LINUX multi-thread Learning (7)-implement "producer and consumer"

In the previous article, we used semaphores to achieve mutual exclusion between threads. This article uses the mutex synchronization mechanism of semaphores to implement a classic instance, that is, "producer and consumer ".

1. Briefly describe the problems of producers and consumers.

There is a buffer and two threads: producer and consumer. The producer places the product in the buffer zone, and the consumer removes the product from the buffer zone. When the buffer zone is full, the producer must wait. In addition, when the buffer zone is empty, the consumer must wait, and the buffer zone cannot operate both the producer and consumer.

# Include <stdio. h> <br/> # include <stdlib. h> <br/> # include <pthread. h> <br/> # include <semaphore. h> <br/> # include <errno. h> <br/> # include <fcntl. h> <br/> # include <string. h> </P> <p> # define FIFO "my_fifo" <br/> # define N 10 <br/> # define return_if_fail (p) if (P) = 0) {printf ("[% s]: func error! /N ", _ FUNC _); Return ;}</P> <p> typedef struct _ privinfo <br/>{< br/> sem_t avail; <br/> sem_t full; <br/> sem_t mutex; <br/> char buf_r [255]; <br/> time_t end_time; <br/> int FD; <br/>} privinfo; </P> <p> static void info_init (privinfo * thiz); <br/> static void info_destroy (privinfo * thiz ); <br/> static void * productor (privinfo * thiz); <br/> static void * Consumer (privinfo * thiz); </P> <p> int main (int Argc, char * argv []) <br/>{< br/> pthread_t pt_1 = 0; <br/> pthread_t pt_2 = 0; <br/> int ret = 0; <br/> privinfo * thiz = NULL; </P> <p> thiz = (privinfo *) malloc (sizeof (privinfo )); <br/> If (thiz = NULL) <br/> {<br/> printf ("[% s]: failed to malloc privinfo. /n ", _ FUNC _); <br/> return-1; <br/>}</P> <p> info_init (thiz ); </P> <p> ret = pthread_create (& pt_1, null, (void *) productor, thiz); <br /> If (Ret! = 0) <br/>{< br/> perror ("pthread_1_create:"); <br/>}</P> <p> ret = pthread_create (& pt_2, null, (void *) Consumer, thiz); <br/> If (Ret! = 0) <br/>{< br/> perror ("pthread_2_func:"); <br/>}</P> <p> pthread_join (pt_1, null ); <br/> pthread_join (pt_2, null); </P> <p> info_destroy (thiz); <br/> thiz = NULL; </P> <p> return 0; <br/>}</P> <p> static void info_init (privinfo * thiz) <br/>{< br/> return_if_fail (thiz! = NULL); </P> <p> thiz-> end_time = Time (null) + 10; </P> <p> sem_init (& thiz-> avail, 0, n); <br/> sem_init (& thiz-> full, 0, 0); <br/> sem_init (& thiz-> mutex, 0, 1 ); </P> <p> If (mkfifo (FIFO, o_creat | o_excl) & (errno! = Eexist) <br/>{< br/> printf ("cannot create FIFO server. /n "); <br/>}</P> <p> printf (" prepareing for reading bytes... /n "); </P> <p> memset (thiz-> buf_r, 0, sizeof (thiz-> buf_r )); </P> <p> thiz-> FD = open (FIFO, o_rdwr | o_nonblock, 0777); <br/> If (thiz-> FD =-1) <br/>{< br/> perror ("Open FIFO:"); <br/> info_destroy (thiz); <br/> exit (1 ); <br/>}</P> <p> return; <br/>}</P> <p> static void info _ Destroy (privinfo * thiz) <br/>{< br/> return_if_fail (thiz! = NULL); </P> <p> sem_destroy (& thiz-> avail); <br/> sem_destroy (& thiz-> full ); <br/> sem_destroy (& thiz-> mutex); </P> <p> free (thiz); <br/> thiz = NULL; </P> <p> return; <br/>}</P> <p> static void * productor (privinfo * thiz) <br/>{< br/> return_if_fail (thiz! = NULL); </P> <p> int ret = 0; </P> <p> while (Time (null) <thiz-> end_time) <br/>{< br/> sem_wait (& thiz-> avail); <br/> sem_wait (& thiz-> mutex ); </P> <p> If (ret = write (thiz-> FD, "hello", 5) =-1) <br/>{< br/> If (errno = eagain) <br/>{< br/> printf ("the FIFO has not been read, please try later again. /n "); <br/>}< br/> else <br/> {<br/> printf (" Write hello to the FIFO. /n "); <br/>}< br/>} </P> <p> sem_post (& thiz-> full); <br/> sem_post (& thiz-> mutex ); </P> <p> sleep (1); <br/>}</P> <p> return; <br/>}</P> <p> static void * Consumer (privinfo * thiz) <br/>{< br/> return_if_fail (thiz! = NULL); </P> <p> int ret = 0; </P> <p> while (Time (null) <thiz-> end_time) <br/>{< br/> sem_wait (& thiz-> full); <br/> sem_wait (& thiz-> mutex ); </P> <p> If (ret = read (thiz-> FD, thiz-> buf_r, 255)> 0) <br/>{</P> <p> printf ("read % s frm FIFO. /n ", thiz-> buf_r); <br/>}< br/> else <br/>{< br/> If (errno = eagain) <br/> {<br/> printf ("no data yet. /n "); <br/>}</P> <p> sem_post (& thiz-> avail ); <br/> sem_post (& thiz-> mutex); </P> <p> sleep (1); <br/>}</P> <p> return; <br/>}< br/>

From the classic example above, we have combined the multi-thread Simultaneous programming problem. The Learning thread has come to an end. In future programming applications, we hope to implement it in practice ~~