Reducing SIGINFO verbosity

From: Michael Gmelin <>
Date: Thu, 20 May 2021 16:01:55 UTC

I'm leaving this here, mostly so that others (or future me) can google
it up.

Traditionally, CTRL-t would give a one-line output + whatever the
process specific signal handler comes up with:

  # sleep 120 <--- hits CTRL-t
  load: 0.27  cmd: sleep 38162 [nanslp] 0.64r 0.00u 0.00s 0% 1780k
  sleep: about 119 second(s) left out of the original 120

  # cat <--- hits CTRL-t
  load: 0.02  cmd: cat 24379 [ttyin] 0.63r 0.00u 0.00s 0% 2308k

On 13 I get:

  # sleep 120 <--- hits CTRL-t
  load: 0.12  cmd: sleep 3241 [nanslp] 0.52r 0.00u 0.00s 0% 2172k
  mi_switch+0xc1 sleepq_catch_signals+0x2e6 sleepq_timedwait_sig+0x12
  _sleep+0x199 kern_clock_nanosleep+0x1e1 sys_nanosleep+0x3b
  amd64_syscall+0x10c fast_syscall_common+0xf8 sleep: about 119
  second(s) left out of the original 120

  # cat <--- hits CTRL-t
  load: 0.09  cmd: cat 3240 [ttyin] 0.23r 0.00u 0.00s 0% 2300k
  mi_switch+0xc1 sleepq_catch_signals+0x2e6 sleepq_wait_sig+0x9
  _cv_wait_sig+0xe4 tty_wait+0x1c ttydisc_read+0x2ac ttydev_read+0x56
  devfs_read_f+0xd5 dofileread+0x81 sys_read+0xbc amd64_syscall+0x10c

which is quite way too verbose when checking the progress of
long-running processes, like cp, dd, or poudriere. Especially as CTRL-t
is part of the user experience to me - I use it to interact with the
machine outside of debugging software issues.


  sysctl kern.tty_info_kstacks=0
  echo kern.tty_info_kstacks=0 >>/etc/sysctl.conf

fixes this permanently.

Apparently, this was enabled by default on purpose[0], so that people
find the feature (which certainly worked ^_^), but I think it would
been worth mentioning the sysctl somewhere in the release notes/errata,
so that people understand how to disable it again.



Michael Gmelin