[PATCH] soft lockup: kill realtime threads before panic

[Spencer Baugh <sbaugh@catern.com>]

From: Joern Engel <joern@logfs.org>

We have observed cases where the soft lockup detector triggered, but no
kernel bug existed.  Instead we had a buggy realtime thread that
monopolized a cpu.  So let's kill the responsible party and not panic
the entire system.

Signed-off-by: Joern Engel <joern@logfs.org>
Signed-off-by: Spencer Baugh <sbaugh@catern.com>
---
 kernel/watchdog.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index a6ffa43..2355bd5 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -428,7 +428,10 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 		}
 
 		add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
-		if (softlockup_panic)
+		if (rt_prio(current->prio)) {
+			pr_emerg("killing realtime thread\n");
+			send_sig(SIGILL, current, 0);
+		} else if (softlockup_panic)
 			panic("softlockup: hung tasks");
 		__this_cpu_write(soft_watchdog_warn, true);
 	} else
-- 
2.4.3