Re: [PATCH] soft lockup: kill realtime threads before panic

[yalin wang <yalin.wang2010@gmail.com>]

> On Jul 22, 2015, at 06:07, Spencer Baugh <sbaugh@catern.com> wrote:
> 
> From: Joern Engel <joern@logfs.org>
> 
> We have observed cases where the soft lockup detector triggered, but no
> kernel bug existed.  Instead we had a buggy realtime thread that
> monopolized a cpu.  So let's kill the responsible party and not panic
> the entire system.
> 
> Signed-off-by: Joern Engel <joern@logfs.org>
> Signed-off-by: Spencer Baugh <sbaugh@catern.com>
> ---
> kernel/watchdog.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index a6ffa43..2355bd5 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -428,7 +428,10 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
> 		}
> 
> 		add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
> -		if (softlockup_panic)
> +		if (rt_prio(current->prio)) {
> +			pr_emerg("killing realtime thread\n");
> +			send_sig(SIGILL, current, 0);
> +		} else if (softlockup_panic)
> 			panic("softlockup: hung tasks");
> 		__this_cpu_write(soft_watchdog_warn, true);
> 	} else
> -- 
just my advice about this patch,
i think should add PF_KTHREAD condition like this:

if (rt_prio(current->prio) && !(current->flags & PF_KTHREAD)) {
+			pr_emerg("killing realtime thread\n");
+			send_sig(SIGILL, current, 0);
+		} else if (softlockup_panic)

if soft lockup is caused by kthread, should still panic .

Thanks