Using /proc to get a process' current stack trace

by cirowrcon 10/15/2018, 12:45 PMwith 66 comments

by drewg123on 10/15/2018, 3:05 PM

FWIW, the equivalent in FreeBSD is 'procstat -kk $PID' Eg:

  % procstat -kk 5592

  PID    TID COMM                TDNAME              KSTACK                   
 5592 103222 less                -
mi_switch+0xe1 sleepq_catch_signals+0x405 sleepq_wait_sig+0xf _cv_wait_sig+0x154 tty_wait+0x1c ttydisc_read+0x1f2 ttydev_read+0x64 devfs_read_f+0xdc dofileread+0x95 sys_read+0xc3 amd64_syscall+0x369 fast_syscall_common+0x101

procstat can also do interesting things, like show current rusage state:

  % procstat -r 5592
  PID COMM             RESOURCE                          VALUE
 5592 less             user time                    00:00:00.010805
 5592 less             system time                  00:00:00.002444
 5592 less             maximum RSS                             3172 KB
 5592 less             integral shared memory                   192 KB
 5592 less             integral unshared data                    80 KB
 5592 less             integral unshared stack                  256 KB
 5592 less             page reclaims                            199
 5592 less             page faults                                0
 5592 less             swaps                                      0
 5592 less             block reads                                4
 5592 less             block writes                               0
 5592 less             messages sent                              0
 5592 less             messages received                          0
 5592 less             signals received                           0
 5592 less             voluntary context switches                59
 5592 less             involuntary context switches               0

by lixtraon 10/15/2018, 3:01 PM

If you are running java instead of a c program the proc stacktrace shows you just the virtual machine state. You can still get a stacktrace of your java threads[1].

How about other languages? Python, ruby?

[1] https://stackoverflow.com/questions/4876274/kill-3-to-get-ja...

by indigodaddyon 10/15/2018, 6:07 PM

Nicely formatted site. Anyone know if/what static site generator/theme is being used? Couldn't find anything on the footer, site tags, or his GitHub that would reveal that...

by ktpsnson 10/15/2018, 8:52 PM

Note, the GNU debugger (gdb) can attach to running processes. This should give you a stack trace with readable addresses, cf. https://stackoverflow.com/questions/2308653/can-i-use-gdb-to...

by _pmf_on 10/15/2018, 3:12 PM

My favorite proc hack: https://news.ycombinator.com/item?id=17061499

by jhallenworldon 10/15/2018, 3:10 PM

I want this capability for embedded ARM systems. I should be able to call a function to have the current stack trace printed:

https://communities.mentor.com/thread/16468

by AlphaWeaveron 10/15/2018, 4:16 PM

This is a very well written and formatted article... I found it easy to read!

by Annataron 10/15/2018, 12:54 PM

Instead of teaching people how to do this portably across all UNIX-like systems, by sending SIGABRT to the process, the article is steeping them in GNU/Linux only way of doing things. This feels exactly like the '90's of the past century, where a lot of people with computer-related careers had no idea that there were other operating systems and other ways of doing things (better): an intel-based PC tin bucket with Windows was the one and only truth for them. Now it's exactly the same except Windows has been replaced with GNU/Linux. 28 years later and the only advancement some people have made is running the proverbial sed 's/Windows/Linux/g'.