Messages in this thread Patch in this message |  | | Subject | Re: [PATCH] sched/debug: Reset watchdog on all CPUs while processing sysrq-t | From | "liwei (GF)" <> | Date | Fri, 3 Jan 2020 09:54:44 +0800 |
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Hi Steven, Yes, it can be triggered on the Hi1620 system (128 cores) as follows: stress-ng -c 50 & stress-ng -m 50 & stress-ng -i 20 & echo 7 > /proc/sys/kernel/printk echo t > /proc/sysrq-trigger
Then a soft lockup will be reported at migration thread [39636.303531] watchdog: BUG: soft lockup - CPU#67 stuck for 23s! [migration/67:348] which is waiting for the CPU handling sysrq-t to process stop_two_cpus.
Thanks, Wei
On 2020/1/3 3:45, Steven Rostedt wrote: > On Thu, 26 Dec 2019 16:52:24 +0800 > Wei Li <liwei391@huawei.com> wrote: > >> Lengthy output of sysrq-t may take a lot of time on slow serial console >> with lots of processes and CPUs. >> >> So we need to reset NMI-watchdog to avoid spurious lockup messages, and >> we also reset softlockup watchdogs on all other CPUs since another CPU >> might be blocked waiting for us to process an IPI or stop_machine. > > Have you had this triggered? > >> >> Add to sysrq_sched_debug_show() as what we did in show_state_filter(). >> >> Signed-off-by: Wei Li <liwei391@huawei.com> >> --- >> kernel/sched/debug.c | 11 +++++++++-- >> 1 file changed, 9 insertions(+), 2 deletions(-) >> >> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c >> index f7e4579e746c..879d3ccf3806 100644 >> --- a/kernel/sched/debug.c >> +++ b/kernel/sched/debug.c >> @@ -751,9 +751,16 @@ void sysrq_sched_debug_show(void) >> int cpu; >> >> sched_debug_header(NULL); >> - for_each_online_cpu(cpu) >> + for_each_online_cpu(cpu) { >> + /* >> + * Need to reset softlockup watchdogs on all CPUs, because >> + * another CPU might be blocked waiting for us to process >> + * an IPI or stop_machine. >> + */ >> + touch_nmi_watchdog(); >> + touch_all_softlockup_watchdogs(); > > This doesn't seem to hurt to add, thus. > > Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org> > > -- Steve > >> print_cpu(NULL, cpu); >> - >> + } >> } >> >> /* > > > . >
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