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Date: Tue, 25 Aug 2015 23:15:23 +0600
From: Alexnader Kuleshov <kuleshovmail@...il.com>
To: Takashi Iwai <tiwai@...e.de>
Cc: Alexnader Kuleshov <kuleshovmail@...il.com>,
Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
linux-kernel@...r.kernel.org
Subject: Re: ALSA/usb-audio: snd_usb_autoresume possible recursive locking
detected
Hello Takashi, just tested it on my linux box against 4.2.0-rc8+ and there is
the same 'possible recursive locking detected', but another:
[ 13.422080] =============================================
[ 13.422081] [ INFO: possible recursive locking detected ]
[ 13.422082] 4.2.0-rc8+ #61 Not tainted
[ 13.422083] ---------------------------------------------
[ 13.422084] systemd-udevd/533 is trying to acquire lock:
[ 13.422085] (&chip->shutdown_rwsem){.+.+.+}, at: [<ffffffffa0253da3>] snd_usb_autoresume+0x1d/0x52 [snd_usb_audio]
[ 13.422094]
but task is already holding lock:
[ 13.422094] (&chip->shutdown_rwsem){.+.+.+}, at: [<ffffffffa0257377>] snd_usb_mixer_set_ctl_value+0xd0/0x1ad [snd_usb_audio]
[ 13.422100]
other info that might help us debug this:
[ 13.422101] Possible unsafe locking scenario:
[ 13.422102] CPU0
[ 13.422102] ----
[ 13.422103] lock(&chip->shutdown_rwsem);
[ 13.422104] lock(&chip->shutdown_rwsem);
[ 13.422105]
*** DEADLOCK ***
[ 13.422106] May be due to missing lock nesting notation
[ 13.422107] 4 locks held by systemd-udevd/533:
[ 13.422108] #0: (&dev->mutex){......}, at: [<ffffffff813b3414>] __driver_attach+0x30/0x80
[ 13.422112] #1: (&dev->mutex){......}, at: [<ffffffff813b342c>] __driver_attach+0x48/0x80
[ 13.422115] #2: (register_mutex#4){+.+.+.}, at: [<ffffffffa0253670>] usb_audio_probe+0xa3/0x7b9 [snd_usb_audio]
[ 13.422120] #3: (&chip->shutdown_rwsem){.+.+.+}, at: [<ffffffffa0257377>] snd_usb_mixer_set_ctl_value+0xd0/0x1ad [snd_usb_audio]
[ 13.422125]
stack backtrace:
[ 13.422127] CPU: 7 PID: 533 Comm: systemd-udevd Not tainted 4.2.0-rc8+ #61
[ 13.422128] Hardware name: Gigabyte Technology Co., Ltd. Z97X-UD5H-BK/Z97X-UD5H-BK, BIOS F6 06/17/2014
[ 13.422129] 0000000000000000 0000000071d6ca78 ffff880407bf7538 ffffffff815ba622
[ 13.422131] 0000000000000000 ffffffff8239a680 ffff880407bf75f8 ffffffff810dd54e
[ 13.422133] ffff880409db64a8 ffffffff00000000 0000000182000201 ffffffff8239a680
[ 13.422135] Call Trace:
[ 13.422137] [<ffffffff815ba622>] dump_stack+0x4c/0x65
[ 13.422140] [<ffffffff810dd54e>] validate_chain.isra.9+0x75d/0xf59
[ 13.422142] [<ffffffff810de69c>] ? mark_held_locks+0x5f/0x76
[ 13.422144] [<ffffffff810e0964>] __lock_acquire+0x753/0xabf
[ 13.422146] [<ffffffff810e1131>] lock_acquire+0x7b/0x9c
[ 13.422151] [<ffffffffa0253da3>] ? snd_usb_autoresume+0x1d/0x52 [snd_usb_audio]
[ 13.422153] [<ffffffff815c4896>] down_read+0x44/0x8d
[ 13.422156] [<ffffffffa0253da3>] ? snd_usb_autoresume+0x1d/0x52 [snd_usb_audio]
[ 13.422160] [<ffffffffa0253da3>] snd_usb_autoresume+0x1d/0x52 [snd_usb_audio]
[ 13.422162] [<ffffffff815c48d6>] ? down_read+0x84/0x8d
[ 13.422167] [<ffffffffa025738c>] snd_usb_mixer_set_ctl_value+0xe5/0x1ad [snd_usb_audio]
[ 13.422171] [<ffffffffa025784a>] get_min_max_with_quirks+0x155/0x5e4 [snd_usb_audio]
[ 13.422176] [<ffffffffa02581c1>] build_feature_ctl+0x33a/0x419 [snd_usb_audio]
[ 13.422181] [<ffffffffa02586f9>] parse_audio_unit+0x459/0xa03 [snd_usb_audio]
[ 13.422186] [<ffffffffa02590f4>] snd_usb_mixer_controls+0xe8/0x169 [snd_usb_audio]
[ 13.422190] [<ffffffffa02593b4>] snd_usb_create_mixer+0xb4/0x261 [snd_usb_audio]
[ 13.422194] [<ffffffffa02535ba>] ? snd_usb_create_stream+0x151/0x164 [snd_usb_audio]
[ 13.422197] [<ffffffffa0253ccd>] usb_audio_probe+0x700/0x7b9 [snd_usb_audio]
[ 13.422199] [<ffffffff81413bb7>] usb_probe_interface+0x139/0x1c3
[ 13.422201] [<ffffffff813b329a>] driver_probe_device+0xd0/0x21a
[ 13.422203] [<ffffffff813b3441>] __driver_attach+0x5d/0x80
[ 13.422205] [<ffffffff813b33e4>] ? driver_probe_device+0x21a/0x21a
[ 13.422207] [<ffffffff813b1850>] bus_for_each_dev+0x77/0xa5
[ 13.422210] [<ffffffff813b2f94>] driver_attach+0x19/0x1b
[ 13.422212] [<ffffffff813b2a87>] bus_add_driver+0xe8/0x1da
[ 13.422213] [<ffffffff813b3a26>] driver_register+0x86/0xc3
[ 13.422215] [<ffffffff81412b6c>] usb_register_driver+0xa8/0x146
[ 13.422216] [<ffffffffa0345000>] ? 0xffffffffa0345000
[ 13.422220] [<ffffffffa034501e>] usb_audio_driver_init+0x1e/0x20 [snd_usb_audio]
[ 13.422222] [<ffffffff81000380>] do_one_initcall+0x17f/0x194
[ 13.422225] [<ffffffff810c31cd>] ? __might_sleep+0x71/0x79
[ 13.422228] [<ffffffff815b96ad>] do_init_module+0x56/0x1d7
[ 13.422230] [<ffffffff81109a8b>] load_module+0x17f5/0x1c1e
[ 13.422234] [<ffffffff8117994b>] ? kernel_read+0x4b/0x6d
[ 13.422236] [<ffffffff8110a066>] SyS_finit_module+0x6f/0x90
[ 13.422239] [<ffffffff815c6a57>] entry_SYSCALL_64_fastpath+0x12/0x6f
Thank you.
On 08-25-15, Takashi Iwai wrote:
>
> Could you try the patch below?
>
>
> Takashi
>
> -- 8< --
> From: Takashi Iwai <tiwai@...e.de>
> Subject: [PATCH] ALSA: usb-audio: Avoid nested autoresume calls
>
> Since snd_usb_autoresume() invokes down_read() to shutdown_rwsem, this
> triggers lockdep warnings like
> =============================================
> [ INFO: possible recursive locking detected ]
> 4.2.0-rc8+ #61 Not tainted
> ---------------------------------------------
> pulseaudio/980 is trying to acquire lock:
> (&chip->shutdown_rwsem){.+.+.+}, at: [<ffffffffa0355dac>] snd_usb_autoresume+0x1d/0x52 [snd_usb_audio]
> but task is already holding lock:
> (&chip->shutdown_rwsem){.+.+.+}, at: [<ffffffffa0355dac>] snd_usb_autoresume+0x1d/0x52 [snd_usb_audio]
>
> One could avoid this with down_read_nested(). But a quicker solution
> is just to skip snd_usb_autoresume() call and relevant down_read()
> inside the resume path. This is already marked via chip->in_pm flag,
> so we can check it easily.
>
> This patch adds the workaround in the regular resume path (via
> snd_usb_mixer_set_ctl_value()). A more comprehensive coverage to all
> resume paths will follow later.
>
> Reported-by: Alexnader Kuleshov <kuleshovmail@...il.com>
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Takashi Iwai <tiwai@...e.de>
> ---
> sound/usb/mixer.c | 21 +++++++++++++++------
> 1 file changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
> index c50790cb3f4d..dd9caac4998a 100644
> --- a/sound/usb/mixer.c
> +++ b/sound/usb/mixer.c
> @@ -463,6 +463,7 @@ int snd_usb_mixer_set_ctl_value(struct usb_mixer_elem_info *cval,
> struct snd_usb_audio *chip = cval->head.mixer->chip;
> unsigned char buf[4];
> int idx = 0, val_len, err, timeout = 10;
> + bool autoresume;
>
> validx += cval->idx_off;
>
> @@ -485,10 +486,16 @@ int snd_usb_mixer_set_ctl_value(struct usb_mixer_elem_info *cval,
> buf[1] = (value_set >> 8) & 0xff;
> buf[2] = (value_set >> 16) & 0xff;
> buf[3] = (value_set >> 24) & 0xff;
> - err = snd_usb_autoresume(chip);
> - if (err < 0)
> - return -EIO;
> - down_read(&chip->shutdown_rwsem);
> +
> + /* do autoresume and lock only when invoked from non-resume path */
> + autoresume = !chip->in_pm;
> + if (autoresume) {
> + err = snd_usb_autoresume(chip);
> + if (err < 0)
> + return -EIO;
> + down_read(&chip->shutdown_rwsem);
> + }
> +
> while (timeout-- > 0) {
> if (chip->shutdown)
> break;
> @@ -506,8 +513,10 @@ int snd_usb_mixer_set_ctl_value(struct usb_mixer_elem_info *cval,
> err = -EINVAL;
>
> out:
> - up_read(&chip->shutdown_rwsem);
> - snd_usb_autosuspend(chip);
> + if (autoresume) {
> + up_read(&chip->shutdown_rwsem);
> + snd_usb_autosuspend(chip);
> + }
> return err;
> }
>
> --
> 2.5.0
>
--
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