From ebbfbc2006700f0b5701fb3efa44b55a09fba5d1 Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Mon, 13 Jan 2014 02:53:44 -0300 Subject: [PATCH] [media] em28xx: push mutex down to extensions on .fini callback MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Avoid circular mutex lock by pushing the dev->lock to the .fini callback on each extension. As em28xx-dvb, em28xx-alsa and em28xx-rc have their own data structures, and don't touch at the common structure during .fini, only em28xx-v4l needs to be locked. [ 90.994317] ====================================================== [ 90.994356] [ INFO: possible circular locking dependency detected ] [ 90.994395] 3.13.0-rc1+ #24 Not tainted [ 90.994427] ------------------------------------------------------- [ 90.994458] khubd/54 is trying to acquire lock: [ 90.994490] (&card->controls_rwsem){++++.+}, at: [] snd_ctl_dev_free+0x28/0x60 [snd] [ 90.994656] [ 90.994656] but task is already holding lock: [ 90.994688] (&dev->lock){+.+.+.}, at: [] em28xx_close_extension+0x31/0x90 [em28xx] [ 90.994843] [ 90.994843] which lock already depends on the new lock. [ 90.994843] [ 90.994874] [ 90.994874] the existing dependency chain (in reverse order) is: [ 90.994905] -> #1 (&dev->lock){+.+.+.}: [ 90.995057] [] __lock_acquire+0xb43/0x1330 [ 90.995121] [] lock_acquire+0xa2/0x120 [ 90.995182] [] mutex_lock_nested+0x5c/0x3c0 [ 90.995245] [] em28xx_vol_put_mute+0x1ba/0x1d0 [em28xx_alsa] [ 90.995309] [] snd_ctl_elem_write+0xfd/0x140 [snd] [ 90.995376] [] snd_ctl_ioctl+0xe2/0x810 [snd] [ 90.995442] [] do_vfs_ioctl+0x300/0x520 [ 90.995504] [] SyS_ioctl+0x81/0xa0 [ 90.995568] [] system_call_fastpath+0x16/0x1b [ 90.995630] -> #0 (&card->controls_rwsem){++++.+}: [ 90.995780] [] check_prevs_add+0x947/0x950 [ 90.995841] [] __lock_acquire+0xb43/0x1330 [ 90.995901] [] lock_acquire+0xa2/0x120 [ 90.995962] [] down_write+0x3b/0xa0 [ 90.996022] [] snd_ctl_dev_free+0x28/0x60 [snd] [ 90.996088] [] snd_device_free+0x65/0x140 [snd] [ 90.996154] [] snd_device_free_all+0x61/0xa0 [snd] [ 90.996219] [] snd_card_do_free+0x14/0x130 [snd] [ 90.996283] [] snd_card_free+0x84/0x90 [snd] [ 90.996349] [] em28xx_audio_fini+0x97/0xb0 [em28xx_alsa] [ 90.996411] [] em28xx_close_extension+0x56/0x90 [em28xx] [ 90.996475] [] em28xx_usb_disconnect+0x79/0x90 [em28xx] [ 90.996539] [] usb_unbind_interface+0x67/0x1d0 [ 90.996620] [] __device_release_driver+0x7f/0xf0 [ 90.996682] [] device_release_driver+0x25/0x40 [ 90.996742] [] bus_remove_device+0x11c/0x1a0 [ 90.996801] [] device_del+0x136/0x1d0 [ 90.996863] [] usb_disable_device+0xb0/0x290 [ 90.996923] [] usb_disconnect+0xb5/0x1d0 [ 90.996984] [] hub_port_connect_change+0xd6/0xad0 [ 90.997044] [] hub_events+0x313/0x9b0 [ 90.997105] [] hub_thread+0x35/0x170 [ 90.997165] [] kthread+0xff/0x120 [ 90.997226] [] ret_from_fork+0x7c/0xb0 [ 90.997287] [ 90.997287] other info that might help us debug this: [ 90.997287] [ 90.997318] Possible unsafe locking scenario: [ 90.997318] [ 90.997348] CPU0 CPU1 [ 90.997378] ---- ---- [ 90.997408] lock(&dev->lock); [ 90.997497] lock(&card->controls_rwsem); [ 90.997607] lock(&dev->lock); [ 90.997697] lock(&card->controls_rwsem); [ 90.997786] [ 90.997786] *** DEADLOCK *** [ 90.997786] [ 90.997817] 5 locks held by khubd/54: [ 90.997847] #0: (&__lockdep_no_validate__){......}, at: [] hub_events+0xb4/0x9b0 [ 90.998025] #1: (&__lockdep_no_validate__){......}, at: [] usb_disconnect+0x66/0x1d0 [ 90.998204] #2: (&__lockdep_no_validate__){......}, at: [] device_release_driver+0x1d/0x40 [ 90.998383] #3: (em28xx_devlist_mutex){+.+.+.}, at: [] em28xx_close_extension+0x27/0x90 [em28xx] [ 90.998567] #4: (&dev->lock){+.+.+.}, at: [] em28xx_close_extension+0x31/0x90 [em28xx] Reviewed-by: Frank Schäfer Tested-by: Antti Palosaari Signed-off-by: Mauro Carvalho Chehab --- drivers/media/usb/em28xx/em28xx-core.c | 2 -- drivers/media/usb/em28xx/em28xx-video.c | 3 +++ 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/media/usb/em28xx/em28xx-core.c b/drivers/media/usb/em28xx/em28xx-core.c index b6dc3327c51c..898fb9bd88a2 100644 --- a/drivers/media/usb/em28xx/em28xx-core.c +++ b/drivers/media/usb/em28xx/em28xx-core.c @@ -1099,12 +1099,10 @@ void em28xx_close_extension(struct em28xx *dev) const struct em28xx_ops *ops = NULL; mutex_lock(&em28xx_devlist_mutex); - mutex_lock(&dev->lock); list_for_each_entry(ops, &em28xx_extension_devlist, next) { if (ops->fini) ops->fini(dev); } - mutex_unlock(&dev->lock); list_del(&dev->devlist); mutex_unlock(&em28xx_devlist_mutex); } diff --git a/drivers/media/usb/em28xx/em28xx-video.c b/drivers/media/usb/em28xx/em28xx-video.c index 1486d4740973..aabcafbdab46 100644 --- a/drivers/media/usb/em28xx/em28xx-video.c +++ b/drivers/media/usb/em28xx/em28xx-video.c @@ -1896,6 +1896,8 @@ static int em28xx_v4l2_fini(struct em28xx *dev) em28xx_info("Closing video extension"); + mutex_lock(&dev->lock); + v4l2_device_disconnect(&dev->v4l2_dev); em28xx_uninit_usb_xfer(dev, EM28XX_ANALOG_MODE); @@ -1926,6 +1928,7 @@ static int em28xx_v4l2_fini(struct em28xx *dev) if (dev->users) em28xx_warn("Device is open ! Memory deallocation is deferred on last close.\n"); + mutex_unlock(&dev->lock); return 0; } -- 2.20.1