Re: Dumping the state of a deadlocked process

Dennis Lee Bieber wrote:
On 6 Oct 2006 12:59:31 -0700, andre.naess@xxxxxxxxx declaimed the
following in comp.lang.python:

I'm currently having some issues with a process getting deadlocked. The
problem is that the only way I can seem to find information about where
it deadlocks is by making a wild guess, insert a pdb.set_trace() before
this point, and then step until it locks up, hoping that I've guessed
right.

I presume the process is using threads? If it is truly deadlocked,
then you must have some mutual calls to lock objects somewhere... It
would seem that rather than just randomly inserting debug statements you
should surround each call to a lock with statements.

print "Locking xyz"
xyz.acquire() #or whatever the syntax is
print "Locked xyz"



print "Releasing xyz"
xyz.release()
print "Released xyz"


You'd need something like that around any potentially blocking
operation -- queue operations, subprocess operations, socket
operations... Rather than print statements you may wish to implement it
via the logging module.

If you don't mind a potentially large log file, use the pyconquer
module I maintain here: http://projects.amor.org/misc/wiki/PyConquer
which uses settrace to do the logging in a much more readable and
manageable way than printlining. Try an initial run using the default
settings to narrow down the culprit, and then a run with C events
turned on if the first run wasn't enough. It should help out even if
your program is not multi-threaded, but it realy shines with threads.
:)


Robert Brewer
System Architect
Amor Ministries
fumanchu@xxxxxxxx

P.S. Oh, and ignore the times in the output for now; that's still work
in progress.

.