[alsa-devel] sound/core/timer: Deadlock on register_mutex
Takashi Iwai
tiwai at suse.de
Wed Oct 30 16:04:01 CET 2019
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?
thanks,
Takashi
--- a/sound/core/timer.c
+++ b/sound/core/timer.c
@@ -226,7 +226,8 @@ static int snd_timer_check_master(struct snd_timer_instance *master)
return 0;
}
-static int snd_timer_close_locked(struct snd_timer_instance *timeri);
+static int snd_timer_close_locked(struct snd_timer_instance *timeri,
+ struct device **card_dev_to_put);
/*
* open a timer instance
@@ -238,6 +239,7 @@ int snd_timer_open(struct snd_timer_instance **ti,
{
struct snd_timer *timer;
struct snd_timer_instance *timeri = NULL;
+ struct device *card_dev_to_put = NULL;
int err;
mutex_lock(®ister_mutex);
@@ -261,7 +263,7 @@ int snd_timer_open(struct snd_timer_instance **ti,
list_add_tail(&timeri->open_list, &snd_timer_slave_list);
err = snd_timer_check_slave(timeri);
if (err < 0) {
- snd_timer_close_locked(timeri);
+ snd_timer_close_locked(timeri, &card_dev_to_put);
timeri = NULL;
}
goto unlock;
@@ -313,7 +315,7 @@ int snd_timer_open(struct snd_timer_instance **ti,
timeri = NULL;
if (timer->card)
- put_device(&timer->card->card_dev);
+ card_dev_to_put = &timer->card->card_dev;
module_put(timer->module);
goto unlock;
}
@@ -323,12 +325,15 @@ int snd_timer_open(struct snd_timer_instance **ti,
timer->num_instances++;
err = snd_timer_check_master(timeri);
if (err < 0) {
- snd_timer_close_locked(timeri);
+ snd_timer_close_locked(timeri, &card_dev_to_put);
timeri = NULL;
}
unlock:
mutex_unlock(®ister_mutex);
+ /* put_device() is called after unlock for avoiding deadlock */
+ if (card_dev_to_put)
+ put_device(card_dev_to_put);
*ti = timeri;
return err;
}
@@ -338,11 +343,13 @@ EXPORT_SYMBOL(snd_timer_open);
* close a timer instance
* call this with register_mutex down.
*/
-static int snd_timer_close_locked(struct snd_timer_instance *timeri)
+static int snd_timer_close_locked(struct snd_timer_instance *timeri,
+ struct device **card_devp_to_put)
{
struct snd_timer *timer = timeri->timer;
struct snd_timer_instance *slave, *tmp;
+ *card_devp_to_put = NULL;
if (timer) {
spin_lock_irq(&timer->lock);
timeri->flags |= SNDRV_TIMER_IFLG_DEAD;
@@ -395,7 +402,7 @@ static int snd_timer_close_locked(struct snd_timer_instance *timeri)
timer->hw.close(timer);
/* release a card refcount for safe disconnection */
if (timer->card)
- put_device(&timer->card->card_dev);
+ *card_devp_to_put = &timer->card->card_dev;
module_put(timer->module);
}
@@ -407,14 +414,18 @@ static int snd_timer_close_locked(struct snd_timer_instance *timeri)
*/
int snd_timer_close(struct snd_timer_instance *timeri)
{
+ struct device *card_dev_to_put = NULL;
int err;
if (snd_BUG_ON(!timeri))
return -ENXIO;
mutex_lock(®ister_mutex);
- err = snd_timer_close_locked(timeri);
+ err = snd_timer_close_locked(timeri, &card_dev_to_put);
mutex_unlock(®ister_mutex);
+ /* put_device() is called after unlock for avoiding deadlock */
+ if (card_dev_to_put)
+ put_device(card_dev_to_put);
return err;
}
EXPORT_SYMBOL(snd_timer_close);
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