[PATCH 14/21] fbcon: use lock_fb_info in fbcon_open/release

[Sam Ravnborg]

On Mon, Jan 31, 2022 at 10:05:45PM +0100, Daniel Vetter wrote:
> Now we get to the real motiviation, because fbmem.c insists that
> that's the right lock for these.
> 
> Ofc fbcon.c has a lot more places where it probably should call
> lock_fb_info(). But looking at fbmem.c at least most of these seem to
> be protected by console_lock() too, which is probably what papers over
> any issues.
> 
> Note that this means we're shuffling around a bit the locking sections
> for some of the console takeover and unbind paths, but not all:
> - console binding/unbinding from the console layer never with
> lock_fb_info
> - unbind (as opposed to unlink) never bother with lock_fb_info
> 
> Also the real serialization against set_par and set_pan are still
> doing by wrapping the entire ioctl code in console_lock(). So this
> shuffling shouldn't be worse than what we had from a "can you trigger
> races?" pov, but it's at least clearer.
> 
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Cc: Claudio Suarez <cssk at net-c.es>
> Cc: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp>
> Cc: Thomas Zimmermann <tzimmermann at suse.de>
> Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> Cc: Du Cheng <ducheng2 at gmail.com>
> Cc: Sam Ravnborg <sam at ravnborg.org>
> Cc: Matthew Wilcox <willy at infradead.org>
> Cc: William Kucharski <william.kucharski at oracle.com>
> Cc: Alex Deucher <alexander.deucher at amd.com>
> Cc: Zheyu Ma <zheyuma97 at gmail.com>
> Cc: Zhen Lei <thunder.leizhen at huawei.com>
> Cc: Xiyu Yang <xiyuyang19 at fudan.edu.cn>

Well, the patch does what the commit log says.
Acked-by: Sam Ravnborg <sam at ravnborg.org>