linux-kernel - Re: [origin tree boot hang] [PATCH] Revert "early

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Date:	Wed, 23 Sep 2009 17:39:20 -0500
From:	Jason Wessel <jason.wessel@...driver.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Len Brown <lenb@...nel.org>, Greg KH <gregkh@...e.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [origin tree boot hang] [PATCH] Revert "early_printk:Allowmorethan
 one early console"

Ingo Molnar wrote:
> * Jason Wessel <jason.wessel@...driver.com> wrote:
>
>   
>> Ingo Molnar wrote:
>>     
>>> * Ingo Molnar <mingo@...e.hu> wrote:
>>>
>>>
>>>   
>>>       
>>>> The commit point to which the attached config and bootlog belongs is:
>>>>
>>>>   2.6.31-07863-gb64ada6
>>>>
>>>> Reverting:
>>>>
>>>>   c953094: early_printk: Allow more than one early console
>>>>
>>>> solves it.
>>>>     
>>>>         
>>> btw., the boot options are:
>>>
>>> Command line: root=/dev/sda6 earlyprintk=serial,ttyS0,115200 console=ttyS0,115200 debug
>>> initcall_debug apic=verbose sysrq_always_enabled ignore_loglevel 
>>> selinux=0 nmi_watchdog=0 panic=1 3
>>>
>>>   
>>>       
>> AH HA!
>>
>> earlyprintk=serial,ttyS0,115200
>>
>> You are invoking the same device twice which is why you are having 
>> infinite recursion.  It was not obvious to me why the earlyprintk code 
>> would allow "serial" or "ttyS", but perhaps we need to protect for 
>> that?
>>
>> Your boot line should be:
>>
>> earlyprintk=serial,115200
>>
>> OR
>>
>> earlyprintk=ttyS0,115200
>>     
>
> ah, indeed!
>
>   
>> The line you had there before would have been the equivalent of doing:
>>
>> earlyprintk=ttyS0,ttyS0,115200
>>
>> Given this, do we still need to execute the revert your revert?  Or 
>> perhaps do we need to add some protection?
>>     
>
> I have such lines on other boxes too. I'd suggest to add protection if 
> it's not too ugly - the typoed line worked and was pretty natural to do, 
> and the failure mode is nasty enough.
>
> 	Ingo
>   

Perhaps you will consider adding this patch to your tree?   It fixes the
specific case you mentioned.  It will still allow the board to boot and
instead of crashing, print a warning on the second instance.

Thanks,
Jason.



View attachment "0001-early_printk-Protect-against-using-the-same-device-t.patch" of type "text/x-diff" (1349 bytes)