[PATCH v2] kernel/trace: fix watchdog soft lockup

From: Anders Roxell
Date: Fri Nov 30 2018 - 09:56:34 EST


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]'
Depending on what the what test gets called from init_trace_selftests()
it stays minutes in the loop.
Rework so that function cond_resched() gets called in the
init_trace_selftests loop.

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

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 5706599ed534..109becbc81ca 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1547,6 +1547,10 @@ static __init int init_trace_selftests(void)
pr_info("Running postponed tracer tests:\n");

list_for_each_entry_safe(p, n, &postponed_selftests, list) {
+ /* This loop can take minutes when sanitizers are enabled, so
+ * lets make sure we allow RCU processing.
+ */
+ cond_resched();
ret = run_tracer_selftest(p->type);
/* If the test fails, then warn and remove from available_tracers */
if (ret < 0) {
--
2.19.2