Linux interprocess communication-Semaphore __linux

* * Producer/consumer model * given warehouse volume (N) * Generator generated product warehousing * Consumers take out product consumption from warehouse * When the warehouse is full, the producer cannot continue to generate * The customer cannot continue to consume when the warehouse is empty * The access to the warehouse is exclusive * * Sembin Control exclusive access * Semmax Control warehouse Full * semmin Control warehouse Empty * * Producer consumer * p (Semmax) p (semmin) * p (Sembin) p (sembin) * (*product) + + (* Product)--Output Information * V (sembin) v (sembin) * V (semmin) v (semmax) * * * * * #include <stdio.h> #include <stdl ib.h> #include <sys/types.h> #include <unistd.h> #include <fcntl.h> #include <string.h> # Include <sys/mman.h> #include <semaphore.h> #include <assert.h> #include <signal.h> #define PC_ Shm_name "/PCSHM" #define Pc_sem_name_bin "/pcsembin" #define PC_SEM_NAME_MAX "/pcsemmax" #define PC_SEM_NAME_MIN "/p Csemmin "#define SHM_LENGTH 512//Shared memory length #define PRODUCT_MAX 30//Warehouse volume #ifndef FALSE #define FALSE 0 #endif #ifndef T	RUE #define TRUE 1 #endif int exitflag = 0;

Exit Flag * * CTRL + C signal/void Ctrlchandle (int signum) {exitflag = 1;} int main (void) {int * prodUct		Number of products, pointing to shared memory int shmfd;	Shared memory handle sem_t * SEMBIN;	Binary semaphore, control of warehouse uniqueness Access sem_t * SEMMAX;	Count semaphore, control product upper Limit sem_t * semmin;	Count semaphore, control product lower bound _bool Isfirst = FALSE;
	
	First run.
	
	Signal (SIGINT, ctrlchandle); Preparing shared memory Shmfd = Shm_open (pc_shm_name, O_RDWR | O_creat |
	O_EXCL, 0666);
		if (shmfd >= 0) {//create Isfirst = TRUE for the first time;
	Ftruncate (SHMFD, shm_length);
		}else {//re-open SHMFD = Shm_open (Pc_shm_name, O_RDWR, 0666);
			if (SHMFD < 0) {perror ("Shm_open");
		Exit (Exit_failure); }//Memory mapped product = (int *) mmap (NULL, Shm_length, prot_read|
	Prot_write, map_shared, SHMFD, 0);
		if (Product = = map_failed) {perror ("mmap");
		Shm_unlink (Pc_shm_name);
	Exit (Exit_failure);
	} if (Isfirst) {///first create shared memory, initialize *product = 0;
		//Open/Create semaphore if (isfirst) {sembin = Sem_open (Pc_sem_name_bin, O_creat, 0666, 1);
		Semmax = Sem_open (Pc_sem_name_max, O_creat, 0666, Product_max); Semmin = Sem_open (Pc_sem_name_min, O_cReat, 0666, 0);
		}else {sembin = Sem_open (pc_sem_name_bin, 0);
		Semmax = Sem_open (Pc_sem_name_max, 0);
	Semmin = Sem_open (pc_sem_name_min, 0);
		} if ((Sembin = = sem_failed) | |
		(Semmax = = sem_failed) | |
	(Semmin = = sem_failed))
		{perror ("Sem_open");
		Munmap (product, shm_length);
		Shm_unlink (Pc_shm_name);
	Exit (Exit_failure);
		}//main loop while (!exitflag) {#ifdef produce//producer//p (MAX) if (sem_wait (Semmax)!= 0) continue;
			P (BIN) if (sem_wait (Sembin)!= 0) {sem_post (Semmax);
		Continue
		///Production (*product) + +;
		printf ("produce:%d\n", *product);
		V (BIN) assert (Sem_post (sembin) = = 0);		
V (MIN) assert (Sem_post (semmin) = = 0);
		#else//Consumer//p (MIN) if (sem_wait (semmin)!= 0) continue;
			P (BIN) if (sem_wait (Sembin)!= 0) {sem_post (semmin);
		Continue
		//Consumption (*product)--;
		printf ("consume:%d\n", *product);
		V (BIN) assert (Sem_post (sembin) = = 0);
V (MAX) assert (Sem_post (semmax) = = 0); #endif UsleEP (100000);
	} munmap (product, shm_length);
	Shm_unlink (Pc_shm_name);
	Sem_close (Sembin);
	Sem_close (semmin);
	Sem_close (Semmax);
	Sem_unlink (Pc_sem_name_bin);
	Sem_unlink (pc_sem_name_min);
	
	Sem_unlink (Pc_sem_name_max);
return 0;
 }