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

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Message-ID: <20090923213929.GA20204@elte.hu>
Date:	Wed, 23 Sep 2009 23:39:29 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jason Wessel <jason.wessel@...driver.com>
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"


* 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
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