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

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Message-Id: <CF86E0FB-4803-459E-8F26-435DF0458591@gmail.com>
Date:	Wed, 22 Jul 2015 14:59:16 +0800
From:	yalin wang <yalin.wang2010@...il.com>
To:	Spencer Baugh <sbaugh@...ern.com>
Cc:	Don Zickus <dzickus@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ulrich Obergfell <uobergfe@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Jones <drjones@...hat.com>,
	chai wen <chaiw.fnst@...fujitsu.com>,
	Chris Metcalf <cmetcalf@...hip.com>,
	Stephane Eranian <eranian@...gle.com>,
	open list <linux-kernel@...r.kernel.org>,
	Joern Engel <joern@...estorage.com>,
	Spencer Baugh <Spencer.baugh@...estorage.com>,
	Joern Engel <joern@...fs.org>
Subject: Re: [PATCH] soft lockup: kill realtime threads before panic


> On Jul 22, 2015, at 06:07, Spencer Baugh <sbaugh@...ern.com> wrote:
> 
> From: Joern Engel <joern@...fs.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@...fs.org>
> Signed-off-by: Spencer Baugh <sbaugh@...ern.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



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