A small example of process synchronization problem in Linux __linux

The following code allocates space to the memory file using Mmap, and uses fork to generate a parent-child process that synchronizes and deadlocks through the semaphore in Semaphore. Completes the synchronization of the parent-child process.

#include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <semaphore.h> #include <
sys/mman.h> int* count = 0;
sem_t *mutex1 = NULL;
sem_t *mutex2 = NULL;
int finish = 0; int main () {mutex1 = (sem_t*) mmap (NULL, sizeof (sem_t), prot_read| Prot_write, map_anon|
    Map_shared,-1, 0); Mutex2 = (sem_t*) mmap (NULL, sizeof (sem_t), prot_read| Prot_write, map_anon|
    Map_shared,-1, 0); Count = (int*) mmap (null,sizeof (int), prot_read| Prot_write, map_anon|
    Map_shared, -1,0);
    Sem_init (MUTEX1, 1, 1);
    Sem_init (mutex2, 1, 0);
    *count = 0;
            if (fork () ==0) {while (1) {printf ("Child continue!\n");
            Sem_wait (MUTEX1);
            *count + 2;
            printf ("child:%d\n", *count);
            finish++;
            Sem_post (MUTEX2);
        if (finish = = ten) break;
        printf ("Child finish!\n");
    Exit (0);
while (1) {printf ("Father continue!\n");        Sem_wait (MUTEX2);
        *count-= 1;
        printf ("father:%d\n", *count);
        finish++;
        Sem_post (MUTEX1);
    if (finish = = ten) break;
    } Sem_destroy (MUTEX1);
    Sem_destroy (MUTEX2);
    Munmap (mutex1, sizeof (sem_t));
    Munmap (mutex2, sizeof (sem_t));
    Munmap (count, sizeof (int));
    printf ("Finished all!\n");
return 0;
 }

Compiling under Linux

[Root@localhost myfile]# gcc testsem.c-  o testsem-lpthread

Run Result:

[Root@localhost myfile]#./testsem 
Father continue!
Child continue!
Child:2 Child
continue!
Father:1
Father continue!
Child:3 Child
continue!
Father:2
Father continue!
Child:4 Child
continue!
Father:3
Father continue!
Child:5 Child
continue!
Father:4
Father continue!
Child:6 Child
continue!
Father:5
Father continue!
Child:7 Child
continue!
Father:6
Father continue!
Child:8 Child
continue!
Father:7
Father continue!
Child:9 Child
continue!
Father:8
Father continue!
Child:10 Child
continue!
Father:9
Father continue!
Child:11 Child
finish!
Father:10
finished all!