From 9b6ec945194ee6497e228a8d6b385d906ba6db22 Mon Sep 17 00:00:00 2001
From: Andi Kleen <ak@suse.de>
Date: Tue, 14 Nov 2006 16:57:46 +0100
Subject: [PATCH] --- yaml --- r: 40927 b: refs/heads/master c:
 9446868b5383eb87f76b2d4389dea4bb968a6657 h: refs/heads/master i:   40925:
 6d183d6a56bcf6e1688c8d424ab0902cd58f12ae   40923:
 7669173fe540ee67c2bfb2d2f03bf64ee49a2fef   40919:
 9e7e1f6e56c60815fbe0211665dae94069b1a0ed   40911:
 d1f5127b2958b97e2ef12fde07058ce70265e83f   40895:
 8a2e5c6757b803bd63d30d2d45277a21298e09fa v: v3

---
 [refs]                             | 2 +-
 trunk/arch/x86_64/kernel/process.c | 3 +--
 trunk/include/asm-x86_64/pda.h     | 9 +++++++++
 3 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/[refs] b/[refs]
index c92ff7bc4a6a..4377dd86c1ab 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 8c131af1db510793f87dc43edbc8950a35370df3
+refs/heads/master: 9446868b5383eb87f76b2d4389dea4bb968a6657
diff --git a/trunk/arch/x86_64/kernel/process.c b/trunk/arch/x86_64/kernel/process.c
index 49f7fac6229e..f6226055d53d 100644
--- a/trunk/arch/x86_64/kernel/process.c
+++ b/trunk/arch/x86_64/kernel/process.c
@@ -88,9 +88,8 @@ void enter_idle(void)
 
 static void __exit_idle(void)
 {
-	if (read_pda(isidle) == 0)
+	if (test_and_clear_bit_pda(0, isidle) == 0)
 		return;
-	write_pda(isidle, 0);
 	atomic_notifier_call_chain(&idle_notifier, IDLE_END, NULL);
 }
 
diff --git a/trunk/include/asm-x86_64/pda.h b/trunk/include/asm-x86_64/pda.h
index 14996d962bac..5642634843c4 100644
--- a/trunk/include/asm-x86_64/pda.h
+++ b/trunk/include/asm-x86_64/pda.h
@@ -109,6 +109,15 @@ extern struct x8664_pda _proxy_pda;
 #define sub_pda(field,val) pda_to_op("sub",field,val)
 #define or_pda(field,val) pda_to_op("or",field,val)
 
+/* This is not atomic against other CPUs -- CPU preemption needs to be off */
+#define test_and_clear_bit_pda(bit,field) ({		\
+	int old__;						\
+	asm volatile("btr %2,%%gs:%c3\n\tsbbl %0,%0"		\
+	    : "=r" (old__), "+m" (_proxy_pda.field) 		\
+	    : "dIr" (bit), "i" (pda_offset(field)) : "memory");	\
+	old__;							\
+})
+
 #endif
 
 #define PDA_STACKOFFSET (5*8)