[PATCH] x86_64: Add idle notifiers

This adds a new notifier chain that is called with IDLE_START
when a CPU goes idle and IDLE_END when it goes out of idle.
The context can be idle thread or interrupt context.

Since we cannot rely on MONITOR/MWAIT existing the idle
end check currently has to be done in all interrupt
handlers.

They were originally inspired by the similar s390 implementation.

They have a variety of applications:
- They will be needed for CONFIG_NO_IDLE_HZ
- They can be used for oprofile to fix up the missing time
in idle when performance counters don't tick.
- They can be used for better C state management in ACPI
- They could be used for microstate accounting.

This is just infrastructure so far, no users.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/x86_64/kernel/apic.c b/arch/x86_64/kernel/apic.c
index 40cbd60e2d0b..628aebf9f9aa 100644
--- a/arch/x86_64/kernel/apic.c
+++ b/arch/x86_64/kernel/apic.c
@@ -34,6 +34,7 @@
 #include <asm/pgalloc.h>
 #include <asm/mach_apic.h>
 #include <asm/nmi.h>
+#include <asm/idle.h>
 
 int apic_verbosity;
 
@@ -922,6 +923,7 @@ void smp_apic_timer_interrupt(struct pt_regs *regs)
          * Besides, if we don't timer interrupts ignore the global
          * interrupt lock, which is the WrongThing (tm) to do.
          */
+        exit_idle();
         irq_enter();
         smp_local_timer_interrupt(regs);
         irq_exit();
@@ -981,6 +983,7 @@ __init int oem_force_hpet_timer(void)
 asmlinkage void smp_spurious_interrupt(void)
 {
         unsigned int v;
+        exit_idle();
         irq_enter();
         /*
          * Check if this really is a spurious interrupt and ACK it
@@ -1016,6 +1019,7 @@ asmlinkage void smp_error_interrupt(void)
 {
         unsigned int v, v1;
 
+        exit_idle();
         irq_enter();
         /* First tickle the hardware, only then report what went on. -- REW */
         v = apic_read(APIC_ESR);