P296 18.3 线程存在的问题和临界区

ch18/README.md

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+18.

ch18/thread1.c

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+#include <stdio.h>
+#include <pthread.h>
+#include <unistd.h>
+void *thread_main(void *arg);
+
+int main(int argc, char *argv[])
+{
+    pthread_t t_id;
+    int thread_param = 5;
+    // 请求创建一个线程，从 thread_main 调用开始，在单独的执行流中运行。同时传递参数
+    if (pthread_create(&t_id, NULL, thread_main, (void *)&thread_param) != 0)
+    {
+        puts("pthread_create() error");
+        return -1;
+    }
+    sleep(10); //延迟进程终止时间
+    puts("end of main");
+    return 0;
+}
+void *thread_main(void *arg) //传入的参数是 pthread_create 的第四个
+{
+    int i;
+    int cnt = *((int *)arg);
+    for (int i = 0; i < cnt; i++)
+    {
+        sleep(1);
+        puts("running thread");
+    }
+    return NULL;
+}

ch18/thread2.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <pthread.h>
+void *thread_main(void *arg);
+
+int main(int argc, char *argv[])
+{
+    pthread_t t_id;
+    int thread_param = 5;
+    void *thr_ret;
+    // 请求创建一个线程，从 thread_main 调用开始，在单独的执行流中运行。同时传递参数
+    if (pthread_create(&t_id, NULL, thread_main, (void *)&thread_param) != 0)
+    {
+        puts("pthread_create() error");
+        return -1;
+    }
+    //main函数将等待 ID 保存在 t_id 变量中的线程终止
+    if (pthread_join(t_id, &thr_ret) != 0)
+    {
+        puts("pthread_join() error");
+        return -1;
+    }
+    printf("Thread return message : %s \n", (char *)thr_ret);
+    free(thr_ret);
+    return 0;
+}
+void *thread_main(void *arg) //传入的参数是 pthread_create 的第四个
+{
+    int i;
+    int cnt = *((int *)arg);
+    char *msg = (char *)malloc(sizeof(char) * 50);
+    strcpy(msg, "Hello,I'am thread~ \n");
+    for (int i = 0; i < cnt; i++)
+    {
+        sleep(1);
+        puts("running thread");
+    }
+    return (void *)msg; //返回值是 thread_main 函数中内部动态分配的内存空间地址值
+}

ch18/thread3.c

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+#include <stdio.h>
+#include <pthread.h>
+void *thread_summation(void *arg);
+int sum = 0;
+
+int main(int argc, char *argv[])
+{
+    pthread_t id_t1, id_t2;
+    int range1[] = {1, 5};
+    int range2[] = {6, 10};
+
+    pthread_create(&id_t1, NULL, thread_summation, (void *)range1);
+    pthread_create(&id_t2, NULL, thread_summation, (void *)range2);
+
+    pthread_join(id_t1, NULL);
+    pthread_join(id_t2, NULL);
+    printf("result: %d \n", sum);
+    return 0;
+}
+void *thread_summation(void *arg)
+{
+    int start = ((int *)arg)[0];
+    int end = ((int *)arg)[1];
+    while (start <= end)
+    {
+        sum += start;
+        start++;
+    }
+    return NULL;
+}

ch18/thread4.c

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+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <pthread.h>
+#define NUM_THREAD 100
+
+void *thread_inc(void *arg);
+void *thread_des(void *arg);
+long long num = 0;
+
+int main(int argc, char *argv[])
+{
+    pthread_t thread_id[NUM_THREAD];
+    int i;
+
+    printf("sizeof long long: %d \n", sizeof(long long));
+    for (i = 0; i < NUM_THREAD; i++)
+    {
+        if (i % 2)
+            pthread_create(&(thread_id[i]), NULL, thread_inc, NULL);
+        else
+            pthread_create(&(thread_id[i]), NULL, thread_des, NULL);
+    }
+
+    for (i = 0; i < NUM_THREAD; i++)
+        pthread_join(thread_id[i], NULL);
+
+    printf("result: %lld \n", num);
+    return 0;
+}
+
+void *thread_inc(void *arg)
+{
+    int i;
+    for (i = 0; i < 50000000; i++)
+        num += 1;
+    return NULL;
+}
+void *thread_des(void *arg)
+{
+    int i;
+    for (i = 0; i < 50000000; i++)
+        num -= 1;
+    return NULL;
+}