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: [<ffffffffa0177b08>] snd_ctl_dev_free+0x28/0x60 [snd]
[ 90.994656]
[ 90.994656] but task is already holding lock:
[ 90.994688] (&dev->lock){+.+.+.}, at: [<ffffffffa040db81>] 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] [<ffffffff810b8fa3>] __lock_acquire+0xb43/0x1330
[ 90.995121] [<ffffffff810b9f82>] lock_acquire+0xa2/0x120
[ 90.995182] [<ffffffff816a5b6c>] mutex_lock_nested+0x5c/0x3c0
[ 90.995245] [<ffffffffa0422cca>] em28xx_vol_put_mute+0x1ba/0x1d0 [em28xx_alsa]
[ 90.995309] [<ffffffffa017813d>] snd_ctl_elem_write+0xfd/0x140 [snd]
[ 90.995376] [<ffffffffa01791c2>] snd_ctl_ioctl+0xe2/0x810 [snd]
[ 90.995442] [<ffffffff811db8b0>] do_vfs_ioctl+0x300/0x520
[ 90.995504] [<ffffffff811dbb51>] SyS_ioctl+0x81/0xa0
[ 90.995568] [<ffffffff816b1929>] system_call_fastpath+0x16/0x1b
[ 90.995630]
-> #0 (&card->controls_rwsem){++++.+}:
[ 90.995780] [<ffffffff810b7a47>] check_prevs_add+0x947/0x950
[ 90.995841] [<ffffffff810b8fa3>] __lock_acquire+0xb43/0x1330
[ 90.995901] [<ffffffff810b9f82>] lock_acquire+0xa2/0x120
[ 90.995962] [<ffffffff816a762b>] down_write+0x3b/0xa0
[ 90.996022] [<ffffffffa0177b08>] snd_ctl_dev_free+0x28/0x60 [snd]
[ 90.996088] [<ffffffffa017a255>] snd_device_free+0x65/0x140 [snd]
[ 90.996154] [<ffffffffa017a751>] snd_device_free_all+0x61/0xa0 [snd]
[ 90.996219] [<ffffffffa0173af4>] snd_card_do_free+0x14/0x130 [snd]
[ 90.996283] [<ffffffffa0173f14>] snd_card_free+0x84/0x90 [snd]
[ 90.996349] [<ffffffffa0423397>] em28xx_audio_fini+0x97/0xb0 [em28xx_alsa]
[ 90.996411] [<ffffffffa040dba6>] em28xx_close_extension+0x56/0x90 [em28xx]
[ 90.996475] [<ffffffffa040f639>] em28xx_usb_disconnect+0x79/0x90 [em28xx]
[ 90.996539] [<ffffffff814a06e7>] usb_unbind_interface+0x67/0x1d0
[ 90.996620] [<ffffffff8142920f>] __device_release_driver+0x7f/0xf0
[ 90.996682] [<ffffffff814292a5>] device_release_driver+0x25/0x40
[ 90.996742] [<ffffffff81428b0c>] bus_remove_device+0x11c/0x1a0
[ 90.996801] [<ffffffff81425536>] device_del+0x136/0x1d0
[ 90.996863] [<ffffffff8149e0c0>] usb_disable_device+0xb0/0x290
[ 90.996923] [<ffffffff814930c5>] usb_disconnect+0xb5/0x1d0
[ 90.996984] [<ffffffff81495ab6>] hub_port_connect_change+0xd6/0xad0
[ 90.997044] [<ffffffff814967c3>] hub_events+0x313/0x9b0
[ 90.997105] [<ffffffff81496e95>] hub_thread+0x35/0x170
[ 90.997165] [<ffffffff8108ea2f>] kthread+0xff/0x120
[ 90.997226] [<ffffffff816b187c>] 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: [<ffffffff81496564>] hub_events+0xb4/0x9b0
[ 90.998025] #1: (&__lockdep_no_validate__){......}, at: [<ffffffff81493076>] usb_disconnect+0x66/0x1d0
[ 90.998204] #2: (&__lockdep_no_validate__){......}, at: [<ffffffff8142929d>] device_release_driver+0x1d/0x40
[ 90.998383] #3: (em28xx_devlist_mutex){+.+.+.}, at: [<ffffffffa040db77>] em28xx_close_extension+0x27/0x90 [em28xx]
[ 90.998567] #4: (&dev->lock){+.+.+.}, at: [<ffffffffa040db81>] em28xx_close_extension+0x31/0x90 [em28xx]
Signed-off-by: Mauro Carvalho Chehab <m.chehab@xxxxxxxxxxx>
---
drivers/media/usb/em28xx/em28xx-core.c | 2 --
drivers/media/usb/em28xx/em28xx-video.c | 4 ++++
2 files changed, 4 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 004fe12ceec7..258628877951 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("Disconnecting video extension");
+ mutex_lock(&dev->lock);
+
v4l2_device_disconnect(&dev->v4l2_dev);
em28xx_uninit_usb_xfer(dev, EM28XX_ANALOG_MODE);
@@ -1924,6 +1926,8 @@ static int em28xx_v4l2_fini(struct em28xx *dev)
v4l2_ctrl_handler_free(&dev->ctrl_handler);
v4l2_device_unregister(&dev->v4l2_dev);
+ mutex_unlock(&dev->lock);
+
kref_put(&dev->ref, em28xx_free_device);
return 0;
--
1.8.3.1
--
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