linux-kernel - [PATCH] soft lockup: kill realtime threads before panic

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Date:	Tue, 21 Jul 2015 15:07:57 -0700
From:	Spencer Baugh <sbaugh@...ern.com>
To:	Don Zickus <dzickus@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ulrich Obergfell <uobergfe@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Jones <drjones@...hat.com>,
	chai wen <chaiw.fnst@...fujitsu.com>,
	Chris Metcalf <cmetcalf@...hip.com>,
	Stephane Eranian <eranian@...gle.com>,
	linux-kernel@...r.kernel.org (open list)
Cc:	Joern Engel <joern@...estorage.com>,
	Spencer Baugh <Spencer.baugh@...estorage.com>,
	Joern Engel <joern@...fs.org>,
	Spencer Baugh <sbaugh@...ern.com>
Subject: [PATCH] soft lockup: kill realtime threads before panic

From: Joern Engel <joern@...fs.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@...fs.org>
Signed-off-by: Spencer Baugh <sbaugh@...ern.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

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