The formation of the Python deadlock

How does a Python deadlock form?

Deadlock refers to two or more processes in the process of execution, because of the competition for resources caused by a mutual waiting phenomenon, if there is no external force, they will not go forward. At this point the system is in a deadlock state or the system generates a deadlock, and these processes, which are always waiting on each other, are called deadlock processes. Because the resource consumption is mutually exclusive, when a process requests resources, so that the process without external assistance, never allocated the necessary resources and can not continue to run, which creates a special phenomenon of deadlock.

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Created on 2012-9-8

@author: walfred

@module: Thread. TreadTest5

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Import threading

Countera = 0

Counterb = 0

Mutexa = Threading. Lock ()

MUTEXB = Threading. Lock ()

Class MyThread (threading. Thread):

def __init__ (self):

Threading. Thread.__init__ (self)

def run (self):

SELF.FUN1 ()

Self.fun2 ()

def fun1 (self):

Global Mutexa, Mutexb

If Mutexa.acquire ():

Print "I am%s, get res:%s"% (Self.name, "ResA")

If Mutexb.acquire ():

Print "I am%s, get res:%s"% (Self.name, "Resb")

Mutexb.release ()

Mutexa.release ()

def fun2 (self):

Global Mutexa, Mutexb

If Mutexb.acquire ():

Print "I am%s, get res:%s"% (Self.name, "Resb")

If Mutexa.acquire ():

Print "I am%s, get res:%s"% (Self.name, "ResA")

Mutexa.release ()

Mutexb.release ()

if __name__ = = "__main__":

For I in range (0, 100):

My_thread = MyThread ()

My_thread.start ()

The code shows the two functional functions of a thread that acquire another competing resource after acquiring a competing resource, and we look at the result of the operation:

I am Thread-1, get Res:resa

I am Thread-1, get res:resb

I am Thread-2, get Res:resai am Thread-1, get res:resb

The program has been suspended there, and this phenomenon we call "deadlock."

Some of the code originates from Codego.net and is truncated.

The formation of the Python deadlock