Revert "ALSA: usb-audio: Reduce latency at playback start"
authorLinus Torvalds <torvalds@linux-foundation.org>
Sat, 3 Jul 2021 05:05:52 +0000 (22:05 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Sat, 3 Jul 2021 05:05:52 +0000 (22:05 -0700)
commit4b820e167bf6f410ace479d8df5b15a574000e75
treee2bcfe89b46608d89972d539d27958705350085c
parentd6b63b5b7d7f363c6a54421533791e9849adf2e0
Revert "ALSA: usb-audio: Reduce latency at playback start"

This reverts commit 9ce650a75a3b262c90789b42aedee8fc2ee04d53.

This commit causes watchdog lockups on my machine, and while I have no
idea what the cause is, it bisected right to this commit, and reverting
the change promptly fixes it.

At least occasionally one of the watchdog call traces was

  Call Trace:
    _raw_spin_lock_irqsave+0x35/0x40
    snd_pcm_period_elapsed+0x1b/0xa0 [snd_pcm]
    snd_usb_endpoint_start+0x1a0/0x3c0 [snd_usb_audio]
    start_endpoints+0x23/0x90 [snd_usb_audio]
    snd_usb_substream_playback_trigger+0x7b/0x1a0 [snd_usb_audio]
    snd_pcm_common_ioctl+0x1c44/0x2360 [snd_pcm]
    snd_pcm_ioctl+0x2e/0x40 [snd_pcm]
    __se_sys_ioctl+0x72/0xc0
    do_syscall_64+0x4c/0xa0
    entry_SYSCALL_64_after_hwframe+0x44/0xae

so presumably it's a locking error on that substream spinlock that
snd_pcm_period_elapsed() takes.  But at this point I just want to have a
working system so that I can continue the merge window work tomorrow.

Cc: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
sound/usb/pcm.c