Andrew Cooke | Contents | Latest | RSS | Twitter | Previous | Next

C[omp]ute

Welcome to my blog, which was once a mailing list of the same name and is still generated by mail. Please reply via the "comment" links.

Always interested in offers/projects/new ideas. Eclectic experience in fields like: numerical computing; Python web; Java enterprise; functional languages; GPGPU; SQL databases; etc. Based in Santiago, Chile; telecommute worldwide. CV; email.

Personal Projects

Lepl parser for Python.

Colorless Green.

Photography around Santiago.

SVG experiment.

Professional Portfolio

Calibration of seismometers.

Data access via web services.

Cache rewrite.

Extending OpenSSH.

C-ORM: docs, API.

Last 100 entries

[Link, Politics] Why identity politics benefits the right more than the left; SSH Forwarding; Low Cost Payroll Service for Cat Soft LLC; A Specification For Repeating Events; A Fight for the Soul of Science; [Science, Book, Link] Lost In Math; OpenSuse Leap 15 Network Fixes; Update; [Book] Galileo's Middle Finger; [Bike] Chinese Carbon Rims; [Bike] Servicing Shimano XT Front Hub HB-M8010; [Bike] Aliexpress Cycling Tops; [Computing] Change to ssh handling of multiple identities?; [Bike] Endura Hummvee Lite II; [Computing] Marble Based Logic; [Link, Politics] Sanity Check For Nuclear Launch; [Link, Science] Entropy and Life; [Link, Bike] Cheap Cycling Jerseys; [Link, Music] Music To Steal 2017; [Link, Future] Simulated Brain Drives Robot; [Link, Computing] Learned Index Structures; Solo Air Equalization; Update: Higher Pressures; Psychology; [Bike] Exercise And Fuel; Continental Race King 2.2; Removing Lowers; Mnesiacs; [Maths, Link] Dividing By Zero; [Book, Review] Ray Monk - Ludwig Wittgenstein: The Duty Of Genius; [Link, Bike, Computing] Evolving Lacing Patterns; [Jam] Strawberry and Orange Jam; [Chile, Privacy] Biometric Check During Mail Delivery; [Link, Chile, Spanish] Article on the Chilean Drought; [Bike] Extended Gear Ratios, Shimano XT M8000 (24/36 Chainring); [Link, Politics, USA] The Future Of American Democracy; Mass Hysteria; [Review, Books, Links] Kazuo Ishiguro - Never Let Me Go; [Link, Books] David Mitchell's Favourite Japanese Fiction; [Link, Bike] Rear Suspension Geometry; [Link, Cycling, Art] Strava Artwork; [Link, Computing] Useful gcc flags; [Link] Voynich Manuscript Decoded; [Bike] Notes on Servicing Suspension Forks; [Links, Computing] Snap, Flatpack, Appimage; [Link, Computing] Oracle is leaving Java (to die); [Link, Politics] Cubans + Ultrasonics; [Book, Link] Laurent Binet; VirtualBox; [Book, Link] No One's Ways; [Link] The Biggest Problem For Cyclists Is Bad Driving; [Computing] Doxygen, Sphinx, Breathe; [Admin] Brokw Recent Permalinks; [Bike, Chile] Buying Bearings in Santiago; [Computing, Opensuse] Upgrading to 42.3; [Link, Physics] First Support for a Physics Theory of Life; [Link, Bike] Peruvian Frame Maker; [Link] Awesome Game Theory Tit-For-Tat Thing; [Food, Review] La Fabbrica - Good Italian Food In Santiago; [Link, Programming] MySQL UTF8 Broken; [Link, Books] Latin American Authors; [Link, Computing] Optimizatin Puzzle; [Link, Books, Politics] Orwell Prize; [Link] What the Hell Is Happening With Qatar?; [Link] Deep Learning + Virtual Tensor Machines; [Link] Scaled Composites: Largest Wingspan Ever; [Link] SCP Foundation; [Bike] Lessons From 2 Leading 2 Trailing; [Link] Veg Restaurants in Santiago; [Link] List of Contemporary Latin American Authors; [Bike] FTHR; [Link] Whoa - NSA Reduces Collection (of US Residents); [Link] Red Bull's Breitbart; [Link] Linux Threads; [Link] Punycode; [Link] Bull / Girl Statues on Wall Street; [Link] Beautiful Chair Video; Update: Lower Pressures; [Link] Neat Python Exceptions; [Link] Fix for Windows 10 to Avoid Ads; [Link] Attacks on ZRTP; [Link] UK Jazz Invasion; [Review] Cuba; [Link] Aricle on Gender Reversal of US Presidential Debate; {OpenSuse] Fix for Network Offline in Updater Applet; [Link] Parkinson's Related to Gut Flora; Farellones Bike Park; [Meta] Tags; Update: Second Ride; Schwalbe Thunder Burt 2.1 v Continental X-King 2.4; Mountain Biking in Santiago; Books on Ethics; Security Fail from Command Driven Interface; Everything Old is New Again; Interesting Take on Trump's Lies; Chutney v6; References on Entropy; Amusing "Alexa.." broadcast; The Shame of Chile's Education System; Playing mp4 gifs in Firefox on Opensuses Leap 42.2; Concurrency at Microsoft

© 2006-2017 Andrew Cooke (site) / post authors (content).

Debugging A Hung (Spinning) Python Process

From: andrew cooke <andrew@...>

Date: Mon, 31 May 2010 09:46:01 -0400

I left a Python script running at the client's, overnight, expecting
everything to be ready in the morning.  But when I checked next day the CPU
was pegged at 100% and the log indicated no progress since 1am.  Clearly the
Python code had a bug and was "spinning" in a tight loop.

The problem, then, was to find out what code was being executed.  Luckily
there's a very neat solution, that I've used before, that does exactly this.
It's described in an answer by "spiv" at
http://stackoverflow.com/questions/132058/getting-stack-trace-from-a-running-python-application

That describes how to connect gdb to the process ("gdb -p PID") and dump a
Python stack trace ("pystack").  All that you need to do is create a .gdbinit
file with the contents given here -
http://svn.python.org/projects/python/trunk/Misc/gdbinit

With a stack trace it was easy to see the error in my code - and it was a
tight loop, and it depended explicitly on the time of day, which is why I had
not seen it before. :o)

Andrew

Update

From: andrew cooke <andrew@...>

Date: Thu, 31 May 2018 21:16:09 -0400

This is now simpler.

You need to follow the instructions at
https://devguide.python.org/gdb/ - basically put

  add-auto-load-safe-path /path/to/checkout

in ~/.gdbinit

Then connect with gdb -p PID and use the commands described in the
link.

There is one extra step for VMs.  You need to link the python-dgb.py
in the checkout directory to the bin directory for the virtualenv, and
the name MUST MATCH the python in use (so python-3.5, if used, not
simply python)

For example, ths worked for me:

  ln -s /home/andrew/pkg/Python-3.5.1/python-gdb.py env/bin/python3.5-gdb.py

Andrew

Comment on this post