| Message ID | 20190520082216.26273-33-daniel.vetter@ffwll.ch (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | fbcon notifier begone! | expand |
Op 20-05-2019 om 10:22 schreef Daniel Vetter: > It's not pretty. > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> > Cc: Daniel Vetter <daniel.vetter@ffwll.ch> > Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> > Cc: Hans de Goede <hdegoede@redhat.com> > Cc: Yisheng Xie <ysxie@foxmail.com> > --- > drivers/video/fbdev/core/fbcon.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c > index b40b56702c61..cbbcf7a795f2 100644 > --- a/drivers/video/fbdev/core/fbcon.c > +++ b/drivers/video/fbdev/core/fbcon.c > @@ -87,6 +87,25 @@ > # define DPRINTK(fmt, args...) > #endif > > +/* > + * FIXME: Locking > + * > + * - fbcon state itself is protected by the console_lock, and the code does a > + * pretty good job at making sure that lock is held everywhere it's needed. > + * > + * - access to the registered_fb array is entirely unprotected. This should use > + * proper object lifetime handling, i.e. get/put_fb_info. This also means > + * switching from indices to proper pointers for fb_info everywhere. > + * > + * - fbcon doesn't bother with fb_lock/unlock at all. This is buggy, since it > + * means concurrent access to the same fbdev from both fbcon and userspace > + * will blow up. To fix this all fbcon calls from fbmem.c need to be moved out > + * of fb_lock/unlock protected sections, since otherwise we'll recurse and > + * deadlock eventually. Aside: Due to these deadlock issues the fbdev code in > + * fbmem.c cannot use locking asserts, and there's lots of callers which get > + * the rules wrong, e.g. fbsysfs.c entirely missed fb_lock/unlock calls too. > + */ > + > enum { > FBCON_LOGO_CANSHOW = -1, /* the logo can be shown */ > FBCON_LOGO_DRAW = -2, /* draw the logo to a console */ I did a casual review, so for whole series with the small nitpicks I had, and any feedback by others, kbuild and the arm mess being fixed up: Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> However, according to reviewer's statement of oversight: While I have reviewed the patch and believe it to be sound, I do not (unless explicitly stated elsewhere) make any warranties or guarantees that it will achieve its stated purpose or function properly in any given situation. :) ~Maarten
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index b40b56702c61..cbbcf7a795f2 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -87,6 +87,25 @@ # define DPRINTK(fmt, args...) #endif +/* + * FIXME: Locking + * + * - fbcon state itself is protected by the console_lock, and the code does a + * pretty good job at making sure that lock is held everywhere it's needed. + * + * - access to the registered_fb array is entirely unprotected. This should use + * proper object lifetime handling, i.e. get/put_fb_info. This also means + * switching from indices to proper pointers for fb_info everywhere. + * + * - fbcon doesn't bother with fb_lock/unlock at all. This is buggy, since it + * means concurrent access to the same fbdev from both fbcon and userspace + * will blow up. To fix this all fbcon calls from fbmem.c need to be moved out + * of fb_lock/unlock protected sections, since otherwise we'll recurse and + * deadlock eventually. Aside: Due to these deadlock issues the fbdev code in + * fbmem.c cannot use locking asserts, and there's lots of callers which get + * the rules wrong, e.g. fbsysfs.c entirely missed fb_lock/unlock calls too. + */ + enum { FBCON_LOGO_CANSHOW = -1, /* the logo can be shown */ FBCON_LOGO_DRAW = -2, /* draw the logo to a console */
It's not pretty. Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> Cc: Hans de Goede <hdegoede@redhat.com> Cc: Yisheng Xie <ysxie@foxmail.com> --- drivers/video/fbdev/core/fbcon.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)