[Python-bugs-list] [Bug #125673] PyThreadState_Delete: invalid tstate (Unix only?)

[noreply@sourceforge.net]

Bug #125673, was updated on 2000-Dec-13 08:25
Here is a current snapshot of the bug.

Project: Python
Category: Threads
Status: Open
Resolution: None
Bug Group: Platform-specific
Priority: 5
Submitted by: gvanrossum
Assigned to : gvanrossum
Summary: PyThreadState_Delete: invalid tstate (Unix only?)

Details: I am working on a simple couroutine/generator package using
threads,
to prototype the API.  It seems to be working fine, except it is
exposing a hard-to-find bug in the threadstate code.  The following
script[*] contains the API implementation and a simple example based on
Tim's "fringe()" code.  When I run the example, I *sometimes* get:

    Segmentation fault

but *sometimes* I get:

    Fatal Python error: PyThreadState_Delete: invalid tstate
    Aborted

and *sometimes* it succeeds.  If I uncomment the raw_input("Exit?")
line at the end I never get an error.  The error behavior seems very
fickle: making almost arbitrary changes to the code can trigger it or
make it go away.  When I run it under gdb, I cannot reproduce the
problen, ever.  (Haven't I heard this before?)

The only clue is the fatal error message: it seems to be a race
condition at thread termination.  But how to debug this?

_____
[*] I'm not including the script here.
I can mail it to interested parties though.  For my own reference:
Subject: [Pycabal] Mysterious thread bug
To: <cabal>
Date: Thu, 16 Nov 2000 16:21:12 -0500


Follow-Ups:

Date: 2001-Jan-20 23:20
By: tim_one

Comment:
Guido, since we just fixed *a* thread termination problem (premature
clearing of "initialized" in pythonrun.c), and I've never seen this fail on
Windows, reassigning to you to see whether-- however unlikely it may seem
--this problem has gone away by magic now.

-------------------------------------------------------

Date: 2000-Dec-13 08:51
By: tim_one

Comment:
I was never able to provoke a problem on Windows using Guido's script, so
changed Group to Platform-specific and added "(Linux only?)" to Summary. 
Here's the script; assigned to Greg under the hope he can provoke a
problem:

import thread

class EarlyExit(Exception):
    pass

class main_coroutine:

    def __init__(self):
        self.id = 0
        self.caller = None
        self.value = None
        self.lock = thread.allocate_lock()
        self.lock.acquire()
        self.done = 0

    def __call__(self, value=None):
        cur = current()
        assert cur is not self
        self.caller = cur
        self.value = value
        self.lock.release()
        cur.lock.acquire()
        if self.done:
            raise EarlyExit
        return cur.value

all_coroutines = {thread.get_ident(): main_coroutine()}

def current():
    return all_coroutines[thread.get_ident()]

def suspend(value=None):
    cur = current()
    caller = cur.caller
    assert caller and caller is not cur
    caller.value = value
    caller.lock.release()
    cur.lock.acquire()
    return cur.value

nextid = 1

class coroutine(main_coroutine):

    def __init__(self, func, *args):
        global nextid
        self.id = nextid
        nextid = nextid + 1
        self.caller = current()
        boot = thread.allocate_lock()
        boot.acquire()
        thread.start_new_thread(self.run, (boot, func, args))
        boot.acquire()

    def run(self, boot, func, args):
        me = thread.get_ident()
        all_coroutines[me] = self
        self.lock = thread.allocate_lock()
        self.lock.acquire()
        self.done = 0
        boot.release()
        self.lock.acquire()
        if self.value:
            print "Warning: initial value %s ignored" % `value`
        try:
            apply(func, args)
        finally:
            del all_coroutines[me]
            self.done = 1
            self.caller.lock.release()

def fringe(list):
    tl = type(list)
    for item in list:
        if type(item) is tl:
            fringe(item)
        else:
            suspend(item)

def printinorder(list):
    c = coroutine(fringe, list)
    try:
        while 1:
            print c(),
    except EarlyExit:
        pass
    print

if __name__ == '__main__':
    printinorder([1,2,3])
    l = [1,2,[3,4,[5],6]]
    printinorder(l)
    #raw_input("Exit?")

-------------------------------------------------------

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http://sourceforge.net/bugs/?func=detailbug&bug_id=125673&group_id=5470