Re: [Linux-fbdev-devel] [PATCH] add mutex to fbdev for fb_mmap locking

[Krzysztof H. <krz...@po...>]

On Mon, 1 Jun 2009 13:38:40 -0700 (PDT)
Linus Torvalds <tor...@li...> wrote:

> 
> 
> On Mon, 1 Jun 2009, Krzysztof Helt wrote:
> > If the revert to BKL is rejected this patch may wait till 2.6.31.
> 
> Ahh, so this one helps clean up locking, but doesn't fix any actual 
> regressions? I was going to ask you about that.
> 

There is a problem with multihead configuration with and without the patch.
I realize that it is late stage of the 2.6.30 so IMO it is not worth pushing it at 
this moment .
The patch is quite an improvement for smem_start/smem_len handling
so it should find its way into the tree.

> Btw - one thing you could try on the whole lockdep front - and I realize 
> that this is a _total_ hack - is to try the patch below.
> 
> The _only_ thing it does is to hide the sysfs_mutex -> mm_lock chain from 
> lockdep, by using the (incorrect) __copy_to_user_inatomic() instead of the 
> (correct) copy_to_user(). But I'd like to hear if that sysfs_mutex in 
> readdir is the only way you can get a chain.
> 

I'll test this.

Best regards,
Krzysztof

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