_64/kernel/irq.c
+++ b/arch/x86_64/kernel/irq.c
@@ -14,6 +14,7 @@
 #include <linux/interrupt.h>
 #include <linux/seq_file.h>
 #include <linux/module.h>
+#include <linux/delay.h>
 #include <asm/uaccess.h>
 #include <asm/io_apic.h>
 
@@ -106,3 +107,31 @@ asmlinkage unsigned int do_IRQ(struct pt_regs *regs)
         return 1;
 }
 
+#ifdef CONFIG_HOTPLUG_CPU
+void fixup_irqs(cpumask_t map)
+{
+        unsigned int irq;
+        static int warned;
+
+        for (irq = 0; irq < NR_IRQS; irq++) {
+                cpumask_t mask;
+                if (irq == 2)
+                        continue;
+
+                cpus_and(mask, irq_affinity[irq], map);
+                if (any_online_cpu(mask) == NR_CPUS) {
+                        printk("Breaking affinity for irq %i\n", irq);
+                        mask = map;
+                }
+                if (irq_desc[irq].handler->set_affinity)
+                        irq_desc[irq].handler->set_affinity(irq, mask);
+                else if (irq_desc[irq].action && !(warned++))
+                        printk("Cannot set affinity for irq %i\n", irq);
+        }
+
+        /* That doesn't seem sufficient.  Give it 1ms. */
+        local_irq_enable();
+        mdelay(1);
+        local_irq_disable();
+}
+#endif