---

yaml --- r: 155211 b: refs/heads/master c: 824975e h: refs/heads/master i: 155209: 971bdf0 155207: 937a003 v: v3
git-mirror · Jul 3, 2009 · 8057048 · 8057048
1 parent b9b5cab
commit 8057048
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Showing 2 changed files with 13 additions and 4 deletions.
diff --git a/[refs] b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 69237f94e65d3d7f539f1adb98ef68685c595004
+refs/heads/master: 824975ef190e7dcb77718d1cc2cb53769b16d918
diff --git a/trunk/arch/x86/lib/atomic64_32.c b/trunk/arch/x86/lib/atomic64_32.c
@@ -76,13 +76,22 @@ u64 atomic64_read(atomic64_t *ptr)
  */
 u64 atomic64_add_return(u64 delta, atomic64_t *ptr)
 {
-	u64 old_val, new_val;
+	/*
+	 * Try first with a (probably incorrect) assumption about
+	 * what we have there. We'll do two loops most likely,
+	 * but we'll get an ownership MESI transaction straight away
+	 * instead of a read transaction followed by a
+	 * flush-for-ownership transaction:
+	 */
+	u64 old_val, new_val, real_val = 1ULL << 32;
 
 	do {
-		old_val = atomic_read(ptr);
+		old_val = real_val;
 		new_val = old_val + delta;
 
-	} while (atomic64_cmpxchg(ptr, old_val, new_val) != old_val);
+		real_val = atomic64_cmpxchg(ptr, old_val, new_val);
+
+	} while (real_val != old_val);
 
 	return new_val;
 }