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authorMauro Carvalho Chehab <mchehab@osg.samsung.com>2016-02-11 10:33:31 -0200
committerMauro Carvalho Chehab <mchehab@osg.samsung.com>2016-02-16 08:40:41 -0200
commitc73bbaa4ec3eb225ffe468f80d45724d0496bf03 (patch)
tree99d5c2efef9c6f452cc8750c8873bbd2514bf275 /include/media/rc-core.h
parenteee7d353a19032b48c0f71504081de84a0ee79d8 (diff)
[media] rc-core: don't lock device at rc_register_device()
The mutex lock at rc_register_device() was added by commit 08aeb7c9a42a ("[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>
Diffstat (limited to 'include/media/rc-core.h')
-rw-r--r--include/media/rc-core.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/media/rc-core.h b/include/media/rc-core.h
index f6494709e230..c41dd7018fa8 100644
--- a/include/media/rc-core.h
+++ b/include/media/rc-core.h
@@ -60,6 +60,7 @@ enum rc_filter_type {
/**
* struct rc_dev - represents a remote control device
* @dev: driver model's view of this device
+ * @initialized: true if the device init has completed
* @sysfs_groups: sysfs attribute groups
* @input_name: name of the input child device
* @input_phys: physical path to the input child device
@@ -121,6 +122,7 @@ enum rc_filter_type {
*/
struct rc_dev {
struct device dev;
+ bool initialized;
const struct attribute_group *sysfs_groups[5];
const char *input_name;
const char *input_phys;

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