From 37fa8716e2d4c4155205aa4a904835de09edbb88 Mon Sep 17 00:00:00 2001 From: Tomas Melin Date: Tue, 30 Sep 2014 10:32:08 -0300 Subject: [PATCH] [media] rc-main: fix lockdep splash for rc-main lockdep reports a potential circular dependecy deadlock when registering input device. Unlock mutex rc_dev->lock prior to calling ir_raw_event_register to avoid the circular dependency since that function also calls input_register_device and rc_open. ====================================================== [ INFO: possible circular locking dependency detected ] 3.17.0-rc7+ #24 Not tainted ------------------------------------------------------- modprobe/647 is trying to acquire lock: (input_mutex){+.+.+.}, at: [] input_register_device+0x2ba/0x381 but task is already holding lock: (ir_raw_handler_lock){+.+.+.}, at: [] ir_raw_event_register+0x102/0x190 which lock already depends on the new lock. [cut text] other info that might help us debug this: Chain exists of: input_mutex --> &dev->lock --> ir_raw_handler_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(ir_raw_handler_lock); lock(&dev->lock); lock(ir_raw_handler_lock); lock(input_mutex); *** DEADLOCK *** 4 locks held by modprobe/647: #0: (&dev->mutex){......}, at: [] device_lock+0xf/0x11 #1: (&dev->mutex){......}, at: [] device_lock+0xf/0x11 #2: (&dev->lock){+.+.+.}, at: [] rc_register_device+0x55d/0x58a #3: (ir_raw_handler_lock){+.+.+.}, at: [] ir_raw_event_register+0x102/0x190 stack backtrace: CPU: 0 PID: 647 Comm: modprobe Not tainted 3.17.0-rc7+ #24 Call Trace: [] dump_stack+0x46/0x58 [] print_circular_bug+0x1f8/0x209 [] __lock_acquire+0xb54/0xeda [] ? console_unlock+0x34d/0x399 [] lock_acquire+0xd9/0x111 [] ? input_register_device+0x2ba/0x381 [] mutex_lock_interruptible_nested+0x57/0x381 [] ? input_register_device+0x2ba/0x381 [] ? kfree+0x7c/0x96 [] ? input_register_device+0x2ba/0x381 [] ? trace_hardirqs_on+0xd/0xf [] input_register_device+0x2ba/0x381 [] ir_mce_kbd_register+0x109/0x139 [] ir_raw_event_register+0x13d/0x190 [] rc_register_device+0x39e/0x58a [] ? trace_hardirqs_on+0xd/0xf [] nvt_probe+0x5ad/0xd52 [nuvoton_cir] [] ? nvt_resume+0x80/0x80 [nuvoton_cir] [] pnp_device_probe+0x8c/0xa9 [] ? driver_sysfs_add+0x6e/0x93 [] driver_probe_device+0xa1/0x1e3 [] ? driver_probe_device+0x1e3/0x1e3 [] __driver_attach+0x4e/0x6f [] bus_for_each_dev+0x5a/0x8c [] driver_attach+0x19/0x1b [] bus_add_driver+0xf1/0x1d6 [] driver_register+0x87/0xbe [] ? 0xffffffffa0120000 [] pnp_register_driver+0x1c/0x1e [] nvt_init+0x10/0x1000 [nuvoton_cir] [] do_one_initcall+0xea/0x18c [] ? __vunmap+0x9d/0xc7 [] load_module+0x1c21/0x1f2c [] ? show_initstate+0x44/0x44 [] SyS_init_module+0xa2/0xb1 [] system_call_fastpath+0x16/0x1b Signed-off-by: Tomas Melin Signed-off-by: Mauro Carvalho Chehab --- drivers/media/rc/rc-main.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/media/rc/rc-main.c b/drivers/media/rc/rc-main.c index a7991c7d010a..296de853a25d 100644 --- a/drivers/media/rc/rc-main.c +++ b/drivers/media/rc/rc-main.c @@ -1414,7 +1414,10 @@ int rc_register_device(struct rc_dev *dev) ir_raw_init(); raw_init = true; } + /* calls ir_register_device so unlock mutex here*/ + mutex_unlock(&dev->lock); rc = ir_raw_event_register(dev); + mutex_lock(&dev->lock); if (rc < 0) goto out_input; }