From: Jan Beulich <jbeulich@novell.com>
Date: Mon, 4 Aug 2008 13:38:54 +0000 (+0100)
Subject: x86: fix spin_is_contended()
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=7bc069c6bc4ede519a7116be1b9e149a1dbf787a;p=openwrt%2Fstaging%2Fblogic.git

x86: fix spin_is_contended()

The masked difference is what needs to be compared against 1, rather
than the difference of masked values (which can be negative).

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Acked-by: Nick Piggin <npiggin@suse.de>
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/include/asm-x86/spinlock.h b/include/asm-x86/spinlock.h
index 4f9a9861799a..e39c790dbfd2 100644
--- a/include/asm-x86/spinlock.h
+++ b/include/asm-x86/spinlock.h
@@ -65,7 +65,7 @@ static inline int __ticket_spin_is_contended(raw_spinlock_t *lock)
 {
 	int tmp = ACCESS_ONCE(lock->slock);
 
-	return (((tmp >> 8) & 0xff) - (tmp & 0xff)) > 1;
+	return (((tmp >> 8) - tmp) & 0xff) > 1;
 }
 
 static __always_inline void __ticket_spin_lock(raw_spinlock_t *lock)
@@ -127,7 +127,7 @@ static inline int __ticket_spin_is_contended(raw_spinlock_t *lock)
 {
 	int tmp = ACCESS_ONCE(lock->slock);
 
-	return (((tmp >> 16) & 0xffff) - (tmp & 0xffff)) > 1;
+	return (((tmp >> 16) - tmp) & 0xffff) > 1;
 }
 
 static __always_inline void __ticket_spin_lock(raw_spinlock_t *lock)