linux-kernel - Re: 2.6.29 boot hang

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Date:	Wed, 01 Apr 2009 10:30:30 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Bjorn Helgaas <bjorn.helgaas@...com>,
	andreas.herrmann3@....com,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: 2.6.29 boot hang

Rusty Russell wrote:
> On Wednesday 01 April 2009 15:21:32 Randy Dunlap wrote:
>> Rusty Russell wrote:
>>> On Wednesday 01 April 2009 07:15:35 Randy Dunlap wrote:
>>>> On a 4-proc x86_64 (HP BladeCenter, AMD CPUs) system, booting 2.6.29
>>>> (or earlier, back to 2.6.28-6921-g873392c) hangs during boot.
>>>>
>>>> git bisect says:
>>>> 873392ca514f87eae39f53b6944caf85b1a047cb is first bad commit
>>>> commit 873392ca514f87eae39f53b6944caf85b1a047cb
>>>> Author: Rusty Russell <rusty@...tcorp.com.au>
>>>> Date:   Wed Dec 31 23:54:56 2008 +1030
>>>>
>>>>     PCI: work_on_cpu: use in drivers/pci/pci-driver.c
>>> ...
>>>
>>>> If I change CONFIG_MICROCODE_AMD=y to CONFIG_MICROCODE_AMD=n & rebuild,
>>>> the kernel boots successfully.
>>> How very very odd.  My first thought was a deadlock with keventd used
>>> by work_on_cpu (changed in latest Linus tree), but the microcode code at
>>> that version doesn't use work_on_cpu.
>> Yep, I thought it a bit odd also.
>>
>>> So I don't think that's it, but this patch should canonically eliminate it:
>>>
>>> Subject: work_on_cpu(): rewrite it to create a kernel thread on demand
>>> From: Andrew Morton <akpm@...ux-foundation.org>
>> This patch doesn't apply to 2.6.29-final, but it does apply to 2.6.29-git8,
> 
> Err, it has 14 line offset.  But here's an adjusted one.

Sorry, I had a patch hunk failure for some (odd) reason.

2.6.29 + this patch still hang during boot for me.  Same symptoms.

Thanks.

> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 1f0c509..08bd795 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -971,20 +971,20 @@ undo:
>  }
>  
>  #ifdef CONFIG_SMP
> -static struct workqueue_struct *work_on_cpu_wq __read_mostly;
>  
>  struct work_for_cpu {
> -	struct work_struct work;
> +	struct completion completion;
>  	long (*fn)(void *);
>  	void *arg;
>  	long ret;
>  };
>  
> -static void do_work_for_cpu(struct work_struct *w)
> +static int do_work_for_cpu(void *_wfc)
>  {
> -	struct work_for_cpu *wfc = container_of(w, struct work_for_cpu, work);
> -
> +	struct work_for_cpu *wfc = _wfc;
>  	wfc->ret = wfc->fn(wfc->arg);
> +	complete(&wfc->completion);
> +	return 0;
>  }
>  
>  /**
> @@ -995,17 +995,23 @@ static void do_work_for_cpu(struct work_struct *w)
>   *
>   * This will return the value @fn returns.
>   * It is up to the caller to ensure that the cpu doesn't go offline.
> + * The caller must not hold any locks which would prevent @fn from completing.
>   */
>  long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
>  {
> -	struct work_for_cpu wfc;
> -
> -	INIT_WORK(&wfc.work, do_work_for_cpu);
> -	wfc.fn = fn;
> -	wfc.arg = arg;
> -	queue_work_on(cpu, work_on_cpu_wq, &wfc.work);
> -	flush_work(&wfc.work);
> -
> +	struct task_struct *sub_thread;
> +	struct work_for_cpu wfc = {
> +		.completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
> +		.fn = fn,
> +		.arg = arg,
> +	};
> +
> +	sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
> +	if (IS_ERR(sub_thread))
> +		return PTR_ERR(sub_thread);
> +	kthread_bind(sub_thread, cpu);
> +	wake_up_process(sub_thread);
> +	wait_for_completion(&wfc.completion);
>  	return wfc.ret;
>  }
>  EXPORT_SYMBOL_GPL(work_on_cpu);
> @@ -1021,8 +1027,4 @@ void __init init_workqueues(void)
>  	hotcpu_notifier(workqueue_cpu_callback, 0);
>  	keventd_wq = create_workqueue("events");
>  	BUG_ON(!keventd_wq);
> -#ifdef CONFIG_SMP
> -	work_on_cpu_wq = create_workqueue("work_on_cpu");
> -	BUG_ON(!work_on_cpu_wq);
> -#endif
>  }


-- 
~Randy
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