[PATCH v2 12/19] fbcon: use lock_fb_info in fbcon_open/release

[Daniel Vetter]

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.

Acked-by: Sam Ravnborg <s...@ravnborg.org>
Signed-off-by: Daniel Vetter <daniel.vet...@intel.com>
Cc: Daniel Vetter <dan...@ffwll.ch>
Cc: Claudio Suarez <c...@net-c.es>
Cc: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
Cc: Thomas Zimmermann <tzimmerm...@suse.de>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Cc: Du Cheng <duche...@gmail.com>
Cc: Sam Ravnborg <s...@ravnborg.org>
Cc: Matthew Wilcox <wi...@infradead.org>
Cc: William Kucharski <william.kuchar...@oracle.com>
Cc: Alex Deucher <alexander.deuc...@amd.com>
Cc: Zheyu Ma <zheyum...@gmail.com>
Cc: Zhen Lei <thunder.leiz...@huawei.com>
Cc: Xiyu Yang <xiyuyan...@fudan.edu.cn>
---
 drivers/video/fbdev/core/fbcon.c | 5 +++++
 drivers/video/fbdev/core/fbmem.c | 4 ----
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index f0213a0e3870..cc960bf49991 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -684,8 +684,10 @@ static int fbcon_invalid_charcount(struct fb_info *info, 
unsigned charcount)
 
 static void fbcon_release(struct fb_info *info)
 {
+       lock_fb_info(info);
        if (info->fbops->fb_release)
                info->fbops->fb_release(info, 0);
+       unlock_fb_info(info);
 
        module_put(info->fbops->owner);
 }
@@ -697,11 +699,14 @@ static int fbcon_open(struct fb_info *info)
        if (!try_module_get(info->fbops->owner))
                return -ENODEV;
 
+       lock_fb_info(info);
        if (info->fbops->fb_open &&
            info->fbops->fb_open(info, 0)) {
+               unlock_fb_info(info);
                module_put(info->fbops->owner);
                return -ENODEV;
        }
+       unlock_fb_info(info);
 
        ops = kzalloc(sizeof(struct fbcon_ops), GFP_KERNEL);
        if (!ops) {
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index ad9aac06427a..37656883e7bd 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1674,9 +1674,7 @@ static int do_register_framebuffer(struct fb_info 
*fb_info)
                console_lock();
        else
                atomic_inc(&ignore_console_lock_warning);
-       lock_fb_info(fb_info);
        ret = fbcon_fb_registered(fb_info);
-       unlock_fb_info(fb_info);
 
        if (!lockless_register_fb)
                console_unlock();
@@ -1693,9 +1691,7 @@ static void unbind_console(struct fb_info *fb_info)
                return;
 
        console_lock();
-       lock_fb_info(fb_info);
        fbcon_fb_unbind(fb_info);
-       unlock_fb_info(fb_info);
        console_unlock();
 }
 
-- 
2.34.1