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From: Anders Roxell <anders.roxell@linaro.org>
To: rostedt@goodmis.org, mingo@redhat.com
Cc: akpm@linux-foundation.org, dvyukov@google.com,
	linux-kernel@vger.kernel.org,
	Anders Roxell <anders.roxell@linaro.org>,
	Arnd Bergmann <arnd@arndb.de>
Subject: [PATCH 2/2] kernel/trace: fix watchdog soft lockup
Date: Wed, 28 Nov 2018 09:13:34 +0100
Message-ID: <20181128081334.18408-1-anders.roxell@linaro.org> (raw)

When building a allmodconfig kernel for arm64 and boot that in qemu,
CONFIG_FTRACE_STARTUP_TEST gets enabled and that takes time so the
watchdog expires and prints out a message like this:
'watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [swapper/0:1]'
Each time the function ftrace_replace_code gets called it stays in that
functions loop for 41424 times.
Rework so that function cond_resched() gets called in the
ftrace_replace_code loop.

Co-developed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
---
 kernel/trace/ftrace.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 5b4f73e4fd56..3f456921dedf 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2426,6 +2426,10 @@ void __weak ftrace_replace_code(int enable)
 
 	do_for_each_ftrace_rec(pg, rec) {
 
+		/* This loop can take minutes when sanitizers are enabled, so
+		 * lets make sure we allow RCU processing.
+		 */
+		cond_resched();
 		if (rec->flags & FTRACE_FL_DISABLED)
 			continue;
 
-- 
2.19.2


             reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-28  8:13 Anders Roxell [this message]
2018-11-28 14:09 ` Steven Rostedt
2018-11-28 22:24   ` Arnd Bergmann
2018-11-29  3:24     ` Steven Rostedt

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