Re: ALSA/usb-audio: snd_usb_autoresume possible recursive locking detected
From: Takashi Iwai
Date: Tue Aug 25 2015 - 10:51:23 EST
On Tue, 25 Aug 2015 15:48:58 +0200,
Takashi Iwai wrote:
>
> On Tue, 25 Aug 2015 15:32:56 +0200,
> Alexnader Kuleshov wrote:
> >
> > Hello all,
> >
> > Today I've update to 4.2.0-rc8+ and started to get following lines in the
> > dmesg output:
> >
> > [ 13.884092] =============================================
> > [ 13.884092] [ INFO: possible recursive locking detected ]
> > [ 13.884094] 4.2.0-rc8+ #61 Not tainted
> > [ 13.884094] ---------------------------------------------
> > [ 13.884095] pulseaudio/980 is trying to acquire lock:
> > [ 13.884096] (&chip->shutdown_rwsem){.+.+.+}, at: [<ffffffffa0355dac>] snd_usb_autoresume+0x1d/0x52 [snd_usb_audio]
> > [ 13.884103]
> > but task is already holding lock:
> > [ 13.884104] (&chip->shutdown_rwsem){.+.+.+}, at: [<ffffffffa0355dac>] snd_usb_autoresume+0x1d/0x52 [snd_usb_audio]
> > [ 13.884107]
> > other info that might help us debug this:
> > [ 13.884108] Possible unsafe locking scenario:
> >
> > [ 13.884109] CPU0
> > [ 13.884110] ----
> > [ 13.884110] lock(&chip->shutdown_rwsem);
> > [ 13.884111] lock(&chip->shutdown_rwsem);
> > [ 13.884112]
> > *** DEADLOCK ***
> >
> > [ 13.884113] May be due to missing lock nesting notation
> >
> > [ 13.884114] 2 locks held by pulseaudio/980:
> > [ 13.884115] #0: (&pcm->open_mutex){+.+.+.}, at: [<ffffffffa02ac9bc>] snd_pcm_open+0xa9/0x1f8 [snd_pcm]
> > [ 13.884120] #1: (&chip->shutdown_rwsem){.+.+.+}, at: [<ffffffffa0355dac>] snd_usb_autoresume+0x1d/0x52 [snd_usb_audio]
> > [ 13.884124]
> > stack backtrace:
> > [ 13.884125] CPU: 0 PID: 980 Comm: pulseaudio Not tainted 4.2.0-rc8+ #61
> > [ 13.884126] Hardware name: Gigabyte Technology Co., Ltd. Z97X-UD5H-BK/Z97X-UD5H-BK, BIOS F6 06/17/2014
> > [ 13.884127] 0000000000000000 000000003d4c66e6 ffff88040897b4d8 ffffffff815ba622
> > [ 13.884129] 0000000000000000 ffffffff82399320 ffff88040897b598 ffffffff810dd54e
> > [ 13.884130] ffff88040ac486a8 0000000000000000 0000000000000001 ffffffff82399320
> > [ 13.884132] Call Trace:
> > [ 13.884134] [<ffffffff815ba622>] dump_stack+0x4c/0x65
> > [ 13.884137] [<ffffffff810dd54e>] validate_chain.isra.9+0x75d/0xf59
> > [ 13.884139] [<ffffffff815c62b3>] ? _raw_spin_unlock_irq+0x28/0x34
> > [ 13.884140] [<ffffffff810e0964>] __lock_acquire+0x753/0xabf
> > [ 13.884142] [<ffffffff81163819>] ? kfree+0xb8/0x10d
> > [ 13.884143] [<ffffffff810e1131>] lock_acquire+0x7b/0x9c
> > [ 13.884146] [<ffffffffa0355dac>] ? snd_usb_autoresume+0x1d/0x52 [snd_usb_audio]
> > [ 13.884147] [<ffffffff815c4896>] down_read+0x44/0x8d
> > [ 13.884150] [<ffffffffa0355dac>] ? snd_usb_autoresume+0x1d/0x52 [snd_usb_audio]
> > [ 13.884152] [<ffffffffa0355dac>] snd_usb_autoresume+0x1d/0x52 [snd_usb_audio]
> > [ 13.884153] [<ffffffff815c37e5>] ? __mutex_unlock_slowpath+0x110/0x11b
> > [ 13.884156] [<ffffffffa0359338>] snd_usb_mixer_set_ctl_value+0x9a/0x16d [snd_usb_audio]
> > [ 13.884159] [<ffffffffa035957e>] snd_usb_set_cur_mix_value+0x4d/0x77 [snd_usb_audio]
> > [ 13.884161] [<ffffffffa0359db9>] restore_mixer_value+0x74/0x87 [snd_usb_audio]
> > [ 13.884164] [<ffffffffa035b581>] snd_usb_mixer_resume+0x64/0x70 [snd_usb_audio]
> > [ 13.884166] [<ffffffffa035505c>] __usb_audio_resume+0x5c/0xd8 [snd_usb_audio]
> > [ 13.884169] [<ffffffff81413ca4>] ? usb_runtime_suspend+0x63/0x63
> > [ 13.884171] [<ffffffffa03550e6>] usb_audio_reset_resume+0xe/0x10 [snd_usb_audio]
> > [ 13.884172] [<ffffffff81412fde>] usb_resume_interface.isra.1+0x6c/0xbd
> > [ 13.884174] [<ffffffff814130cf>] usb_resume_both+0xa0/0xc0
> > [ 13.884175] [<ffffffff81413cb9>] usb_runtime_resume+0x15/0x17
> > [ 13.884178] [<ffffffff813b92b0>] __rpm_callback+0x35/0x5d
> > [ 13.884179] [<ffffffff81413ca4>] ? usb_runtime_suspend+0x63/0x63
> > [ 13.884180] [<ffffffff813b9330>] rpm_callback+0x58/0x77
> > [ 13.884182] [<ffffffff81413ca4>] ? usb_runtime_suspend+0x63/0x63
> > [ 13.884183] [<ffffffff813ba0db>] rpm_resume+0x370/0x412
> > [ 13.884184] [<ffffffff813ba06c>] rpm_resume+0x301/0x412
> > [ 13.884186] [<ffffffff813ba1e3>] __pm_runtime_resume+0x66/0x82
> > [ 13.884187] [<ffffffff81412e10>] usb_autopm_get_interface+0x1e/0x48
> > [ 13.884190] [<ffffffffa0355dcc>] snd_usb_autoresume+0x3d/0x52 [snd_usb_audio]
> > [ 13.884191] [<ffffffff810d84b9>] ? __init_waitqueue_head+0x37/0x4b
> > [ 13.884194] [<ffffffffa035e765>] snd_usb_pcm_open+0x181/0x3bb [snd_usb_audio]
> > [ 13.884197] [<ffffffffa035e9ad>] snd_usb_capture_open+0xe/0x10 [snd_usb_audio]
> > [ 13.884200] [<ffffffffa02ac8c6>] snd_pcm_open_substream+0x50/0x9d [snd_pcm]
> > [ 13.884203] [<ffffffffa02ac9ce>] snd_pcm_open+0xbb/0x1f8 [snd_pcm]
> > [ 13.884204] [<ffffffff810de87d>] ? trace_hardirqs_on+0xd/0xf
> > [ 13.884206] [<ffffffff810c5550>] ? wake_up_q+0x53/0x53
> > [ 13.884209] [<ffffffffa02acb49>] snd_pcm_capture_open+0x3e/0x61 [snd_pcm]
> > [ 13.884212] [<ffffffffa028232d>] snd_open+0x130/0x13f [snd]
> > [ 13.884214] [<ffffffff811788c5>] chrdev_open+0x13b/0x175
> > [ 13.884215] [<ffffffff8117878a>] ? cdev_put+0x20/0x20
> > [ 13.884217] [<ffffffff81172f31>] do_dentry_open.isra.1+0x1d2/0x2c9
> > [ 13.884218] [<ffffffff8117d0e4>] ? __inode_permission+0x84/0x95
> > [ 13.884219] [<ffffffff81173bf6>] vfs_open+0x50/0x54
> > [ 13.884221] [<ffffffff811815e0>] path_openat+0xa90/0xd0f
> > [ 13.884222] [<ffffffff810e0900>] ? __lock_acquire+0x6ef/0xabf
> > [ 13.884223] [<ffffffff8118269e>] do_filp_open+0x48/0xac
> > [ 13.884225] [<ffffffff815c6203>] ? _raw_spin_unlock+0x23/0x2e
> > [ 13.884227] [<ffffffff8118f5b7>] ? __alloc_fd+0x144/0x156
> > [ 13.884228] [<ffffffff81173f3a>] do_sys_open+0x154/0x1f7
> > [ 13.884229] [<ffffffff81173ff6>] SyS_open+0x19/0x1b
> > [ 13.884231] [<ffffffff815c6a57>] entry_SYSCALL_64_fastpath+0x12/0x6f
> >
> > Previous version of the kernel was 4.2.0-rc6+.
>
> This should be a false positive warning, a side-effect now by fix of
> runtime PM. That is, it proves that the runtime PM is activated.
> I'll consider to reduce this later.
Could you try the patch below?
Takashi
-- 8< --
From: Takashi Iwai <tiwai@xxxxxxx>
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@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
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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