[alsa-devel] sound/core/timer: Deadlock on register_mutex

[Kirill A. Shutemov]

On Wed, Oct 30, 2019 at 04:04:01PM +0100, Takashi Iwai wrote:
> On Wed, 30 Oct 2019 15:10:29 +0100,
> Kirill A. Shutemov wrote:
> > 
> > Hi,
> > 
> > I've stepped on this after pulling USB sound card:
> > 
> > 	 ============================================
> > 	 WARNING: possible recursive locking detected
> > 	 5.4.0-rc4-00090-g95b5dc072cc3-dirty #48 Not tainted
> > 	 --------------------------------------------
> > 	 xdg-screensaver/1321 is trying to acquire lock:
> > 	 ffffffffbaf6b3a0 (register_mutex){+.+.}, at: snd_timer_free.part.0 (/include/linux/compiler.h:199 /include/linux/list.h:268 /sound/core/timer.c:944)
> > 
> > 	but task is already holding lock:
> > 	 ffffffffbaf6b3a0 (register_mutex){+.+.}, at: snd_timer_close (/sound/core/timer.c:416)
> > 
> > 	other info that might help us debug this:
> > 	  Possible unsafe locking scenario:
> > 
> > 		CPU0
> > 		----
> > 	   lock(register_mutex);
> > 	   lock(register_mutex);
> > 
> > 	*** DEADLOCK ***
> > 
> > 	  May be due to missing lock nesting notation
> > 
> > 	 2 locks held by xdg-screensaver/1321:
> > 	 #0: ffff9f74bbf5ef50 (&tu->ioctl_lock){+.+.}, at: snd_timer_user_release (/sound/core/timer.c:1467)
> > 	 #1: ffffffffbaf6b3a0 (register_mutex){+.+.}, at: snd_timer_close (/sound/core/timer.c:416)
> > 
> > 	stack backtrace:
> > 	 CPU: 27 PID: 1321 Comm: xdg-screensaver Not tainted 5.4.0-rc4-00090-g95b5dc072cc3-dirty #48
> > 	 Hardware name: Gigabyte Technology Co., Ltd. X299 AORUS Gaming 3 Pro/X299 AORUS Gaming 3 Pro-CF, BIOS F3 12/28/2017
> > 	 Call Trace:
> > 	 dump_stack (/lib/dump_stack.c:115)
> > 	 __lock_acquire.cold (/kernel/locking/lockdep.c:2371 /kernel/locking/lockdep.c:2412 /kernel/locking/lockdep.c:2955 /kernel/locking/lockdep.c:3955)
> > 	 ? __lock_acquire (/kernel/locking/lockdep.c:3962)
> > 	 lock_acquire (/arch/x86/include/asm/current.h:15 /kernel/locking/lockdep.c:4489)
> > 	 ? snd_timer_free.part.0 (/include/linux/compiler.h:199 /include/linux/list.h:268 /sound/core/timer.c:944)
> > 	 __mutex_lock (/include/linux/compiler.h:199 /arch/x86/include/asm/atomic64_64.h:22 /include/asm-generic/atomic-instrumented.h:837 /include/asm-generic/atomic-long.h:28 /kernel/locking/mutex.c:111 /kernel/locking/mutex.c:152 /kernel/locking/mutex.c:958 /kernel/locking/mutex.c:1103)
> > 	 ? snd_timer_free.part.0 (/include/linux/compiler.h:199 /include/linux/list.h:268 /sound/core/timer.c:944)
> > 	 ? __mutex_lock (/include/linux/compiler.h:199 /arch/x86/include/asm/atomic64_64.h:22 /include/asm-generic/atomic-instrumented.h:837 /include/asm-generic/atomic-long.h:28 /kernel/locking/mutex.c:111 /kernel/locking/mutex.c:152 /kernel/locking/mutex.c:958 /kernel/locking/mutex.c:1103)
> > 	 ? __mutex_lock (/arch/x86/include/asm/preempt.h:102 /kernel/locking/mutex.c:964 /kernel/locking/mutex.c:1103)
> > 	 ? snd_timer_free.part.0 (/include/linux/compiler.h:199 /include/linux/list.h:268 /sound/core/timer.c:944)
> > 	 ? snd_timer_free.part.0 (/include/linux/compiler.h:199 /include/linux/list.h:268 /sound/core/timer.c:944)
> > 	 ? lockdep_hardirqs_on (/kernel/locking/lockdep.c:3394 /kernel/locking/lockdep.c:3434)
> > 	 snd_timer_free.part.0 (/include/linux/compiler.h:199 /include/linux/list.h:268 /sound/core/timer.c:944)
> > 	 snd_timer_dev_free (/sound/core/timer.c:967)
> > 	 __snd_device_free (/sound/core/device.c:76)
> > 	 snd_device_free_all (/sound/core/device.c:228)
> > 	 release_card_device (/sound/core/init.c:471 /sound/core/init.c:140)
> > 	 device_release (/drivers/base/core.c:1105)
> > 	 kobject_put (/lib/kobject.c:697 /lib/kobject.c:722 /include/linux/kref.h:65 /lib/kobject.c:739)
> > 	 snd_timer_close_locked (/sound/core/timer.c:398)
> > 	 snd_timer_close (/sound/core/timer.c:417)
> > 	 snd_timer_user_release (/sound/core/timer.c:1469)
> > 	 __fput (/fs/file_table.c:281)
> > 	 task_work_run (/kernel/task_work.c:115 (discriminator 1))
> > 	 exit_to_usermode_loop (/include/linux/tracehook.h:188 /arch/x86/entry/common.c:163)
> > 	 do_syscall_64 (/arch/x86/entry/common.c:194 /arch/x86/entry/common.c:274 /arch/x86/entry/common.c:300)
> > 	 entry_SYSCALL_64_after_hwframe (/arch/x86/entry/entry_64.S:177)
> 
> OK, this looks like a deadlock that is via put_device() called at
> closing the timer device that is the last open instance while freeing
> the card.
> 
> Could you try the patch below?

I can, but I'm not sure if I can trigger the issue for the second time.

-- 
 Kirill A. Shutemov