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 <[email protected]> Signed-off-by: Daniel Vetter <[email protected]> Cc: Daniel Vetter <[email protected]> Cc: Claudio Suarez <[email protected]> Cc: Tetsuo Handa <[email protected]> Cc: Thomas Zimmermann <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: Du Cheng <[email protected]> Cc: Sam Ravnborg <[email protected]> Cc: Matthew Wilcox <[email protected]> Cc: William Kucharski <[email protected]> Cc: Alex Deucher <[email protected]> Cc: Zheyu Ma <[email protected]> Cc: Zhen Lei <[email protected]> Cc: Xiyu Yang <[email protected]> --- 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
