From 033919e0f8debfc2e5cfb13edf8fbdeff5b47b7d Mon Sep 17 00:00:00 2001 From: Heiner Kallweit Date: Sun, 31 Jul 2016 08:56:15 -0300 Subject: [PATCH] [media] media: rc: fix deadlock when module ir_lirc_codec is removed When removing module ir_lirc_codec I got this deadlock warning. Fix this by introducing a separate mutex to protect access to available_protocols instead of using ir_raw_handler_lock for this purpose. ====================================================== [ INFO: possible circular locking dependency detected ] 4.7.0-next-20160729 #1 Not tainted ------------------------------------------------------- rmmod/2542 is trying to acquire lock: (&dev->lock){+.+.+.}, at: [] ir_raw_handler_unregister+0x77/0xd0 [rc_core] but task is already holding lock: (ir_raw_handler_lock){+.+.+.}, at: [] ir_raw_handler_unregister+0x22/0xd0 [rc_core] which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (ir_raw_handler_lock){+.+.+.}: [] lock_acquire+0xb2/0x1e0 [] mutex_lock_nested+0x5f/0x360 [] ir_raw_get_allowed_protocols+0x13/0x30 [rc_core] [] store_protocols+0x2fa/0x480 [rc_core] [] dev_attr_store+0x13/0x20 [] sysfs_kf_write+0x40/0x50 [] kernfs_fop_write+0x150/0x1e0 [] __vfs_write+0x23/0x120 [] vfs_write+0xb0/0x190 [] SyS_write+0x44/0xa0 [] entry_SYSCALL_64_fastpath+0x18/0xa8 -> #0 (&dev->lock){+.+.+.}: [] __lock_acquire+0x10fc/0x1270 [] lock_acquire+0xb2/0x1e0 [] mutex_lock_nested+0x5f/0x360 [] ir_raw_handler_unregister+0x77/0xd0 [rc_core] [] ir_lirc_codec_exit+0x10/0x12 [ir_lirc_codec] [] SyS_delete_module+0x168/0x220 [] entry_SYSCALL_64_fastpath+0x18/0xa8 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(ir_raw_handler_lock); lock(&dev->lock); lock(ir_raw_handler_lock); lock(&dev->lock); *** DEADLOCK *** 1 lock held by rmmod/2542: #0: (ir_raw_handler_lock){+.+.+.}, at: [] ir_raw_handler_unregister+0x22/0xd0 [rc_core] stack backtrace: CPU: 0 PID: 2542 Comm: rmmod Not tainted 4.7.0-next-20160729 #1 Hardware name: ZOTAC ZBOX-CI321NANO/ZBOX-CI321NANO, BIOS B246P105 06/01/2015 0000000000000000 ffff88006e607cc0 ffffffff812715f5 ffffffff8232b230 ffffffff8232b230 ffff88006e607d00 ffffffff810a846e 00000000790107f0 ffff880079010818 ffff8800790107f0 1efeb9f4f0dd2e6f ffff880079010000 Call Trace: [] dump_stack+0x68/0x93 [] print_circular_bug+0x1be/0x210 [] __lock_acquire+0x10fc/0x1270 [] ? debug_lockdep_rcu_enabled+0x1d/0x20 [] lock_acquire+0xb2/0x1e0 [] ? ir_raw_handler_unregister+0x77/0xd0 [rc_core] [] mutex_lock_nested+0x5f/0x360 [] ? ir_raw_handler_unregister+0x77/0xd0 [rc_core] [] ? trace_hardirqs_on_caller+0xee/0x1b0 [] ir_raw_handler_unregister+0x77/0xd0 [rc_core] [] ir_lirc_codec_exit+0x10/0x12 [ir_lirc_codec] [] SyS_delete_module+0x168/0x220 [] entry_SYSCALL_64_fastpath+0x18/0xa8 Signed-off-by: Heiner Kallweit Signed-off-by: Mauro Carvalho Chehab --- drivers/media/rc/rc-ir-raw.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/media/rc/rc-ir-raw.c b/drivers/media/rc/rc-ir-raw.c index 144304c94606..205ecc602e34 100644 --- a/drivers/media/rc/rc-ir-raw.c +++ b/drivers/media/rc/rc-ir-raw.c @@ -26,6 +26,7 @@ static LIST_HEAD(ir_raw_client_list); /* Used to handle IR raw handler extensions */ static DEFINE_MUTEX(ir_raw_handler_lock); static LIST_HEAD(ir_raw_handler_list); +static DEFINE_MUTEX(available_protocols_lock); static u64 available_protocols; static int ir_raw_event_thread(void *data) @@ -234,9 +235,9 @@ u64 ir_raw_get_allowed_protocols(void) { u64 protocols; - mutex_lock(&ir_raw_handler_lock); + mutex_lock(&available_protocols_lock); protocols = available_protocols; - mutex_unlock(&ir_raw_handler_lock); + mutex_unlock(&available_protocols_lock); return protocols; } @@ -330,7 +331,9 @@ int ir_raw_handler_register(struct ir_raw_handler *ir_raw_handler) if (ir_raw_handler->raw_register) list_for_each_entry(raw, &ir_raw_client_list, list) ir_raw_handler->raw_register(raw->dev); + mutex_lock(&available_protocols_lock); available_protocols |= ir_raw_handler->protocols; + mutex_unlock(&available_protocols_lock); mutex_unlock(&ir_raw_handler_lock); return 0; @@ -349,7 +352,9 @@ void ir_raw_handler_unregister(struct ir_raw_handler *ir_raw_handler) if (ir_raw_handler->raw_unregister) ir_raw_handler->raw_unregister(raw->dev); } + mutex_lock(&available_protocols_lock); available_protocols &= ~protocols; + mutex_unlock(&available_protocols_lock); mutex_unlock(&ir_raw_handler_lock); } EXPORT_SYMBOL(ir_raw_handler_unregister); -- 2.20.1