Re: kern/56059: speaker(4): system hangs if tone < 100 Hz (_SC_CLK_TCK) is played

[RVP <rvp%SDF.ORG@localhost>]

What I forgot to mention in the bug report was that this speaker
is a synthesized device--ie. this is not an old-fashioned PPI PC
speaker. (As far as I can figure it out, my system--an Asus X202E
laptop--doesn't have a physical PC speaker at all):

$ fgrep audio /var/run/dmesg.boot 
hdaudio0 at pci0 dev 27 function 0: HD Audio Controller
hdaudio0: interrupting at msi1 vec 0
hdafg0 at hdaudio0: vendor 1106 product 8446
audio0 at hdafg0: playback, capture, full duplex, independent
audio0: slinear_le:16 2ch 48000Hz, blk 1920 bytes (10ms) for playback
audio0: slinear_le:16 2ch 48000Hz, blk 1920 bytes (10ms) for recording
spkr0 at audio0: PC Speaker (synthesized)
hdafg1 at hdaudio0: vendor 8086 product 2806
$

So, the sound is being synthesized in sys/dev/audio/audiobell.c
and this is really an audio(4) bug.

Poking around in the sources a bit led me to wonder if generating
(small) samples for tones < 100Hz was leading to a buffer underrun
somewhere. And, it seems this is so: raising the hw.audio0.blk_ms
value "fixes" the kernel hang for me. A value of 15 ms suffices,
but, then the generated tones seemed "off tune", so I've raised it to
the max. it will go to on my HW (8KB -- ~42 secs):

# sudo sysctl -w hw.audio0.blk_ms=50

Maybe this will help narrow down what needs to be fixed in the
code.

-RVP