[PATCH 1/4] ALSA: hda/realtek: fix mute/micmute LEDs for HP 855 G8

[Alexander Sergeyev]

On Wed, Jan 26, 2022 at 04:24:36PM +0100, Takashi Iwai wrote:
> > Given that the CPU number is the same in alc_update_coefex_idx(), it seems 
> > these calls execution is interrupted and interleaved on the same core.
> > And, actually, there are two LEDs to set (mute and micmute). Am I onto 
> > something here?
> That's an interesting finding, and yes, such a race is quite
> possible. Below is a quick fix as an attempt to cover it.
> Could you give it a try?

Well, results are somewhat mixed.

With the supplied patch (with a mutex), the original fixup 91502a9a0b0d ("ALSA: 
hda/realtek: fix speakers and micmute on HP 855 G8") is no longer needed for 
speakers to work. So, the original timing issue is identified now.

But unbind-bind problems with IO_PAGE_FAULT and "out of range cmd" are not 
eliminated. IO_PAGE_FAULT are often logged without accompanying "out of range 
cmd". And after adding debugging printk() I haven't managed to trigger "out of 
range cmd" yet. But IO_PAGE_FAULT are more easily triggered.

Are there ways to trace origins of IO_PAGE_FAULT itself?