• Marek Szyprowski's avatar
    ASoC: max98090: fix lockdep warning · 2dc98af6
    Marek Szyprowski authored
    Commit 62d5ae4c ("ASoC: max98090: save and restore SHDN when changing
    sensitive registers") extended the code for handling many controls by
    adding a custom put function to them. That new custom put function
    properly handles relations between codec's hardware registers. However
    they used card->dapm_mutex to properly serialize those operations. This
    in turn triggers a lockdep warning about possible circular dependency.
    Fix this by introducing a separate mutex only for serializing the SHDN
    hardware register related operations.
    
    This fixes the following lockdep warning observed on Exynos4412-based
    Odroid U3 board:
    ======================================================
    WARNING: possible circular locking dependency detected
    5.5.0-rc5-next-20200107 #166 Not tainted
    ------------------------------------------------------
    alsactl/1104 is trying to acquire lock:
    ed0d50f4 (&card->dapm_mutex){+.+.}, at: max98090_shdn_save+0x1c/0x28
    
    but task is already holding lock:
    edb4b49c (&card->controls_rwsem){++++}, at: snd_ctl_ioctl+0xcc/0xbb8
    
    which lock already depends on the new lock.
    
    the existing dependency chain (in reverse order) is:
    
    -> #1 (&card->controls_rwsem){++++}:
           snd_ctl_add_replace+0x3c/0x84
           dapm_create_or_share_kcontrol+0x24c/0x2e0
           snd_soc_dapm_new_widgets+0x308/0x594
           snd_soc_bind_card+0x80c/0xad4
           devm_snd_soc_register_card+0x34/0x6c
           odroid_audio_probe+0x288/0x34c
           platform_drv_probe+0x6c/0xa4
           really_probe+0x200/0x490
           driver_probe_device+0x78/0x1f8
           bus_for_each_drv+0x74/0xb8
           __device_attach+0xd4/0x16c
           bus_probe_device+0x88/0x90
           deferred_probe_work_func+0x3c/0xd0
           process_one_work+0x22c/0x7c4
           worker_thread+0x44/0x524
           kthread+0x130/0x164
           ret_from_fork+0x14/0x20
           0x0
    
    -> #0 (&card->dapm_mutex){+.+.}:
           lock_acquire+0xe8/0x270
           __mutex_lock+0x9c/0xb18
           mutex_lock_nested+0x1c/0x24
           max98090_shdn_save+0x1c/0x28
           max98090_put_enum_double+0x20/0x40
           snd_ctl_ioctl+0x190/0xbb8
           ksys_ioctl+0x470/0xaf8
           ret_fast_syscall+0x0/0x28
           0xbefaa564
    
    other info that might help us debug this:
    
     Possible unsafe locking scenario:
    
           CPU0                    CPU1
           ----                    ----
      lock(&card->controls_rwsem);
                                   lock(&card->dapm_mutex);
                                   lock(&card->controls_rwsem);
      lock(&card->dapm_mutex);
    
     *** DEADLOCK ***
    
    1 lock held by alsactl/1104:
     #0: edb4b49c (&card->controls_rwsem){++++}, at: snd_ctl_ioctl+0xcc/0xbb8
    
    stack backtrace:
    CPU: 0 PID: 1104 Comm: alsactl Not tainted 5.5.0-rc5-next-20200107 #166
    Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
    (unwind_backtrace) from [<c010e180>] (show_stack+0x10/0x14)
    (show_stack) from [<c0b2a09c>] (dump_stack+0xb4/0xe0)
    (dump_stack) from [<c018a1c0>] (check_noncircular+0x1ec/0x208)
    (check_noncircular) from [<c018c5dc>] (__lock_acquire+0x1210/0x25ec)
    (__lock_acquire) from [<c018e2d8>] (lock_acquire+0xe8/0x270)
    (lock_acquire) from [<c0b49678>] (__mutex_lock+0x9c/0xb18)
    (__mutex_lock) from [<c0b4a110>] (mutex_lock_nested+0x1c/0x24)
    (mutex_lock_nested) from [<c0839b3c>] (max98090_shdn_save+0x1c/0x28)
    (max98090_shdn_save) from [<c083a5b8>] (max98090_put_enum_double+0x20/0x40)
    (max98090_put_enum_double) from [<c080d0e8>] (snd_ctl_ioctl+0x190/0xbb8)
    (snd_ctl_ioctl) from [<c02cafec>] (ksys_ioctl+0x470/0xaf8)
    (ksys_ioctl) from [<c0101000>] (ret_fast_syscall+0x0/0x28)
    ...
    
    Fixes: 62d5ae4c ("ASoC: max98090: save and restore SHDN when changing sensitive registers")
    Signed-off-by: default avatarMarek Szyprowski <m.szyprowski@samsung.com>
    Link: https://lore.kernel.org/r/20200108115007.31095-2-m.szyprowski@samsung.comSigned-off-by: default avatarMark Brown <broonie@kernel.org>
    2dc98af6
max98090.c 90.8 KB