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

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

[Anders Roxell]

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@arndb.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
---
 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

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

[Steven Rostedt]

On Fri, 30 Nov 2018 15:56:22 +0100
Anders Roxell <anders.roxell@linaro.org> wrote:

> 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.
> 

This looks fine to me. Should it be marked for stable, and pushed into
this release cycle, or wait till the next merge window?

-- Steve

> 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/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) {

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

[Anders Roxell]

On Fri, 30 Nov 2018 at 16:18, Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Fri, 30 Nov 2018 15:56:22 +0100
> Anders Roxell <anders.roxell@linaro.org> wrote:
>
> > 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.
> >
>
> This looks fine to me. Should it be marked for stable, and pushed into
> this release cycle, or wait till the next merge window?

Steve, I'm sorry for the late reply and no its not urgent.
Maybe it can make it into v5.2 ?

Cheers,
Anders

>
> -- Steve
>
> > 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/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) {
>