[PATCH] hung_task: Allow hung_task_panic when hung_task_warnings is 0.

[jsiddle@redhat.com]

From: John Siddle <jsiddle@redhat.com>

Previously hung_task_panic would not be respected if enabled after
hung_task_warnings had already been decremented to 0.

Permit the kernel to panic if hung_task_panic is enabled after
hung_task_warnings has already been decremented to 0 and another task
hangs for hung_task_timeout_secs seconds.

Check if hung_task_panic is enabled so we don't return prematurely, and
check if hung_task_warnings is non-zero so we don't print the warning
unnecessarily.

Signed-off-by: John Siddle <jsiddle@redhat.com>
---
 kernel/hung_task.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index d234022..938e0a0 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -98,7 +98,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
 
 	trace_sched_process_hang(t);
 
-	if (!sysctl_hung_task_warnings)
+	if (!sysctl_hung_task_warnings && !sysctl_hung_task_panic)
 		return;
 
 	if (sysctl_hung_task_warnings > 0)
@@ -108,16 +108,18 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
 	 * Ok, the task did not get scheduled for more than 2 minutes,
 	 * complain:
 	 */
-	pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n",
-		t->comm, t->pid, timeout);
-	pr_err("      %s %s %.*s\n",
-		print_tainted(), init_utsname()->release,
-		(int)strcspn(init_utsname()->version, " "),
-		init_utsname()->version);
-	pr_err("\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\""
-		" disables this message.\n");
-	sched_show_task(t);
-	debug_show_held_locks(t);
+	if (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",
+			print_tainted(), init_utsname()->release,
+			(int)strcspn(init_utsname()->version, " "),
+			init_utsname()->version);
+		pr_err("\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\""
+			" disables this message.\n");
+		sched_show_task(t);
+		debug_show_held_locks(t);
+	}
 
 	touch_nmi_watchdog();
 
-- 
2.7.4