[10.4] thread synchronization --Lock, RLock

 1 #!/user/bin/env python
 2 # -*- coding:utf-8 -*-
 3 
 4 import dis
 5 import threading
 6 from threading import Lock
 7 total = 0
 8 lock = Lock()
 9 
10 
11 def add():
12     global total
13     global lock
14     for i in range(1000000):
15         # 获取锁
16         lock.acquire()
17         total += 1
18         # 释放锁
19         lock.release()
20 
21 
22 def desc():
23     global total
24     global lock
25     for i in range(1000000):
26         # 获取锁
27         lock.acquire()
28         total -= 1
29         # 释放锁
30         lock.release()
31 
32 
33 thread1 = threading.Thread(target=add)
34 thread2 = threading.Thread(target=desc)
35 
36 thread1.start()
37 thread2.start()
38 
39 
40 def add1(a):
41     a += 1
42 
43 
44 def desc1(a):
45     a -= 1
46 
47 
48 """
49 1.load a
50 2.load 1
51 3.+(-)
52 4.赋值给a
53 """
54 print(dis.dis(add1))
55 print(dis.dis(desc1))
56 
57 thread1.join()
58 thread2.join()
59 
60 print(total)

 41           0 LOAD_FAST                0 (a)
              2 LOAD_CONST               1 (1)
              4 INPLACE_ADD
              6 STORE_FAST               0 (a)
              8 LOAD_CONST               0 (None)
             10 RETURN_VALUE
None
 45           0 LOAD_FAST                0 (a)
              2 LOAD_CONST               1 (1)
              4 INPLACE_SUBTRACT
              6 STORE_FAST               0 (a)
              8 LOAD_CONST               0 (None)
             10 RETURN_VALUE
None

C:\Users\Administrator\Python\imooc>python demo.py
 41           0 LOAD_FAST                0 (a)
              2 LOAD_CONST               1 (1)
              4 INPLACE_ADD
              6 STORE_FAST               0 (a)
              8 LOAD_CONST               0 (None)
             10 RETURN_VALUE
None
 45           0 LOAD_FAST                0 (a)
              2 LOAD_CONST               1 (1)
              4 INPLACE_SUBTRACT
              6 STORE_FAST               0 (a)
              8 LOAD_CONST               0 (None)
             10 RETURN_VALUE
None
0

C:\Users\Administrator\Python\imooc>python demo.py
 41           0 LOAD_FAST                0 (a)
              2 LOAD_CONST               1 (1)
              4 INPLACE_ADD
              6 STORE_FAST               0 (a)
              8 LOAD_CONST               0 (None)
             10 RETURN_VALUE
None
 45           0 LOAD_FAST                0 (a)
              2 LOAD_CONST               1 (1)
              4 INPLACE_SUBTRACT
              6 STORE_FAST               0 (a)
              8 LOAD_CONST               0 (None)
             10 RETURN_VALUE
None
0

 

1. Lock affect performance

2. The lock will lead to deadlock

 

RLock

1  # ! / The User / bin / env Python 
2  # - * - Coding: UTF-8 - * - 
3  
4  Import Threading
 5  # RLOCK, in the same thread which can be called many times in a row acquire, acquire must pay attention to the number of to and the number of release equal 
6  # between threads or related competing 
. 7  from Threading Import RLOCK
 . 8 Total = 0
 . 9 Lock = RLOCK ()
 10  
. 11  
12 is  DEF the Add ():
 13 is      Global Total
 14      Global Lock
 15      for I in Range (1000000 ):
16          # acquire the lock 
. 17          lock.acquire ()
 18 is          lock.acquire ()
 . 19          Total +. 1 =
 20 is          # releases the lock 
21 is          lock.release ()
 22 is          lock.release ()
 23 is  
24  
25  DEF desc ():
 26 is      Global Total
 27      Global lock
 28      for I in Range (1000000 ):
 29          # acquire the lock 
30          lock.acquire ()
 31 is          Total -. 1 =
 32          # release lock 
33         lock.release()
34 
35 
36 thread1 = threading.Thread(target=add)
37 thread2 = threading.Thread(target=desc)
38 
39 thread1.start()
40 thread2.start()
41 
42 thread1.join()
43 thread2.join()
44 
45 print(total)

0