linux-kernel - Re: [snd_hda_intel] snd_hda_intel causes high CPU lockup and system instability if mic disabled in BIOS on Lenovo P50

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Date:   Mon, 26 Nov 2018 09:24:46 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     "Alexander Kappner" <agk@...king.net>
Cc:     <Jim.Qu@....com>, <bhelgaas@...gle.com>,
        <guneshwor.o.singh@...el.com>, <perex@...ex.cz>,
        <hdegoede@...hat.com>, <lukas@...ner.de>,
        <alsa-devel@...a-project.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [snd_hda_intel] snd_hda_intel causes high CPU lockup and system instability if mic disabled in BIOS on Lenovo P50

On Mon, 26 Nov 2018 00:17:15 +0100,
Alexander Kappner wrote:
> 
> My Lenovo P50 laptop has a BIOS option to disable the microphone. When
> this option gets chosen, the snd_hda_intel driver causes high CPU load
> on a single kworker thread, spinning on "process_unsol_events", and
> system
> instability. This behavior occurs from the time that the snd_hda_intel
> module is loaded, irrespective of whether anything is attempting to access
> the mic. The sound output still works.
> 
> When in this state, the module cannot be removed cleanly; attempting to
> remove it (even without rmmod -f) triggers an oops.
> 
> I have attached two exemplary dmesg outputs. Strangely enough, the exact
> location of the oops varies, but further up the call chain, I always see
> process_unsol_events.
> 
> When the mic is not disabled in the BIOS, the module works stable,
> regardless whether or not the mic is muted in ALSA.
> 
> I wasn't able to pinpoint the root cause. Any pointers on where to
> start? Much appreciated.

Could you load snd-hda-intel driver with probe_only=1 option, and give
alsa-info.sh output (run it with --no-upload option)?  This should
leave only the codec probing without configuring, so we can see the
codec widget contents and check the emulator.


thanks,

Takashi