fifo.3源代码:系统调用读写操作的方式以及线程无法工作的原因?
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <limits.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <pthread.h>
#include <time.h>
#define FIFO_NAME "/tmp/my_fifo"
#define BUFFER_SIZE PIPE_BUF //4096
#define TEN_MEG (1024 * 1024 * 1)
void* thread_tick(void* arg)
{
int count =0;
while(count < 4){
printf("hello, world!\n");
sleep(1);
count++;
}
}
void* thread_write(void* arg)
{
int pipe_fd;
int res;
int bytes_sent = 0;
char buffer[BUFFER_SIZE ];
int count=0;
if (access(FIFO_NAME, F_OK) == -1) {
res = mkfifo(FIFO_NAME, 0777);
if (res != 0) {
fprintf(stderr, "Could not create fifo %s\n", FIFO_NAME);
exit(EXIT_FAILURE);
}
}
while(count < 10){
printf("write: Process %d opening FIFO O_WRONLY\n", getpid());
pipe_fd = open(FIFO_NAME, O_WRONLY);
printf("write: Process %d result %d \n", getpid(), pipe_fd);
if (pipe_fd != -1) {
while(bytes_sent < TEN_MEG) {
res = write(pipe_fd, buffer, BUFFER_SIZE);
if (res == -1) {
fprintf(stderr, "Write error on pipe\n");
exit(EXIT_FAILURE);
}
bytes_sent += res;
}
(void)close(pipe_fd);
}
else {
exit(EXIT_FAILURE);
}
printf("write: Process %d finished , count =%d\n", getpid(),count);
count++;
}
}
void CreateThread(void* (*start_routine)(void*), void* arg,int stacksize, int priority)
{
pthread_t app_thread;
pthread_attr_t thread_attr;
int res;
int max_priority;
int min_priority;
struct sched_param scheduling_value;
res = pthread_attr_init(&thread_attr);
if (res != 0) {
perror("Attribute creation failed\n");
exit(EXIT_FAILURE);
}
res = pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_DETACHED);
if (res != 0) {
perror("Setting detached attribute failed");
exit(EXIT_FAILURE);
}
res = pthread_attr_setstacksize(&thread_attr, stacksize);
if (res != 0) {
perror("Set stack size failed\n");
exit(EXIT_FAILURE);
}
res = pthread_attr_setschedpolicy(&thread_attr, SCHED_RR);
if (res != 0) {
perror("Setting schedpolicy failed");
exit(EXIT_FAILURE);
}
max_priority = sched_get_priority_max(SCHED_RR);
min_priority = sched_get_priority_min(SCHED_RR);
scheduling_value.sched_priority = priority;
res = pthread_attr_setschedparam(&thread_attr, &scheduling_value);
if (res != 0) {
perror("Setting schedpolicy failed");
exit(EXIT_FAILURE);
}
res = pthread_create(&app_thread, &thread_attr, (*start_routine), arg);
if(res != 0){
perror("Thread creation failed\n");
exit(EXIT_FAILURE);
}
pthread_attr_destroy(&thread_attr);
//res = pthread_join(app_thread ,0);
//return app_thread;
}
int main()
{
CreateThread(thread_write, 0, 50000, 99);
CreateThread(thread_tick, 0, 50000, 98);
// pthread_join(w,0);
// pthread_join(t ,0);
return 0;
}
fifo.4源代码:
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <limits.h>
#include <sys/types.h>
#include <sys/stat.h>
#define FIFO_NAME "/tmp/my_fifo"
#define BUFFER_SIZE PIPE_BUF //4096
int main()
{
int pipe_fd;
int res;
char buffer[BUFFER_SIZE ];
int bytes_read = 0;
int count = 0;
memset(buffer, '\0', sizeof(buffer));
while(count < 10){
printf("read: Process %d opening FIFO O_RDONLY\n", getpid());
pipe_fd = open(FIFO_NAME, O_RDONLY);
printf("read: Process %d result %d\n", getpid(), pipe_fd);
if (pipe_fd != -1) {
do {
res = read(pipe_fd, buffer, BUFFER_SIZE);
bytes_read += res;
} while (res > 0);
(void)close(pipe_fd);
}
else {
exit(EXIT_FAILURE);
}
printf("read: Process %d finished, %d bytes read , count =%d\n", getpid(), bytes_read,count);
count++;
}
return 0;
}
这是我第一次张贴在堆栈溢出代码,因此它是一个烂摊子。 以上是两个C源代码。 fifo3.c有两个线程,thread_write是将数据写入到命名的fifo。 012ofifo4.c是从命名的fifo读取数据。
我的问题:
1)如何读(pipe_fd,缓冲,BUFFER_SIZE)时,write()方法将数据写入FIFO的行为?如果read()不能读取数据,不应该读取()返回0,然后退出,为什么read()会等待write()来完成写入数据?当然,read()读取时write()如何表现?
2)在fifo3.c中,我创建了两个线程,当我创建它们分离时,程序无法运行! 但可以连接,它们可以正确运行!!我不知道为什么!理论上,它们都可以正常运作。
的问题-1
对于问题1,如果read()将阻止等待数据到达,它何时会退出,它将如何知道它正在等待的数据将会到达还是不会永远到达,然后决定继续等待还是退出?到问题2,如果在程序中有三个进程,并且每个都创建了几个希望无限运行的线程,我应该使用可连接属性创建它们吗? – city 2012-03-10 11:14:58
'fcntl',而不是'ioctl',能够转换到非阻塞模式。 – 2012-03-10 12:34:28
@R,谢谢。已编辑和更新。 :) – Jay 2012-03-12 04:28:01