From db5b15b74ed9a5c04bb808d18ffa2c773f5c18c0 Mon Sep 17 00:00:00 2001 From: Sean Young Date: Mon, 13 Feb 2017 10:35:44 -0200 Subject: [media] lirc: fix dead lock between open and wakeup_filter The locking in lirc needs improvement, but for now just fix this potential deadlock. ====================================================== [ INFO: possible circular locking dependency detected ] 4.10.0-rc1+ #1 Not tainted ------------------------------------------------------- bash/2502 is trying to acquire lock: (ir_raw_handler_lock){+.+.+.}, at: [] ir_raw_encode_scancode+0x3e/0xb0 [rc_core] but task is already holding lock: (&dev->lock){+.+.+.}, at: [] store_filter+0x9f/0x240 [rc_core] which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&dev->lock){+.+.+.}: [] lock_acquire+0xfd/0x200 [] mutex_lock_nested+0x77/0x6d0 [] rc_open+0x2a/0x80 [rc_core] [] lirc_dev_fop_open+0xda/0x1e0 [lirc_dev] [] chrdev_open+0xb0/0x210 [] do_dentry_open+0x20a/0x2f0 [] vfs_open+0x4c/0x80 [] path_openat+0x5bc/0xc00 [] do_filp_open+0x91/0x100 [] do_sys_open+0x130/0x220 [] SyS_open+0x1e/0x20 [] entry_SYSCALL_64_fastpath+0x1f/0xc2 -> #1 (lirc_dev_lock){+.+.+.}: [] lock_acquire+0xfd/0x200 [] mutex_lock_nested+0x77/0x6d0 [] lirc_register_driver+0x67/0x59b [lirc_dev] [] ir_lirc_register+0x1f4/0x260 [ir_lirc_codec] [] ir_raw_handler_register+0x7c/0xb0 [rc_core] [] 0xffffffffc0398010 [] do_one_initcall+0x52/0x1b0 [] do_init_module+0x5f/0x1fa [] load_module+0x2675/0x2b00 [] SYSC_finit_module+0xdf/0x110 [] SyS_finit_module+0xe/0x10 [] do_syscall_64+0x6c/0x1f0 [] return_from_SYSCALL_64+0x0/0x7a -> #0 (ir_raw_handler_lock){+.+.+.}: [] __lock_acquire+0x10f7/0x1290 [] lock_acquire+0xfd/0x200 [] mutex_lock_nested+0x77/0x6d0 [] ir_raw_encode_scancode+0x3e/0xb0 [rc_core] [] loop_set_wakeup_filter+0x62/0xbd [rc_loopback] [] store_filter+0x1aa/0x240 [rc_core] [] dev_attr_store+0x18/0x30 [] sysfs_kf_write+0x45/0x60 [] kernfs_fop_write+0x155/0x1e0 [] __vfs_write+0x37/0x160 [] vfs_write+0xc8/0x1e0 [] SyS_write+0x58/0xc0 [] entry_SYSCALL_64_fastpath+0x1f/0xc2 other info that might help us debug this: Chain exists of: ir_raw_handler_lock --> lirc_dev_lock --> &dev->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&dev->lock); lock(lirc_dev_lock); lock(&dev->lock); lock(ir_raw_handler_lock); *** DEADLOCK *** 4 locks held by bash/2502: #0: (sb_writers#4){.+.+.+}, at: [] vfs_write+0x195/0x1e0 #1: (&of->mutex){+.+.+.}, at: [] kernfs_fop_write+0x11f/0x1e0 #2: (s_active#215){.+.+.+}, at: [] kernfs_fop_write+0x128/0x1e0 #3: (&dev->lock){+.+.+.}, at: [] store_filter+0x9f/0x240 [rc_core] stack backtrace: CPU: 3 PID: 2502 Comm: bash Not tainted 4.10.0-rc1+ #1 Hardware name: /DG45ID, BIOS IDG4510H.86A.0135.2011.0225.1100 02/25/2011 Call Trace: dump_stack+0x86/0xc3 print_circular_bug+0x1be/0x210 __lock_acquire+0x10f7/0x1290 lock_acquire+0xfd/0x200 ? ir_raw_encode_scancode+0x3e/0xb0 [rc_core] ? ir_raw_encode_scancode+0x3e/0xb0 [rc_core] mutex_lock_nested+0x77/0x6d0 ? ir_raw_encode_scancode+0x3e/0xb0 [rc_core] ? loop_set_wakeup_filter+0x44/0xbd [rc_loopback] ir_raw_encode_scancode+0x3e/0xb0 [rc_core] loop_set_wakeup_filter+0x62/0xbd [rc_loopback] ? loop_set_tx_duty_cycle+0x70/0x70 [rc_loopback] store_filter+0x1aa/0x240 [rc_core] dev_attr_store+0x18/0x30 sysfs_kf_write+0x45/0x60 kernfs_fop_write+0x155/0x1e0 __vfs_write+0x37/0x160 ? rcu_read_lock_sched_held+0x4a/0x80 ? rcu_sync_lockdep_assert+0x2f/0x60 ? __sb_start_write+0x10c/0x220 ? vfs_write+0x195/0x1e0 ? security_file_permission+0x3b/0xc0 vfs_write+0xc8/0x1e0 SyS_write+0x58/0xc0 entry_SYSCALL_64_fastpath+0x1f/0xc2 Signed-off-by: Sean Young Signed-off-by: Mauro Carvalho Chehab --- drivers/media/rc/lirc_dev.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'drivers/media/rc/lirc_dev.c') diff --git a/drivers/media/rc/lirc_dev.c b/drivers/media/rc/lirc_dev.c index a54ca531d8ef..4630f3e67538 100644 --- a/drivers/media/rc/lirc_dev.c +++ b/drivers/media/rc/lirc_dev.c @@ -436,6 +436,8 @@ int lirc_dev_fop_open(struct inode *inode, struct file *file) return -ERESTARTSYS; ir = irctls[iminor(inode)]; + mutex_unlock(&lirc_dev_lock); + if (!ir) { retval = -ENODEV; goto error; @@ -476,8 +478,6 @@ int lirc_dev_fop_open(struct inode *inode, struct file *file) } error: - mutex_unlock(&lirc_dev_lock); - nonseekable_open(inode, file); return retval; -- cgit