view contrib/showstack.py @ 40036:acf5dbe39478

showstack: also handle SIGALRM

This is looking *very* handy when debugging mysterious hangs in a
test: you can wrap a hanging invocation in

  `perl -e 'alarm shift @ARGV; exec @ARGV' 1`

for example, a hanging `hg pull` becomes

  `perl -e 'alarm shift @ARGV; exec @ARGV' 1 hg pull`

where the `1` is the timeout in seconds before the process will be hit
with SIGALRM. After making that edit to the test file, you can then
use --extra-config-opt on run-tests.py to globaly enable showstack
during the test run, so you'll get full stack traces as you force your
hg to exit.

I wonder (but only a little, not enough to take action just yet) if we
should wire up some scaffolding in run-tests itself to automatically
wrap all commands in alarm(3) somehow to avoid hangs in the future?

Differential Revision: https://phab.mercurial-scm.org/D4870

# showstack.py - extension to dump a Python stack trace on signal
#
# binds to both SIGQUIT (Ctrl-\) and SIGINFO (Ctrl-T on BSDs)
"""dump stack trace when receiving SIGQUIT (Ctrl-\) and SIGINFO (Ctrl-T on BSDs)
"""

from __future__ import absolute_import, print_function
import signal
import sys
import traceback

def sigshow(*args):
    sys.stderr.write("\n")
    traceback.print_stack(args[1], limit=10, file=sys.stderr)
    sys.stderr.write("----\n")

def sigexit(*args):
    sigshow(*args)
    print('alarm!')
    sys.exit(1)

def extsetup(ui):
    signal.signal(signal.SIGQUIT, sigshow)
    signal.signal(signal.SIGALRM, sigexit)
    try:
        signal.signal(signal.SIGINFO, sigshow)
    except AttributeError:
        pass