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

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Date:   Wed, 20 Mar 2019 12:17:29 +0100
From:   Anders Roxell <anders.roxell@...aro.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v2] kernel/trace: fix watchdog soft lockup

On Fri, 30 Nov 2018 at 16:18, Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Fri, 30 Nov 2018 15:56:22 +0100
> Anders Roxell <anders.roxell@...aro.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@...db.de>
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > Signed-off-by: Anders Roxell <anders.roxell@...aro.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) {
>