linux-kernel - Re: 2.6.21-mm1

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Date:	Sun, 6 May 2007 22:44:29 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	Dan Kruchinin <dubalom@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: 2.6.21-mm1

On Sun, May 06, 2007 at 08:33:48AM +0400, Dan Kruchinin wrote:
> > 
> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.21/2.6.21-mm1/
> 
> I have the following message after kernel compilation:
> 
> ---
> ...
> WARNING: init/built-in.o - Section mismatch: reference to .init.text:
> from .text between 'rest_init' (at offset 0x11e) and 'try_name'

Covered in another mail.

> ...
> ...
> WARNING: drivers/dma/async_tx.o - Section mismatch: reference to
> .init.data: from .data after 'channel_table' (at offset 0x20)
> WARNING: drivers/dma/async_tx.o - Section mismatch: reference to
> .init.data: from .data after 'channel_table' (at offset 0x24)
> WARNING: drivers/dma/async_tx.o - Section mismatch: reference to
> .init.data: from .data after 'channel_table' (at offset 0x28)
> WARNING: drivers/dma/async_tx.o - Section mismatch: reference to
> .init.data: from .data after 'channel_table' (at offset 0x2c)
> WARNING: drivers/dma/async_tx.o - Section mismatch: reference to
> .init.data: from .data after 'channel_table' (at offset 0x30)
> WARNING: drivers/dma/async_tx.o - Section mismatch: reference to
> .init.data: from .data after 'channel_table' (at offset 0x34)
> WARNING: drivers/dma/async_tx.o - Section mismatch: reference to
> .init.data: from .data after 'channel_table' (at offset 0x38)
> WARNING: drivers/dma/async_tx.o - Section mismatch: reference to
> .init.data: from .data after 'channel_table' (at offset 0x3c)
> WARNING: drivers/dma/async_tx.o - Section mismatch: reference to
> .init.data: from .data after 'channel_table' (at offset 0x40)
> WARNING: drivers/dma/async_tx.o - Section mismatch: reference to
> .init.data: from .data after 'channel_table' (at offset 0x44)

We have following code:
/* guarantee that calls that happen before init will not find a channel */
static struct chan_ref_percpu __initdata null_chan_ref[NR_CPUS];

static struct chan_ref_percpu *channel_table[] = {
	DMA_TX_ARRAY_INIT(null_chan_ref)
};

The DMA_TX_ARRAY_INIT is some macro obscufation that serves no
real use and just hide a few assignements.
What happens here is that we assign channel_table a value
that are used as cover-up until the real assignment happens
in the init function.
So the only real way to fix this seems to remove the otherwise correct
__initdata mark on null_chan_ref.
Thats one pointer wasted pr. cpu (in total NR_CPUS).

	Sam
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