On Sat, Apr 11, 2009 at 01:08:41PM +0200, Andrea Righi wrote: > On Sat, Apr 11, 2009 at 11:00:38AM +0200, Stefan Richter wrote: > > Krzysztof Helt wrote: > > > On Sat, 11 Apr 2009 00:05:22 +0200 > > > Andrea Righi <righi.andrea@xxxxxxxxx> wrote: > > > > > >> mmmh... I may have missed something, but the common fb_mmap() should > > >> acquire mm->mmap_sem and then info->lock, while fb_ioctl() can do that > > >> in reverse order (info->lock first and then mm->mmap_sem) causing the > > >> circular locking dependency. Are you sure that pushing info->lock down > > >> each driver's fb_mmap will fix the problem? > > > > > > Right. The fb_mmap is called with the mmap_sem already held. > > > I will try other possibilities like breaking info->lock() into two > > > mutexex. > > > > I had to deal with interaction of mmap_sem with a driver lock twice yet. > > I solved it cheaply by replacing mutex_lock(driver_mutex) by > > mutex_trylock(driver_mutex). > > > > The obvious drawback is that thic changes kernel behaviour visibly to > > userspace: Under contention, the ioctl/read/write fails with -EAGAIN > > instead of being blocked until the other thread finished its > > ioctl/read/write/mmap on the same fd (if the driver mutex is > > instantiated per fd, like in my case). > > > > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=8449fc3ae58bf8ee5acbd2280754cde67b5db128 > > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=638570b54346f140bc09b986d93e76025d35180f > > > > (In these two drivers, the change of behaviour is irrelevant to real > > userspace clients.) > > I've looked at the code again. I think the main problem here (at last > the last one reported) is that fb_notifier_call_chain() is called with > info->lock held, i.e. in do_fb_ioctl() => FBIOPUT_VSCREENINFO => > fb_set_var() and the some notifier callbacks, like fbcon_event_notify(), > try to re-acquire info->lock again. > > Probably we can just remove the lock/unlock_fb_info() in all the fb > notifier callbacks' and be sure to always call fb_notifier_call_chain() > with info->lock held. > > Something like this (untested). I'll test it later and re-submit if it > makes sense. Tested intelfb and X11 with fbdev. It seems to work fine, but I may be unable to test the mode switching right now: intelfb: Non-CRT device is enabled ( LVDS port ). Disabling mode switching. It would be great if someone could help me to test this patch (against latest Linus' git - no need to revert 66c1ca). Thanks, -Andrea --- fbdev: fix info->lock deadlock in fbcon_event_notify() fb_notifier_call_chain() is called with info->lock held, i.e. in do_fb_ioctl() => FBIOPUT_VSCREENINFO => fb_set_var() and the some notifier callbacks, like fbcon_event_notify(), try to re-acquire info->lock again. Remove the lock/unlock_fb_info() in all the framebuffer notifier callbacks' and be sure to always call fb_notifier_call_chain() with info->lock held. Reported-by: Pavel Roskin <proski@xxxxxxx> Reported-by: Eric Miao <eric.y.miao@xxxxxxxxx> Signed-off-by: Andrea Righi <righi.andrea@xxxxxxxxx> --- drivers/video/backlight/backlight.c | 3 -- drivers/video/backlight/lcd.c | 3 -- drivers/video/console/fbcon.c | 55 ++--------------------------------- drivers/video/fbmem.c | 19 ++++++++++++ 4 files changed, 22 insertions(+), 58 deletions(-) diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c index dd37cbc..157057c 100644 --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -35,8 +35,6 @@ static int fb_notifier_callback(struct notifier_block *self, return 0; bd = container_of(self, struct backlight_device, fb_notif); - if (!lock_fb_info(evdata->info)) - return -ENODEV; mutex_lock(&bd->ops_lock); if (bd->ops) if (!bd->ops->check_fb || @@ -49,7 +47,6 @@ static int fb_notifier_callback(struct notifier_block *self, backlight_update_status(bd); } mutex_unlock(&bd->ops_lock); - unlock_fb_info(evdata->info); return 0; } diff --git a/drivers/video/backlight/lcd.c b/drivers/video/backlight/lcd.c index 0bb13df..b644947 100644 --- a/drivers/video/backlight/lcd.c +++ b/drivers/video/backlight/lcd.c @@ -40,8 +40,6 @@ static int fb_notifier_callback(struct notifier_block *self, if (!ld->ops) return 0; - if (!lock_fb_info(evdata->info)) - return -ENODEV; mutex_lock(&ld->ops_lock); if (!ld->ops->check_fb || ld->ops->check_fb(ld, evdata->info)) { if (event == FB_EVENT_BLANK) { @@ -53,7 +51,6 @@ static int fb_notifier_callback(struct notifier_block *self, } } mutex_unlock(&ld->ops_lock); - unlock_fb_info(evdata->info); return 0; } diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c index 2cd500a..471a9a6 100644 --- a/drivers/video/console/fbcon.c +++ b/drivers/video/console/fbcon.c @@ -2263,9 +2263,12 @@ static void fbcon_generic_blank(struct vc_data *vc, struct fb_info *info, } + if (!lock_fb_info(info)) + return; event.info = info; event.data = ␣ fb_notifier_call_chain(FB_EVENT_CONBLANK, &event); + unlock_fb_info(info); } static int fbcon_blank(struct vc_data *vc, int blank, int mode_switch) @@ -2956,8 +2959,6 @@ static int fbcon_fb_unregistered(struct fb_info *info) { int i, idx; - if (!lock_fb_info(info)) - return -ENODEV; idx = info->node; for (i = first_fb_vc; i <= last_fb_vc; i++) { if (con2fb_map[i] == idx) @@ -2985,8 +2986,6 @@ static int fbcon_fb_unregistered(struct fb_info *info) if (primary_device == idx) primary_device = -1; - unlock_fb_info(info); - if (!num_registered_fb) unregister_con_driver(&fb_con); @@ -3027,11 +3026,8 @@ static int fbcon_fb_registered(struct fb_info *info) { int ret = 0, i, idx; - if (!lock_fb_info(info)) - return -ENODEV; idx = info->node; fbcon_select_primary(info); - unlock_fb_info(info); if (info_idx == -1) { for (i = first_fb_vc; i <= last_fb_vc; i++) { @@ -3152,53 +3148,23 @@ static int fbcon_event_notify(struct notifier_block *self, switch(action) { case FB_EVENT_SUSPEND: - if (!lock_fb_info(info)) { - ret = -ENODEV; - goto done; - } fbcon_suspended(info); - unlock_fb_info(info); break; case FB_EVENT_RESUME: - if (!lock_fb_info(info)) { - ret = -ENODEV; - goto done; - } fbcon_resumed(info); - unlock_fb_info(info); break; case FB_EVENT_MODE_CHANGE: - if (!lock_fb_info(info)) { - ret = -ENODEV; - goto done; - } fbcon_modechanged(info); - unlock_fb_info(info); break; case FB_EVENT_MODE_CHANGE_ALL: - if (!lock_fb_info(info)) { - ret = -ENODEV; - goto done; - } fbcon_set_all_vcs(info); - unlock_fb_info(info); break; case FB_EVENT_MODE_DELETE: mode = event->data; - if (!lock_fb_info(info)) { - ret = -ENODEV; - goto done; - } ret = fbcon_mode_deleted(info, mode); - unlock_fb_info(info); break; case FB_EVENT_FB_UNBIND: - if (!lock_fb_info(info)) { - ret = -ENODEV; - goto done; - } idx = info->node; - unlock_fb_info(info); ret = fbcon_fb_unbind(idx); break; case FB_EVENT_FB_REGISTERED: @@ -3217,29 +3183,14 @@ static int fbcon_event_notify(struct notifier_block *self, con2fb->framebuffer = con2fb_map[con2fb->console - 1]; break; case FB_EVENT_BLANK: - if (!lock_fb_info(info)) { - ret = -ENODEV; - goto done; - } fbcon_fb_blanked(info, *(int *)event->data); - unlock_fb_info(info); break; case FB_EVENT_NEW_MODELIST: - if (!lock_fb_info(info)) { - ret = -ENODEV; - goto done; - } fbcon_new_modelist(info); - unlock_fb_info(info); break; case FB_EVENT_GET_REQ: caps = event->data; - if (!lock_fb_info(info)) { - ret = -ENODEV; - goto done; - } fbcon_get_requirement(info, caps); - unlock_fb_info(info); break; } done: diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c index 2ac32e6..d412a1d 100644 --- a/drivers/video/fbmem.c +++ b/drivers/video/fbmem.c @@ -1097,8 +1097,11 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd, return -EINVAL; con2fb.framebuffer = -1; event.data = &con2fb; + if (!lock_fb_info(info)) + return -ENODEV; event.info = info; fb_notifier_call_chain(FB_EVENT_GET_CONSOLE_MAP, &event); + unlock_fb_info(info); ret = copy_to_user(argp, &con2fb, sizeof(con2fb)) ? -EFAULT : 0; break; case FBIOPUT_CON2FBMAP: @@ -1115,8 +1118,11 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd, break; } event.data = &con2fb; + if (!lock_fb_info(info)) + return -ENODEV; event.info = info; ret = fb_notifier_call_chain(FB_EVENT_SET_CONSOLE_MAP, &event); + unlock_fb_info(info); break; case FBIOBLANK: if (!lock_fb_info(info)) @@ -1521,7 +1527,10 @@ register_framebuffer(struct fb_info *fb_info) registered_fb[i] = fb_info; event.info = fb_info; + if (!lock_fb_info(fb_info)) + return -ENODEV; fb_notifier_call_chain(FB_EVENT_FB_REGISTERED, &event); + unlock_fb_info(fb_info); return 0; } @@ -1555,8 +1564,12 @@ unregister_framebuffer(struct fb_info *fb_info) goto done; } + + if (!lock_fb_info(fb_info)) + return -ENODEV; event.info = fb_info; ret = fb_notifier_call_chain(FB_EVENT_FB_UNBIND, &event); + unlock_fb_info(fb_info); if (ret) { ret = -EINVAL; @@ -1590,6 +1603,8 @@ void fb_set_suspend(struct fb_info *info, int state) { struct fb_event event; + if (!lock_fb_info(info)) + return; event.info = info; if (state) { fb_notifier_call_chain(FB_EVENT_SUSPEND, &event); @@ -1598,6 +1613,7 @@ void fb_set_suspend(struct fb_info *info, int state) info->state = FBINFO_STATE_RUNNING; fb_notifier_call_chain(FB_EVENT_RESUME, &event); } + unlock_fb_info(info); } /** @@ -1667,8 +1683,11 @@ int fb_new_modelist(struct fb_info *info) err = 1; if (!list_empty(&info->modelist)) { + if (!lock_fb_info(info)) + return -ENODEV; event.info = info; err = fb_notifier_call_chain(FB_EVENT_NEW_MODELIST, &event); + unlock_fb_info(info); } return err; _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
