Hi Oleg

sqlobject-discuss-bounces@lists.sourceforge.net schrieb am 05.07.2007 11:31:56:

> On Thu, Jul 05, 2007 at 11:22:36AM +0200, bernhard.maeder@zkb.ch wrote:
> > The accesses are made in different threads, to objects of the same class
> > (MyClass in my example). One locks while resolving a ForeignKey in
> > _SO_foreignKey(), one locks in _SO_finishCreate() and the third one in the
> > selectresult's __iter__().
>
>    Can you do an experiment - create objects of OtherClass outside of
> _create() and assign them to foreign keys after the object has been fully
> created?
>


I've tried to produce an isolated example of my problem. I'm not yet sure if everything's needed in here, I'm still trying to buil it further down.

Things I noticed so far:

 - The _create seems not to have anything to do with it, as it locks even without one.
 - A higher number of threads increase the possibility for deadlocks.
 - I need to have two classes, MyClass1 and MyClass2, in order for the deadlock to occur.

To the code:
 - On my machine, the code deadlocks after some 10s of objects created.
 - The threadframe module may be downloaded here: http://www.majid.info/mylos/stories/2004/06/10/threadframe.html. Maybe you have some clever debugger that can do that for you... :-)

Thanks!
Bernhard

#****************************************************

import sqlobject
import threading
import time

sqlobject.sqlhub.processConnection = sqlobject.connectionForURI('mysql://XXX')


class Attribute(sqlobject.SQLObject):
    """
    Attribute class
    """    
    attributeSet = sqlobject.ForeignKey('AttributeSet')
   
    name = sqlobject.StringCol(default = '')
    value = sqlobject.StringCol(default = '')
   
class AttributeSet(sqlobject.SQLObject):
    """
    Attribute set class, contains attributes
    """
    attributes  = sqlobject.SQLMultipleJoin('Attribute')
   
    def _set_attributes(self, attrs):        
        # First clear...        
        for attr in self.attributes: attr.destroySelf()
       
        # ... then set.
        for k, v in attrs.items():
            Attribute(attributeSet = self, name = k, value = v)
       
    def _get_attributes(self):
        attrs = {}
        for attribute in list(self._SO_get_attributes()):
            attrs[attribute.name] = attribute.value
        return attrs
           

class MyClass1(sqlobject.SQLObject):
    """
    First class that uses an attribute set.
    """
    attrSet = sqlobject.ForeignKey('AttributeSet', default = None)    
   
    # I would want to create the attribute set here, but for
    # Oleg's suggestion, I'm doing it from the calling class.
   
    #def _create(self, *args, **kw):
        #super(MyClass1, self)._create(*args, **kw)        
       
        #self.attrSet = AttributeSet()
        #self.attrSet.attributes = dict(foo = 1, bar = 2)
       
       
class MyClass2(sqlobject.SQLObject):
    """
    Second class that uses an attribute set.
    """
    attrSet = sqlobject.ForeignKey('AttributeSet', default = None)
   
    #def _create(self, *args, **kw):
        #super(MyClass2, self)._create(*args, **kw)
       
        #self.attrSet = AttributeSet()        
        #self.attrSet.attributes = dict(foo = 1, bar = 2)        
       
# Create tables.
Attribute.createTable(ifNotExists = True)
AttributeSet.createTable(ifNotExists = True)
MyClass1.createTable(ifNotExists = True)
MyClass2.createTable(ifNotExists = True)


class MyThread(threading.Thread):      
    """
    A thread that produces instances of MyClass1 or Myclass2.
    """    
    def __init__(self, Klass):
        super(MyThread, self).__init__()
        self._Klass = Klass
   
    def run(self):
        print '%02d %02d %20s : Started' % (time.localtime().tm_min, time.localtime().tm_sec, threading.currentThread().getName())
        for i in range(100):
            mc = self._Klass()
            mc.attrSet = AttributeSet()        
            mc.attrSet.attributes = dict(foo = 1, bar = 2)    
               
            # Accessing these will result in a deadlock
            for key, value in mc.attrSet.attributes.items():
                pass
           
            if i % 10 == 0:
                print '%02d %02d %20s : %s' % (time.localtime().tm_min, time.localtime().tm_sec, threading.currentThread().getName(), i)


# Create some threads
threads = [MyThread(MyClass1) for i in range(10)] + [MyThread(MyClass2) for i in range(10)]

print 'Starting threads'

for t in threads: t.start()

time.sleep(10)
import threadframe, traceback, sys
frames = threadframe.threadframe()

print '-' * 72

for frame in frames:
    print '-' * 72
    print 'frame ref count = %d' % sys.getrefcount(frame)
    traceback.print_stack(frame, file=sys.stdout)

for t in threads: t.join()
   
print 'Done'
   
#****************************************************
   

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