highmem: Fix race in debug_kmap_atomic() which could cause warn_count…

… to underflow debug_kmap_atomic() tries to prevent ever printing more than 10 warnings, but it does so by testing whether an unsigned integer is equal to 0. However, if the warning is caused by a nested IRQ, then this counter may underflow and the stream of warnings will never end. Fix that by using a signed integer instead. Signed-off-by: Soeren Sandmann Pedersen <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: [email protected] Cc: <[email protected]> # .31.x LKML-Reference: <[email protected]> Signed-off-by: Ingo Molnar <[email protected]>
josf · Nov 10, 2009 · 5ebd4c2 · 5ebd4c2
1 parent 83f5b01
commit 5ebd4c2
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/mm/highmem.c b/mm/highmem.c
@@ -426,9 +426,9 @@ void __init page_address_init(void)
 
 void debug_kmap_atomic(enum km_type type)
 {
-	static unsigned warn_count = 10;
+	static int warn_count = 10;
 
-	if (unlikely(warn_count == 0))
+	if (unlikely(warn_count < 0))
 		return;
 
 	if (unlikely(in_interrupt())) {