[PATCH] i386: add idle notifier

Add a notifier mechanism to the low level idle loop.  You can register a
callback function which gets invoked on entry and exit from the low level idle
loop.  The low level idle loop is defined as the polling loop, low-power call,
or the mwait instruction.  Interrupts processed by the idle thread are not
considered part of the low level loop.

The notifier can be used to measure precisely how much is spent in useless
execution (or low power mode).  The perfmon subsystem uses it to turn on/off
monitoring.

Signed-off-by: stephane eranian <eranian@hpl.hp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Andi Kleen <ak@suse.de>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/asm-i386/processor.h b/include/asm-i386/processor.h
index 11bf899de8aa..edfbe46a5e13 100644
--- a/include/asm-i386/processor.h
+++ b/include/asm-i386/processor.h
@@ -257,6 +257,14 @@ static inline void __mwait(unsigned long eax, unsigned long ecx)
                 : :"a" (eax), "c" (ecx));
 }
 
+static inline void __sti_mwait(unsigned long eax, unsigned long ecx)
+{
+        /* "mwait %eax,%ecx;" */
+        asm volatile(
+                "sti; .byte 0x0f,0x01,0xc9;"
+                : :"a" (eax), "c" (ecx));
+}
+
 extern void mwait_idle_with_hints(unsigned long eax, unsigned long ecx);
 
 /* from system description table in BIOS.  Mostly for MCA use, but