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Date:   Sat, 29 Jan 2022 17:47:04 +0300
From:   Alexander Sergeyev <sergeev917@gmail.com>
To:     Takashi Iwai <tiwai@suse.de>
Cc:     Jeremy Szu <jeremy.szu@canonical.com>, tiwai@suse.com,
        "moderated list:SOUND" <alsa-devel@alsa-project.org>,
        Kailang Yang <kailang@realtek.com>,
        open list <linux-kernel@vger.kernel.org>,
        Huacai Chen <chenhuacai@kernel.org>,
        Jian-Hong Pan <jhp@endlessos.org>,
        Hui Wang <hui.wang@canonical.com>,
        PeiSen Hou <pshou@realtek.com>
Subject: Re: [PATCH 1/4] ALSA: hda/realtek: fix mute/micmute LEDs for HP 855
 G8
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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?