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Date:	Thu, 20 Mar 2014 12:46:31 -0400
From:	Joseph Salisbury <joseph.salisbury@...onical.com>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	JBottomley@...allels.com, Nagalakshmi.Nandigama@....com,
	Sreekanth.Reddy@....com, rientjes@...gle.com,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	tj@...nel.org, tglx@...utronix.de, linux-kernel@...r.kernel.org,
	kernel-team@...ts.ubuntu.com, linux-scsi@...r.kernel.org
Subject: Re: please fix FUSION (Was: [v3.13][v3.14][Regression] kthread:makekthread_create()killable)

On 03/19/2014 03:42 PM, Oleg Nesterov wrote:
> On 03/19, Oleg Nesterov wrote:
>> On 03/19, Oleg Nesterov wrote:
>>> But please do not forget that the kernel crashes. Whatever else we do, this
>>> should be fixed anyway. And this should be fixed in driver.
>> drivers/message/fusion/ is obviously buggy.
> Perhaps this is the only problem and Tetsuo is right, this driver
> really needs more than 30 secs to probe...
>
> But if you have a bit of free time, perhaps you can try the stupid
> debugging patch below ;) Not sure it will help, but who knows.
>
> Oleg.

There was some testing done with your test kernel.  The data collected
while running your kernel is available in the bug report:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1276705/comments/58

Thanks again for the assistance!

>
> diff --git a/drivers/message/fusion/mptsas.c b/drivers/message/fusion/mptsas.c
> index 00d339c..5ecc27e 100644
> --- a/drivers/message/fusion/mptsas.c
> +++ b/drivers/message/fusion/mptsas.c
> @@ -5400,12 +5400,16 @@ mptsas_init(void)
>  {
>  	int error;
>  
> +	printk(KERN_CRIT "mptsas_init start\n");
> +	current->flags |= 0x1;
>  	show_mptmod_ver(my_NAME, my_VERSION);
>  
>  	mptsas_transport_template =
>  	    sas_attach_transport(&mptsas_transport_functions);
> -	if (!mptsas_transport_template)
> -		return -ENODEV;
> +	if (!mptsas_transport_template) {
> +		error = -ENODEV;
> +		goto out;
> +	}
>  	mptsas_transport_template->eh_timed_out = mptsas_eh_timed_out;
>  
>  	mptsasDoneCtx = mpt_register(mptscsih_io_done, MPTSAS_DRIVER,
> @@ -5428,6 +5432,9 @@ mptsas_init(void)
>  	if (error)
>  		sas_release_transport(mptsas_transport_template);
>  
> +out:
> +	current->flags &= ~0x1;
> +	printk(KERN_CRIT "mptsas_init end\n");
>  	return error;
>  }
>  
> diff --git a/kernel/kthread.c b/kernel/kthread.c
> index b5ae3ee..78e643d 100644
> --- a/kernel/kthread.c
> +++ b/kernel/kthread.c
> @@ -291,6 +291,13 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
>  	 * the OOM killer while kthreadd is trying to allocate memory for
>  	 * new kernel thread.
>  	 */
> +
> +	if (current->flags & 1) {
> +		pr_crit("mptsas no killable wait: %d %d\n",
> +			signal_pending(current), __fatal_signal_pending(current));
> +		goto wait;
> +	}
> +
>  	if (unlikely(wait_for_completion_killable(&done))) {
>  		/*
>  		 * If I was SIGKILLed before kthreadd (or new kernel thread)
> @@ -303,6 +310,7 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
>  		 * kthreadd (or new kernel thread) will call complete()
>  		 * shortly.
>  		 */
> +wait:
>  		wait_for_completion(&done);
>  	}
>  	task = create->result;
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index b46131e..2b202bd 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2655,6 +2655,14 @@ static void __sched __schedule(void)
>  	unsigned long *switch_count;
>  	struct rq *rq;
>  	int cpu;
> +	bool trace;
> +
> +	trace = (current->flags & 1) && current->state && !(preempt_count() & PREEMPT_ACTIVE);
> +	if (trace) {
> +		pr_crit("mptsas sched: %lx %d %d\n", current->state,
> +			signal_pending(current), __fatal_signal_pending(current));
> +		show_stack(NULL, NULL);
> +	}
>  
>  need_resched:
>  	preempt_disable();
> @@ -2733,6 +2741,11 @@ need_resched:
>  	sched_preempt_enable_no_resched();
>  	if (need_resched())
>  		goto need_resched;
> +
> +	if (trace) {
> +		pr_crit("mptsas wake: %d %d\n",
> +			signal_pending(current), __fatal_signal_pending(current));
> +	}
>  }
>  
>  static inline void sched_submit_work(struct task_struct *tsk)
> diff --git a/kernel/signal.c b/kernel/signal.c
> index 52f881d..d121944 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -1152,6 +1152,11 @@ static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
>  {
>  	int from_ancestor_ns = 0;
>  
> +	if (t->flags & 1) {
> +		pr_crit("mptsas killed %d\n", sig);
> +		sched_show_task(t);
> +	}
> +
>  #ifdef CONFIG_PID_NS
>  	from_ancestor_ns = si_fromuser(info) &&
>  			   !task_pid_nr_ns(current, task_active_pid_ns(t));
>

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