linux-kernel - Re: Linux 3.4 released

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Date:	Wed, 23 May 2012 21:56:36 +0200
From:	Jörg-Volker Peetz <jvpeetz@....de>
To:	Tejun Heo <tj@...nel.org>
CC:	linux-kernel@...r.kernel.org
Subject: Re: Linux 3.4 released

Tejun Heo wrote, on 05/23/12 20:24:
> Hello, Jörg-Volker.
> 
> Please always use reply-to-all.
> 
> On Tue, May 22, 2012 at 09:50:10PM +0200, Jörg-Volker Peetz wrote:
>> no, changing to  printk(KERN_CRIT "XXX: ...", ...)  in kernel/workqueue.c didn't
>> print anything I could read. Would it appear before the "panic screen"? But I'm
>> not able to scroll back.
>> The Panic screen starts with
> 
> It should appear right above BUG:.  Can you please try the following
> instead?
> 
> Thanks.
> 
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 5abf42f..57c33ef 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -1096,10 +1096,18 @@ queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
>  }
>  EXPORT_SYMBOL_GPL(queue_work_on);
>  
> +#include <linux/uaccess.h>
>  static void delayed_work_timer_fn(unsigned long __data)
>  {
>  	struct delayed_work *dwork = (struct delayed_work *)__data;
>  	struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work);
> +	unsigned long v;
> +
> +	if (probe_kernel_read(&v, &cwq->wq, sizeof(v))) {
> +		printk(KERN_CRIT "XXX delayed_work_timer_fn: cwq %p, fn=%pf\n",
> +		       cwq, dwork->work.func);
> +		return;
> +	}
>  
>  	__queue_work(smp_processor_id(), cwq->wq, &dwork->work);
>  }

Hello Tejun,

thank you for bearing with me. I applied this patch. When starting "guvcvideo"
now, the computer seems to work normally, i.e. this program shows the view from
the built-in USB web-cam on the screen. In the kernel log file it says:

May 23 21:32:33 hostname kernel: XXX delayed_work_timer_fn: cwq
(null), fn=hdmi_repoll_eld

(without line-break).

By the way, don't know if this is related, I have a phenomenon with a spurious
interrupt with every linux version I've used before on this notebook. Half a
minute after starting the system the computer produces approx. 220 lines like

... kernel: hda-intel: spurious response 0x0:0x0, last cmd=0x170503

Now with 3.4.0, I see an additional message right before (the minute before) the
"XXX ..." line:

...kernel: hda_intel: azx_get_response timeout, switching to single_cmd mode:
last cmd=0x003f0900

-- 
Best regards,
Jörg-Volker.

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