【10.4】线程同步--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.用锁会影响性能

2.锁会引起死锁

RLock

 1 #!/user/bin/env python
 2 # -*- coding:utf-8 -*-
 3 
 4 import threading
 5 # RLock，在同一个线程里面，可以连续调用多次acquire，一定要注意acquire的次数要和release的次数相等
 6 # 线程间还是有相互竞争的关系
 7 from threading import RLock
 8 total = 0
 9 lock = RLock()
10 
11 
12 def add():
13     global total
14     global lock
15     for i in range(1000000):
16         # 获取锁
17         lock.acquire()
18         lock.acquire()
19         total += 1
20         # 释放锁
21         lock.release()
22         lock.release()
23 
24 
25 def desc():
26     global total
27     global lock
28     for i in range(1000000):
29         # 获取锁
30         lock.acquire()
31         total -= 1
32         # 释放锁
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