linux-kernel - Re: [PATCH] earlyprintk=efi,keep fix

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Message-Id: <20140430125211.cb33039fc1248c953bcc13dc@linux-foundation.org>
Date:	Wed, 30 Apr 2014 12:52:11 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Dave Young <dyoung@...hat.com>
Cc:	matt.fleming@...el.com, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] earlyprintk=efi,keep fix

On Wed, 30 Apr 2014 10:13:03 +0800 Dave Young <dyoung@...hat.com> wrote:

> 
> earlyprintk=efi,keep will cause kernel hangs while freeing initmem like below:
> [    2.826089] VFS: Mounted root (ext4 filesystem) readonly on device 254:2.
> [    2.846592] devtmpfs: mounted
> [    2.856974] Freeing unused kernel memory: 880K (ffffffff817d4000 - ffffffff818b0000)
> 
> It is caused by efi earlyprintk use __init function which will be freed later.
> Such as early_efi_write is marked as __init, also it will use early_ioremap
> which is init function as well.
> 
> To fix this issue, I added one early initcall efi_ioremap_fb which will map the whole
> efi fb for later use. OTOH, adding a wrapper function efi_ioremap which will call
> early_ioremap before ioremap is available.
> 
> With this patch applied efi boot ok with earlyprintk=efi,keep console=efi
> 

CONFIG_DEBUG_SECTION_MISMATCH should have detected this, but
CONFIG_DEBUG_SECTION_MISMATCH doesn't seem to work any more. 
scripts/Makefile.modpost appears to be trying to pass -S to modpost if
CONFIG_DEBUG_SECTION_MISMATCH, but I'm not seeing any warnings.  The
CONFIG_DEBUG_SECTION_MISMATCH Kconfig help is not useful.  What did we
do?

Shudder.  I'll assume Matt will handle this patch?
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