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

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# showstack.py - extension to dump a Python stack trace on signal

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#

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# binds to both SIGQUIT (Ctrl-\) and SIGINFO (Ctrl-T on BSDs)

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"""dump stack trace when receiving SIGQUIT (Ctrl-\) and SIGINFO (Ctrl-T on BSDs)

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"""

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from __future__ import absolute_import, print_function

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import signal

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import sys

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import traceback

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def sigshow(*args):

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    sys.stderr.write("\n")

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    traceback.print_stack(args[1], limit=10, file=sys.stderr)

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    sys.stderr.write("----\n")

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def sigexit(*args):

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    sigshow(*args)

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    print('alarm!')

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    sys.exit(1)

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def extsetup(ui):

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    signal.signal(signal.SIGQUIT, sigshow)

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    signal.signal(signal.SIGALRM, sigexit)

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    try:

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        signal.signal(signal.SIGINFO, sigshow)

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    except AttributeError:

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        pass