[Greg Ward]

...

What would be *really* spiffy is to provide a way for externally-triggered thread dumps. This is one of my top two Java features [1]. The way this works in Java is a bit awkward -- "kill -QUIT" the Java process and it writes a traceback for every running thread to stdout -- but it works. Something similar ought to be possible for Python, although optional (because Python apps can handle signals themselves, unlike Java apps).

It could be as simple as this: calling

sys.enablethreaddump(signal=signal.SIGQUIT)

from the program enables externally-triggered thread dumps via the specified signal.

See the link in my original post to Florent's Zope deadlock debugger. Things like the above are easy enough to create _given_ a bit of C code in the core to build on. [Phillip J. Eby]

Couldn't this just be done with traceback.print_stack(), given the _current_frames() facility?

Right.

About the only real problem with it is that the other threads can keep running while you're trying to print the stack dumps.

I don't know that it matters. If you're debugging a deadlocked thread, its stack isn't going to change. If you're trying to find out where unexpected time is getting swallowed, statements in the offending loop(s) are still going to show up in the stack trace.

I suppose you could set the check interval really high and then restore it afterwards as a sneaky way of creating a critical section. Unfortunately, there's no getcheckinterval().

sys.getcheckinterval() was added in Python 2.3.

Which reminds me, btw, it would be nice while we're adding more execution control functions to have a way to get the current trace hook and profiling hook, not to mention ways to set them on non-current threads. You can do these things from C of course; I mean accessible as part of the Python API.

Huh. It didn't remind me of those at all <wink>.

At 10:03 AM 3/8/05 +0000, Michael Hudson wrote:

"Phillip J. Eby" writes:

...

Which reminds me, btw, it would be nice while we're adding more execution control functions to have a way to get the current trace hook and profiling hook,

Well, there's the f_trace member of frame objects, but I honestly can't remember what it's for...

It sets the *local* trace function, which is only active if a *global* trace function is set for the thread. The global trace function is the thing you can't get at from Python.