Python多进程,同步互斥,信号量,锁补充上一篇文章

进程补充

进程间的信号

信号是唯一的异步通信方法

一个进程向另一个进程发送一个信号来传递某种信息，接受者根据传递的信息来做相应的事

$ kill -l查看系统信号说明

$ kill -9 pid号对进程发送信号

信号名称	说明
1) SIGHUP	连接断开
2) SIGINT	ctrl+c
3) SIGQUIT	ctrl+\
20) SIGTSTP	ctrl+z
9) SIGKILL	终止进程
19) SIGSTOP	暂停进程
26) SIGVTALRM	时钟信号
17) SIGCHLD	子进程退出时给父进程发的信号

在Python中import signal可以获取信号

os.kill(pid, sig)
- 功能：发送信号
- 参数
  - pid：要发送信号的PID号
  - sig ：信号名称

 
  
import os
import signal
os.kill(12345,signal.SIGKILL) #杀死进程

View Code

signal.alarm(time)

个人理解：把发送信号的信息告知系统内核，应用层程序继续运行，时间到之后利用内核告知应用层程序进行处理

功能：非阻塞函数，向自身进程发送一个时钟信号
参数：time->整型时间秒

 
  
  import signal
  import time
  signal.alarm(3)#3秒后向自身发送一个时钟信号
  while True:
      time.sleep(1)
      print("等待时钟信号")
      
  '''打印结果
  等待时钟信号
  等待时钟信号
  闹钟
  '''

View Code

 
  
  signal.alarm(3)#3秒后向自身发送一个时钟信号
  time.sleep(2)
  signal.alarm(5)#进程只有一个时钟信号，第二个会覆盖上面的时钟信号
  while True:
      time.sleep(1)
      print("等待时钟信号")
      
  '''打印结果
  等待时钟信号
  等待时钟信号
  等待时钟信号
  等待时钟信号
  闹钟
  '''

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signal.pause()

功能：阻塞进程，然后等待信号
signal.signal(signum, handler)

功能：处理信号
参数

signum：要处理的信号
- handler：信号的处理方法
  - SIG_DFL表示使用默认方法处理
  - SIG_IGN表示忽略这个信号
  - function表示传入一个函数，用指定的函数处理
    - def function(sig, frame)
      
      sig：捕获到的信号
      
      frame：信号对象

View

  import signal
  from time import sleep
  
  signal.alarm(5)  # 5秒后向自身发送一个时钟信号
  # 使用信号的默认方法处理
  # signal.signal(signal.SIGALRM,signal.SIG_DFL)    
  # 忽略时钟信号
  # signal.signal(signal.SIGALRM,signal.SIG_IGN)
  # 忽略Ctrl+c信号
  # signal.signal(signal.SIGINT,signal.SIG_IGN)
  while True:
      sleep(2)
      print("等待时钟...")

View Code

  # 使用自定义函数处理信号
  import signal
  from time import sleep
  
  def fun1(sig, frame):
      if sig == signal.SIGALRM :
          print("接收到时钟信号")
      elif sig == signal.SIGINT :
          print("ctrl+c就不结束")
  
  signal.alarm(5)  # 5秒后向自身发送一个时钟信号
  # 使用自定义函数处理信号
  # 处理时钟信号
  signal.signal(signal.SIGALRM,fun1)    
  # 处理ctrl+c信号
  signal.signal(signal.SIGINT,fun1)
  
  while True:
      print("等待")
      sleep(2)
      
  '''打印结果
  等待
  等待
  等待
  接收到时钟信号
  等待
  ...
  '''

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信号量（信号灯）

原理：给定一个数量对多个进程可见，且多个进程都可以操作，进程可以对数量多少的判断执行各自的行为

from multiprocessing import Semaphore

sem = Semaphore(num)
- 功能：创建信号量
- 参数：信号量的初始值
- 返回值：信号量的对象
sem.get_value()：获取信号量的值
sem.acquire()：将信号量 -1，当信号为0时会阻塞
sem.release()：将信号量 +1

from multiprocessing import Semaphore, Process
# 创建信号量对象
sem = Semaphore(num)
def fun():
    print("进程%d等待信号量"%os.getpid())
    # 消耗一个信号量
    sem.acquire()
    print("进程%d消耗信号量"%os.getpid())
    # 添加一个信号量
    sem.release()
    print("进程%d添加信号量"%os.getpid())

jobs = []
for i in range(4):
    p = Process(target = 4)
    jobs.append(p)
    p.start()
for i in jobs:
    i.join()
print(sem.get_value())

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进程的同步互斥

临界资源：多个进程或者线程都能操作的共享资源

临界区：操作临界区资源的代码段

同步：同步是一种合作关系，为完成某个任务，多进程或者多线程之间形成的一种协调关系

互斥：互斥是一种制约关系，

Event事件

from multiprocessing import Event

e = Event()：创建一个事件对象
e.wait([timeout])：设置事件阻塞
e.set()：事件设置，当事件被设置后e.wait()不再阻塞，等于释放资源区
e.clear()：清除设置，当事件被设置e.clear()后，e.wait()又会阻塞，阻塞资源区
e.is_set()：事件状态判断，判断事件是否处于被设置的状态

from multiprocessing import Event
# 创建事件对象
e = Event()
# 查看
print(e.is_set())        # False
e.set()
print(e.is_set())        # True
e.wait(3)
print(e.is_set())        # True
e.clear()
print(e.is_set())        # False

View Code

from multiprocessing import Event,Process
from time import sleep

def wait_event1():
    print("1想操作临界区资源")
    e.wait()
    print("1开始操作临界区资源",e.is_set())
    with open("file") as f:
        print(f.read())
def wait_event2():
    print("2也想操作临界区资源")
    # 超时3秒检测
    e.wait(3)
    # 判断是否被设置
    if e.is_set():
        print("2开始操作临界区资源",e.is_set())
        with open("file") as f:
            print(f.read())
    else:
        print("2不能操作")       

# 创建事件对象
e = Event()
p1 = Process(target = wait_event1)
p2 = Process(target = wait_event2)
p1.start()
p2.start()
print("主进程操作")
with open("file",'w') as f:
    f.write("HELLO WORD")

# 延迟4秒释放临界区
sleep(4)
# 释放临界区资源
e.set()
print("释放临界区")
p1.join()
p2.join()

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Lock 锁

from multiprocessing import Lock

lock = Lock()：创建一个锁对象
lock.acquire()：上锁，如果已经是上锁状态，调用此函数会阻塞
lock.release()：解锁

from multiprocessing import Lock,Process
import sys
def writer1():
    # 上锁
    lock.acquire()
    for i in range(20):
        sys.stdout.write("writer1111\n")
    # 解锁
    lock.release() 
def writer2():
    # 上锁
    lock.acquire()
    for i in range(20):
        sys.stdout.write("writer2222\n")
    # 解锁
    lock.release()
lock = Lock()

w1 = Process(target = writer1)
w2 = Process(target = writer2)

w1.start()
w2.start()
w1.join()
w2.join()

View Code

第二种方法

使用with语句上锁，with语句执行完毕后会自动解

with lock:
    .....
    .....

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h2 tt,h2 code { font-size: inherit }
h3 tt,h3 code { font-size: inherit }
h4 tt,h4 code { font-size: inherit }
h5 tt,h5 code { font-size: inherit }
h6 tt,h6 code { font-size: inherit }
h1 { padding-bottom: 0.3em; font-size: 2.25em; line-height: 1.2; border-bottom: 1px solid rgb(238, 238, 238) }
h2 { padding-bottom: 0.3em; font-size: 1.75em; line-height: 1.225; border-bottom: 1px solid rgb(238, 238, 238) }
h3 { font-size: 1.5em; line-height: 1.43 }
h4 { font-size: 1.25em }
h5 { font-size: 1em }
h6 { font-size: 1em; color: rgb(119, 119, 119) }
p,blockquote,ul,ol,dl,table { margin: 0.8em 0px }
li>ol,li>ul { margin: 0px }
hr { height: 2px; padding: 0px; margin: 16px 0px; background-color: rgb(231, 231, 231); border: 0px none; overflow: hidden }
body>h2:first-child { margin-top: 0px; padding-top: 0px }
body>h1:first-child { margin-top: 0px; padding-top: 0px }
body>h1:first-child+h2 { margin-top: 0px; padding-top: 0px }
body>h3:first-child,body>h4:first-child,body>h5:first-child,body>h6:first-child { margin-top: 0px; padding-top: 0px }
a:first-child h1,a:first-child h2,a:first-child h3,a:first-child h4,a:first-child h5,a:first-child h6 { margin-top: 0px; padding-top: 0px }
h1 p,h2 p,h3 p,h4 p,h5 p,h6 p { margin-top: 0px }
li p.first { display: inline-block }
ul,ol { padding-left: 30px }
ul:first-child,ol:first-child { margin-top: 0px }
ul:last-child,ol:last-child { margin-bottom: 0px }
blockquote { border-left: 4px solid rgb(223, 226, 229); padding: 0px 15px; color: rgb(119, 119, 119) }
blockquote blockquote { padding-right: 0px }
table { padding: 0px }
table tr { border-top: 1px solid rgb(223, 226, 229); margin: 0px; padding: 0px }
table tr:nth-child(2n),thead { background-color: rgb(248, 248, 248) }
table tr th { font-weight: bold; border-width: 1px 1px 0px; border-top-style: solid; border-right-style: solid; border-left-style: solid; border-top-color: rgb(223, 226, 229); border-right-color: rgb(223, 226, 229); border-left-color: rgb(223, 226, 229); border-bottom-style: initial; border-bottom-color: initial; text-align: left; margin: 0px; padding: 6px 13px }
table tr td { border: 1px solid rgb(223, 226, 229); text-align: left; margin: 0px; padding: 6px 13px }
table tr th:first-child,table tr td:first-child { margin-top: 0px }
table tr th:last-child,table tr td:last-child { margin-bottom: 0px }
.CodeMirror-lines { padding-left: 4px }
.code-tooltip { border-top: 1px solid rgb(238, 242, 242) }
.md-fences,code,tt { border: 1px solid rgb(231, 234, 237); background-color: rgb(248, 248, 248); padding: 2px 4px 0px; font-size: 0.9em }
code { background-color: rgb(243, 244, 244); padding: 0px 4px 2px }
.md-fences { margin-bottom: 15px; margin-top: 15px; padding: 8px 1em 6px }
.md-task-list-item>input { margin-left: -1.3em }
.md-fences { background-color: rgb(248, 248, 248) }
#write pre.md-meta-block { padding: 1rem; font-size: 85%; line-height: 1.45; background-color: rgb(247, 247, 247); border: 0px; color: rgb(119, 119, 119); margin-top: 0px !important }
.mathjax-block>.code-tooltip { bottom: 0.375rem }
.md-mathjax-midline { background: rgb(250, 250, 250) }
#write>h3.md-focus::before { left: -1.5625rem; top: 0.375rem }
#write>h4.md-focus::before { left: -1.5625rem; top: 0.285714rem }
#write>h5.md-focus::before { left: -1.5625rem; top: 0.285714rem }
#write>h6.md-focus::before { left: -1.5625rem; top: 0.285714rem }
.md-image>.md-meta { padding: 2px 0px 0px 4px; font-size: 0.9em; color: inherit }
.md-tag { color: rgb(167, 167, 167); opacity: 1 }
.md-toc { margin-top: 20px; padding-bottom: 20px }
.sidebar-tabs { border-bottom: none }
#typora-quick-open { border: 1px solid rgb(221, 221, 221); background-color: rgb(248, 248, 248) }
#typora-quick-open-item { background-color: rgb(250, 250, 250); border-color: rgb(254, 254, 254) rgb(229, 229, 229) rgb(229, 229, 229) rgb(238, 238, 238); border-style: solid; border-width: 1px }
.on-focus-mode blockquote { border-left-color: rgba(85, 85, 85, 0.12) }
header,.context-menu,.megamenu-content,footer { font-family: “Segoe UI”, Arial, sans-serif }
.file-node-content:hover .file-node-icon,.file-node-content:hover .file-node-open-state { visibility: visible }
.mac-seamless-mode #typora-sidebar { background-color: var(–side-bar-bg-color) }
.md-lang { color: rgb(180, 101, 77) }
.html-for-mac .context-menu { }
.typora-export p,.typora-export .footnote-line { white-space: normal }

本文链接：https://www.cnblogs.com/BanL/p/9642216.html

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