[alsa-devel] [REGRESSION 5.3] WARNING: pulseaudio/1297 still has locks held!

[Russell King - ARM Linux admin]

When upgrading from 5.2 to 5.3, I now encounter this error after boot:

====================================
WARNING: pulseaudio/1297 still has locks held!
5.3.0+ #1826 Not tainted
------------------------------------
1 lock held by pulseaudio/1297:
 #0: ee815308 (&hcp->lock){....}, at: hdmi_codec_startup+0x20/0x130

stack backtrace:
CPU: 0 PID: 1297 Comm: pulseaudio Not tainted 5.3.0+ #1826
Hardware name: Marvell Dove (Cubox)
[<c0017b4c>] (unwind_backtrace) from [<c0014d10>] (show_stack+0x10/0x14)
[<c0014d10>] (show_stack) from [<c00a2d18>] (futex_wait_queue_me+0x13c/0x19c)
[<c00a2d18>] (futex_wait_queue_me) from [<c00a3630>] (futex_wait+0x184/0x24c)
[<c00a3630>] (futex_wait) from [<c00a5e1c>] (do_futex+0x334/0x598)
[<c00a5e1c>] (do_futex) from [<c00a62e8>] (sys_futex_time32+0x118/0x180)
[<c00a62e8>] (sys_futex_time32) from [<c0009000>] (ret_fast_syscall+0x0/0x54)
Exception stack(0xebd31fa8 to 0xebd31ff0)
1fa0:                   00000000 ffffffff 000c8748 00000189 00000001 00000000
1fc0: 00000000 ffffffff 00000000 000000f0 00000000 00000000 00000000 00056200
1fe0: 000000f0 beac03a8 b6d6c835 b6d6f456

This seems to be caused by:

  eb1ecadb7f67 ("ASoC: hdmi-codec: re-introduce mutex locking")

which holds a mutex and returns to userspace.  Meanwhile, userspace
issues a futex operation, which ends up in futex_wait_queue_me().

futex_wait_queue_me() can wait, and if the system will be hibernating,
is a potential hibernation point.  One of the requirements there is
that no locks shall be held, and the freezer code verifies that by
calling debug_check_no_locks_held().  With lockdep enabled, it reveals
that hdmi-codec is indeed holding a lock.

Reverting this commit solves the problem.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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