I have timidity installed, but I really do not use it for anything I
think. Maybe a webbrowser is using for something, but midi use on
webpages is rare AFAIK.

Maybe it is somehow to some timidity upgrade, but I do not see anything
in /var/log/apt/history.log about timidity for last 3-4 weeks, and the
100% CPU usage thing started just few hours ago out of the blue.

strace -tt -f -p `pidof timidity` shows constant flow of:

20:30:50.347225 ioctl(6, SNDRV_SEQ_IOCTL_GET_QUEUE_STATUS, 0x2760380) = 0
20:30:50.347256 poll([{fd=6, events=POLLIN}], 1, 0) = 0 (Timeout)
20:30:50.347290 ioctl(6, SNDRV_SEQ_IOCTL_GET_QUEUE_STATUS, 0x2760380) = 0
20:30:50.347321 poll([{fd=6, events=POLLIN}], 1, 0) = 0 (Timeout)
20:30:50.347353 ioctl(6, SNDRV_SEQ_IOCTL_GET_QUEUE_STATUS, 0x2760380) = 0
20:30:50.347384 poll([{fd=6, events=POLLIN}], 1, 0) = 0 (Timeout)
20:30:50.347416 ioctl(6, SNDRV_SEQ_IOCTL_GET_QUEUE_STATUS, 0x2760380) = 0
20:30:50.347447 poll([{fd=6, events=POLLIN}], 1, 0) = 0 (Timeout)
20:30:50.347480 ioctl(6, SNDRV_SEQ_IOCTL_GET_QUEUE_STATUS, 0x2760380) = 0
20:30:50.347510 poll([{fd=6, events=POLLIN}], 1, 0) = 0 (Timeout)
20:30:50.347545 ioctl(6, SNDRV_SEQ_IOCTL_GET_QUEUE_STATUS, 0x2760380) = 0
20:30:50.347573 poll([{fd=6, events=POLLIN}], 1, 0) = 0 (Timeout)


It is started by the standard init script.

timidity  2093  4.9  0.0 138548  8080 ?        RL   sty25 366:34 /usr/bin/timidity -Os -iAD

Doing /etc/init.d/timidity stop; /etc/init.d/timidity start; resolved the problem,
but it shouldn't happen anyway in the first place.

Dear Debian maintainers, I can confirm that this bug is present in
up-to-date Stretch and was present in Jessie as well. I didn't find any
way to reproduce it, just get it launched and wait for a few hours.

If you could please fix it, it would be really much appreciated.

Thanks,
Olivier