Mauro Carvalho Chehab c73bbaa4ec [media] rc-core: don't lock device at rc_register_device() ... The mutex lock at rc_register_device() was added by commit 08aeb7c9a4 ("[media] rc: add locking to fix register/show race"). It is meant to avoid race issues when trying to open a sysfs file while the RC register didn't complete. Adding a lock there causes troubles, as detected by the Kernel lock debug instrumentation at the Kernel: ====================================================== [ INFO: possible circular locking dependency detected ] 4.5.0-rc3+ #46 Not tainted ------------------------------------------------------- systemd-udevd/2681 is trying to acquire lock: (s_active#171){++++.+}, at: [<ffffffff8171a115>] kernfs_remove_by_name_ns+0x45/0xa0 but task is already holding lock: (&dev->lock){+.+.+.}, at: [<ffffffffa0724def>] rc_register_device+0xb2f/0x1450 [rc_core] which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&dev->lock){+.+.+.}: [<ffffffff8124817d>] lock_acquire+0x13d/0x320 [<ffffffff822de966>] mutex_lock_nested+0xb6/0x860 [<ffffffffa0721f2b>] show_protocols+0x3b/0x3f0 [rc_core] [<ffffffff81cdaba5>] dev_attr_show+0x45/0xc0 [<ffffffff8171f1b3>] sysfs_kf_seq_show+0x203/0x3c0 [<ffffffff8171a6a1>] kernfs_seq_show+0x121/0x1b0 [<ffffffff81617c71>] seq_read+0x2f1/0x1160 [<ffffffff8171c911>] kernfs_fop_read+0x321/0x460 [<ffffffff815abc20>] __vfs_read+0xe0/0x3d0 [<ffffffff815ae90e>] vfs_read+0xde/0x2d0 [<ffffffff815b1d01>] SyS_read+0x111/0x230 [<ffffffff822e8636>] entry_SYSCALL_64_fastpath+0x16/0x76 -> #0 (s_active#171){++++.+}: [<ffffffff81244f24>] __lock_acquire+0x4304/0x5990 [<ffffffff8124817d>] lock_acquire+0x13d/0x320 [<ffffffff81717d3a>] __kernfs_remove+0x58a/0x810 [<ffffffff8171a115>] kernfs_remove_by_name_ns+0x45/0xa0 [<ffffffff81721592>] remove_files.isra.0+0x72/0x190 [<ffffffff8172174b>] sysfs_remove_group+0x9b/0x150 [<ffffffff81721854>] sysfs_remove_groups+0x54/0xa0 [<ffffffff81cd97d0>] device_remove_attrs+0xb0/0x140 [<ffffffff81cdb27c>] device_del+0x38c/0x6b0 [<ffffffffa0724b8b>] rc_register_device+0x8cb/0x1450 [rc_core] [<ffffffffa1326a7b>] dvb_usb_remote_init+0x66b/0x14d0 [dvb_usb] [<ffffffffa1321c81>] dvb_usb_device_init+0xf21/0x1860 [dvb_usb] [<ffffffffa13517dc>] dib0700_probe+0x14c/0x410 [dvb_usb_dib0700] [<ffffffff81dbb1dd>] usb_probe_interface+0x45d/0x940 [<ffffffff81ce7e7a>] driver_probe_device+0x21a/0xc30 [<ffffffff81ce89b1>] __driver_attach+0x121/0x160 [<ffffffff81ce21bf>] bus_for_each_dev+0x11f/0x1a0 [<ffffffff81ce6cdd>] driver_attach+0x3d/0x50 [<ffffffff81ce5df9>] bus_add_driver+0x4c9/0x770 [<ffffffff81cea39c>] driver_register+0x18c/0x3b0 [<ffffffff81db6e98>] usb_register_driver+0x1f8/0x440 [<ffffffffa074001e>] dib0700_driver_init+0x1e/0x1000 [dvb_usb_dib0700] [<ffffffff810021b1>] do_one_initcall+0x141/0x300 [<ffffffff8144d8eb>] do_init_module+0x1d0/0x5ad [<ffffffff812f27b6>] load_module+0x6666/0x9ba0 [<ffffffff812f5fe8>] SyS_finit_module+0x108/0x130 [<ffffffff822e8636>] entry_SYSCALL_64_fastpath+0x16/0x76 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&dev->lock); lock(s_active#171); lock(&dev->lock); lock(s_active#171); *** DEADLOCK *** 3 locks held by systemd-udevd/2681: #0: (&dev->mutex){......}, at: [<ffffffff81ce8933>] __driver_attach+0xa3/0x160 #1: (&dev->mutex){......}, at: [<ffffffff81ce8941>] __driver_attach+0xb1/0x160 #2: (&dev->lock){+.+.+.}, at: [<ffffffffa0724def>] rc_register_device+0xb2f/0x1450 [rc_core] In this specific case, some error happened during device init, causing IR to be disabled. Let's fix it by adding a var that will tell when the device is initialized. Any calls before that will return a -EINVAL. That should prevent the race issues. Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>		2016-02-16 08:40:41 -02:00
..
acpi	ACPI / CPPC: remove redundant mbox_send_message() declaration	2016-02-03 01:09:52 +01:00
asm-generic	Merge branch 'akpm' (patches from Andrew)	2016-01-21 12:32:08 -08:00
clocksource
crypto	Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6	2016-01-22 11:58:43 -08:00
drm	Merge branch 'drm-fixes-mst' of git://people.freedesktop.org/~airlied/linux into drm-fixes	2016-02-05 15:24:17 +10:00
dt-bindings	[media] tvp5150: add HW input connectors support	2016-02-11 11:11:29 -02:00
keys
kvm
linux	Merge branch 'akpm' (patches from Andrew)	2016-02-05 20:20:07 -08:00
math-emu
media	[media] rc-core: don't lock device at rc_register_device()	2016-02-16 08:40:41 -02:00
memory
misc
net	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2016-02-01 15:56:08 -08:00
pcmcia
ras
rdma	IB/mlx4: Enable send of RoCE QP1 packets with IP/UDP headers	2016-01-19 15:35:01 -05:00
rxrpc
scsi	Initial roundup of 4.5 merge window patches	2016-01-23 18:45:06 -08:00
soc	ARM: SoC driver updates for v4.5	2016-01-20 18:42:30 -08:00
sound	ALSA: rawmidi: Make snd_rawmidi_transmit() race-free	2016-02-03 14:51:28 +01:00
target	Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending	2016-01-20 17:20:53 -08:00
trace	This includes three minor fixes, mostly due to cut-and-paste issues.	2016-01-28 17:00:50 -08:00
uapi	[media] v4l2-ctrls: add V4L2_CID_DV_RX/TX_IT_CONTENT_TYPE controls	2016-02-10 09:30:56 -02:00
video
xen	Merge branch 'for-4.5/drivers' of git://git.kernel.dk/linux-block	2016-01-21 18:19:38 -08:00
Kbuild