证明线程确实共享内存

实践：

++x

Hello from thread 2
Hello from thread 7
Hello from thread 3
Hello from thread 4
Hello from thread 5
Hello from thread 6
Hello from thread 8
Hello from thread 9
Hello from thread B
Hello from thread A

x++

Hello from thread 1
Hello from thread 2
Hello from thread 3
Hello from thread 4
Hello from thread 5
Hello from thread 6
Hello from thread 7
Hello from thread 8
Hello from thread 9
Hello from thread A

多处理器编程：从入门到放弃 http://jyywiki.cn/OS/2022/slides/3.slides#/1/4

 

入门：thread.h 简化的线程 API

我们为大家封装了超级好用的线程 API (thread.h)

• create(fn)
  • 创建一个入口函数是 fn 的线程，并立即开始执行
    • void fn(int tid) { ... }
    • 参数 tid 从 1 开始编号
  • 语义：在状态中新增 stack frame 列表并初始化为 fn(tid)
• join()
  • 等待所有运行线程的 fn 返回
  • 在 main 返回时会自动等待所有线程结束
  • 语义：在有其他线程未执行完时死循环，否则返回
• 编译时需要增加 -lpthread

 

 

线程库 

thread.h

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdatomic.h>
#include <assert.h>
#include <unistd.h>
#include <pthread.h>

#define NTHREAD 64
enum { T_FREE = 0, T_LIVE, T_DEAD, };
struct thread {
  int id, status;
  pthread_t thread;
  void (*entry)(int);
};

struct thread tpool[NTHREAD], *tptr = tpool;

void *wrapper(void *arg) {
  struct thread *thread = (struct thread *)arg;
  thread->entry(thread->id);
  return NULL;
}

void create(void *fn) {
  assert(tptr - tpool < NTHREAD);
  *tptr = (struct thread) {
    .id = tptr - tpool + 1,
    .status = T_LIVE,
    .entry = fn,
  };
  pthread_create(&(tptr->thread), NULL, wrapper, tptr);
  ++tptr;
}

void join() {
  for (int i = 0; i < NTHREAD; i++) {
    struct thread *t = &tpool[i];
    if (t->status == T_LIVE) {
      pthread_join(t->thread, NULL);
      t->status = T_DEAD;
    }
  }
}

__attribute__((destructor)) void cleanup() {
  join();
}

　　

gcc   -lpthread

 

 

#include "thread.h"
void Ta(){while(1){printf("+++");}}
void Tb(){while(1){printf("___");}}
int main(){
    create(Ta);
    create(Tb);
}
// gcc multiThreaded.c -lpthread && ./a.out

 

 

#include "thread.h"
int x=0;
void Thello(int id){
    usleep(id*1000);
    printf("Hello from  thread %c\n","123456789ABCDEF"[x++]);
}
int main(){
    for(int i=0;i<10;i++){
        create(Thello);
    }
}