Bug in mm/thrash.c function grab_swap_token()

Following bug was uncovered by compiling with '-W' flag: CC mm/thrash.o mm/thrash.c: In function â��grab_swap_tokenâ��: mm/thrash.c:52: warning: comparison of unsigned expression < 0 is always false Variable token_priority is unsigned, so decrementing first and then checking the result does not work; fixed by reversing the test, patch attached (compile tested only). I am not sure if likely() makes much sense in this new situation, but I'll let somebody else to make a decision on that. Signed-off-by: Mika Kukkonen <[email protected]> Cc: Rik van Riel <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
teemow · May 11, 2007 · 7faaa5f · 7faaa5f
1 parent 069f11f
commit 7faaa5f
Showing 1 changed file with 2 additions and 3 deletions.
diff --git a/mm/thrash.c b/mm/thrash.c
@@ -48,9 +48,8 @@ void grab_swap_token(void)
 		if (current_interval < current->mm->last_interval)
 			current->mm->token_priority++;
 		else {
-			current->mm->token_priority--;
-			if (unlikely(current->mm->token_priority < 0))
-				current->mm->token_priority = 0;
+			if (likely(current->mm->token_priority > 0))
+				current->mm->token_priority--;
 		}
 		/* Check if we deserve the token */
 		if (current->mm->token_priority >