Re: [PATCH] fb: convert lock/unlock_kernel() into local fb mutex

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 5 Aug 2008 07:37:55 +0200 Krzysztof Helt <krzysztof.h1@poczta.fm> wrote:

> From: Krzysztof Helt <krzysztof.h1@wp.pl>
> 
> Change lock_kernel()/unlock_kernel() to local fb mutex.
> Each frame buffer instance has its own mutex.
> 
> The one line try_to_load() function is unrolled to
> request_module() in two places for readability.
> 
> Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
> ---
> 
> The only caveat is that I had to put request_module()
> call outside this new mutex while it was inside the 
> lock_kernel() (inside fb_open()). 

Why did you have to do that?

The request_module() in fb_ioctl() is inside the lock...

> If the request_module() should be called only inside this mutex
> please drop the patch.

No, request_module() doesn't need lock_kernel().

The only possible problem I can see is the sole remaining lock_kernel()
in drivers/video/console/vgacon.c.  The fbcon.c code used to be
serialised against vgacon_do_font_op() via lock_kernel, but with this
change vgacon_do_font_op() can now run concurrently with all the code
which you've put inside fb_info.mutex_lock.  Probably not a problem, but
please check that sometime.

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