On Tue, 24 May 2011 Bruno PrÃmont <bonbons@xxxxxxxxxxxxxxxxx> wrote: > On Tue, 24 May 2011 Fabio Erculiani <lxnay@xxxxxxxxxxx> wrote: > > register_framebuffer() acquires registration_lock, then calls > > do_register_framebuffer() which calls fb_notifier_call_chain() > > which calls fb_open() which calls get_fb_info() which tries > > (at last) to acquire registration_lock again. > > This is a workaround. > > What calls fb_open() instead of just calling fb_info->fbops->fb_open > when it is set? > In other words what kernel handler of fb_notifier chain does file-based > open of the framebuffer or is the event pushed out synchronously to > userspace? Note that fb_info->lock is also taken on both sides: - per definition around all fb_notifier_call_chain() calls - as well in fb_open() to protect fb_info->fb_ops->fb_open call. Bruno > > Signed-off-by: Fabio Erculiani <lxnay@xxxxxxxxxxx> > > --- > > drivers/video/fbmem.c | 13 ++++++++++++- > > 1 files changed, 12 insertions(+), 1 deletions(-) > > > > diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c > > index 5aac00e..b9831a0 100644 > > --- a/drivers/video/fbmem.c > > +++ b/drivers/video/fbmem.c > > @@ -1628,6 +1628,11 @@ static int do_register_framebuffer(struct fb_info *fb_info) > > event.info = fb_info; > > if (!lock_fb_info(fb_info)) > > return -ENODEV; > > + > > + /* FIXME: unlock registration mutex before registration > > + * notification is sent, in order to avoid deadlock. > > + */ > > + mutex_unlock(®istration_lock); > > fb_notifier_call_chain(FB_EVENT_FB_REGISTERED, &event); > > unlock_fb_info(fb_info); > > return 0; > > @@ -1692,7 +1697,13 @@ register_framebuffer(struct fb_info *fb_info) > > > > mutex_lock(®istration_lock); > > ret = do_register_framebuffer(fb_info); > > - mutex_unlock(®istration_lock); > > + if (ret != 0) > > + /* > > + * FIXME: mutex is unlocked only if ret == 0. > > + * This is the second part of the workaround > > + * that prevents deadlocking. > > + */ > > + mutex_unlock(®istration_lock); > > > > return ret; > > } -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
