hung_task: decrement sysctl_hung_task_warnings only if it is positive

Since sysctl_hung_task_warnings == -1 is allowed (infinite warnings),
commit 48a6d64 ("hung_task: allow hung_task_panic when
hung_task_warnings is 0") should decrement it only when it is not -1.

This prevents the kernel from ceasing warnings after the first
4294967295 ;)

Signed-off-by: Tetsuo Handa <[email protected]>
Cc: John Siddle <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Tetsuo Handa

kernel/hung_task.c

@@ -106,7 +106,8 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
 	 * complain:
 	 */
 	if (sysctl_hung_task_warnings) {
-		sysctl_hung_task_warnings--;
+		if (sysctl_hung_task_warnings > 0)
+			sysctl_hung_task_warnings--;
 		pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n",
 			t->comm, t->pid, timeout);
 		pr_err("      %s %s %.*s\n",