
from mosaic import *
OS2023(10)


slideshow('10.1')


demo('pc-sem', 'c/pc-sem.c', libs=['thread.h', 'thread-sync.h'])


model('m/pc-sem.py', check=True)

 1N, Tp, Tc = 2, 3, 3
 2
 3def Tproduce(nm):
 4  while not (heap.empty > 0):  # P(empty)
 5    sys_sched()
 6  heap.empty -= 1
 7  sys_sched()
 8
 9  sys_write('(')
10  sys_sched()
11
12  heap.fill += 1  # V(fill)
13
14def Tconsume(nm):
15  while not (heap.fill > 0):  # P(fill)
16    sys_sched()
17  heap.fill -= 1
18  sys_sched()
19
20  sys_write(')')
21  sys_sched()
22
23  heap.empty += 1  # V(empty)
24
25def main():
26  heap.fill = 0
27  heap.empty = N
28
29  for i in range(Tp):
30    sys_spawn(Tproduce, f'Tp{i+1}')
31  for i in range(Tc):
32    sys_spawn(Tconsume, f'Tc{i+1}')
33
34# Outputs:
35# (()())
36# (())()
37# ()(())
38# ()()()

10. 并发控制：同步 (2)¶