From: Prarit Bhargava <prarit@redhat.com>
Subject: [RHEL5.1 PATCH]: BZ 206336 Fix softlockup warnings during sysrq-t
Date: Tue, 3 Apr 2007 11:38:49 -0400
Bugzilla: 206366
Message-Id: <20070403153849.3224.12274.sendpatchset@prarit.boston.redhat.com>
Changelog: [misc] Fix softlockup warnings during sysrq-t


Backport of softlockup watchdog fixes.

Avoids bogus softlockup message when doing sysrq-t output.

Currently in -mm tree as add-touch_all_softlockup_watchdogs.patch .

Resolves BZ 206336.

Successfully tested by me.

diff -urNp -X linux-2.6.18.x86_64/Documentation/dontdiff linux-2.6.18.x86_64.orig/include/linux/sched.h linux-2.6.18.x86_64/include/linux/sched.h
--- linux-2.6.18.x86_64.orig/include/linux/sched.h	2007-03-28 09:53:55.000000000 -0400
+++ linux-2.6.18.x86_64/include/linux/sched.h	2007-04-03 05:24:19.000000000 -0400
@@ -216,6 +216,7 @@ extern void scheduler_tick(void);
 extern void softlockup_tick(void);
 extern void spawn_softlockup_task(void);
 extern void touch_softlockup_watchdog(void);
+extern void touch_all_softlockup_watchdogs(void);
 #else
 static inline void softlockup_tick(void)
 {
@@ -226,6 +227,9 @@ static inline void spawn_softlockup_task
 static inline void touch_softlockup_watchdog(void)
 {
 }
+static inline void touch_all_softlockup_watchdogs(void)
+{
+}
 #endif
 
 
diff -urNp -X linux-2.6.18.x86_64/Documentation/dontdiff linux-2.6.18.x86_64.orig/kernel/sched.c linux-2.6.18.x86_64/kernel/sched.c
--- linux-2.6.18.x86_64.orig/kernel/sched.c	2007-03-28 09:53:54.000000000 -0400
+++ linux-2.6.18.x86_64/kernel/sched.c	2007-04-03 05:24:19.000000000 -0400
@@ -4803,6 +4803,8 @@ void show_state(void)
 		show_task(p);
 	} while_each_thread(g, p);
 
+	touch_all_softlockup_watchdogs();
+
 	read_unlock(&tasklist_lock);
 	debug_show_all_locks();
 }
diff -urNp -X linux-2.6.18.x86_64/Documentation/dontdiff linux-2.6.18.x86_64.orig/kernel/softlockup.c linux-2.6.18.x86_64/kernel/softlockup.c
--- linux-2.6.18.x86_64.orig/kernel/softlockup.c	2007-03-28 09:53:54.000000000 -0400
+++ linux-2.6.18.x86_64/kernel/softlockup.c	2007-04-03 05:24:19.000000000 -0400
@@ -40,6 +40,16 @@ void touch_softlockup_watchdog(void)
 }
 EXPORT_SYMBOL(touch_softlockup_watchdog);
 
+void touch_all_softlockup_watchdogs(void)
+{
+	int cpu;
+
+	/* Cause each CPU to re-update its timestamp rather than complain */
+	for_each_online_cpu(cpu)
+		per_cpu(touch_timestamp, cpu) = 0;
+}
+EXPORT_SYMBOL(touch_all_softlockup_watchdogs);
+
 /*
  * This callback runs from the timer interrupt, and checks
  * whether the watchdog thread has hung or not: