CS3871/assignments/sync: Added basic semaphore solution (no concurent readers)

	P(sem)
	  crit
	V(sem)

Removed debugging prints

3 files changed, 69 insertions, 22 deletions

diff --git a/sync/reader.c b/sync/reader.c
index 66ee57b..929eba1 100644
--- a/sync/reader.c
+++ b/sync/reader.c
@@ -4,11 +4,15 @@
 #include <stdlib.h>
 #include <sys/ipc.h>
 #include <sys/select.h>
+#include <sys/sem.h>
 #include <sys/shm.h>
 #include <sys/types.h>
 #include <time.h>
 #include <unistd.h>
 
+#define NSEM 3
+#define KEY 52
+
 char *mem;
 
 void quit(signum)
@@ -22,10 +26,10 @@ int main(argc, argv)
 int argc;
 char **argv;
 {
-printf("\tR STARTING\n");
-	int shmid, i, pid, id;
+	int shmid, semid, i, pid, id;
 	char filename[50];
 	FILE *fd;
+	struct sembuf sb;
 
 	if (argc < 2) {
 		printf("usage: reader [id]\n");
@@ -33,7 +37,6 @@ printf("\tR STARTING\n");
 	}
 
 	id = atoi(argv[1]);
-printf("\tR%d. started...\n", id);
 
 
 	if ((shmid = shmget(52, 1<<14, IPC_CREAT | 0666)) == -1){
@@ -45,12 +48,16 @@ printf("\tR%d. started...\n", id);
 		perror("shmat");
 		exit(1);
 	}
+
+	if ((semid = semget(shmid, NSEM, 0)) == -1) {
+		perror("Rsemget: ");
+		exit(1);
+	}
+
 	signal(SIGQUIT, quit);
-printf("\tR%d. SHMID: %d\n", id, shmid);
 
 	sprintf(filename, "reader.%d", id);
 	
-printf("\tR%d. opening file \"%s\"...\n", id, filename);
 	fd = fopen(filename, "a");
 
 	if (!fd) {
@@ -60,7 +67,9 @@ printf("\tR%d. opening file \"%s\"...\n", id, filename);
 	srand(time(NULL));
 
 	while (1) {
-printf("\tR%d. reading...\n", id);
+		sb.sem_num = 0; sb.sem_op = -1; sb.sem_flg = 0;
+		semop(semid, &sb, 1);
+
 		for (i = 0; i < 1<<14; i++) {
 			fprintf(fd, "%c", *(mem + i));
 			fflush(fd);
@@ -68,7 +77,10 @@ printf("\tR%d. reading...\n", id);
 		fprintf(fd, "\n");
 		fflush(fd);
 
-printf("\tR%d. waiting...\n", id);
+		sb.sem_op = 1;
+		semop(semid, &sb, 1);
+
+
 		sleep(rand() % (id + 1));
 	}
 }
diff --git a/sync/sync.c b/sync/sync.c
index 66574a1..23d6ba1 100644
--- a/sync/sync.c
+++ b/sync/sync.c
@@ -1,15 +1,28 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/ipc.h>
+#include <sys/sem.h>
 #include <sys/shm.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>
 
+#define NSEM 3
+
+union semun {
+	int val;
+	struct semid_ds *buf;
+	ushort *array;
+};
+
+
+int shmid, semid;
+
 void quit(signum)
 int signum;
 {
 	shmctl(shmid, IPC_RMID, NULL);
+	semctl(semid, IPC_RMID, 0);
 }
 
 
@@ -17,8 +30,9 @@ int main(argc, argv)
 int argc;
 char **argv;
 {
-	int shmid, i, pid, n_read, n_write, w;
+	int i, pid, n_read, n_write, w;
 	char *mem, **arg_r, **arg_w;
+	union semun semarg;
 
 	if (argc < 2) {
 		printf("usage: sync [number readers] [number writers]\n");
@@ -36,13 +50,27 @@ char **argv;
 		perror("shmat");
 		exit(1);
 	}
+printf("Sshmid: %x\n", shmid);
 	signal(SIGQUIT, quit);
 
-printf("\nSHMID: %d\nsetting initial memory values...\n", shmid);
 	for (i = 0; i < 1<<14; i++) {
 		*(mem + i) = 0x30;
 	}
 
+	if ((semid = semget(shmid, NSEM, 0666 | IPC_CREAT)) == -1) {
+		perror("Ssemget: ");
+		exit(1);
+	}
+
+	semarg.val = 1;
+	for (i = 0; i < NSEM; i++) {
+		if ((semctl(semid, i, SETVAL, semarg)) == -1) {
+			perror("semctl: ");
+			exit(1);
+		}
+	}
+
+
 	arg_r = malloc(sizeof(char*) * 3);
 	arg_w = malloc(sizeof(char*) * 3);
 	*arg_r = malloc(sizeof(char) * 10);
@@ -57,11 +85,8 @@ printf("\nSHMID: %d\nsetting initial memory values...\n", shmid);
 	*(arg_r + 2) = NULL;
 	*(arg_w + 2) = NULL;
 
-printf("forking readers...\n");
 	for (i = 0; i < n_read; i++){
-printf("sprintf...\n");
 		sprintf(*(arg_r + 1), "%d", i);
-printf("\t%d\n",i);
 		if (pid = fork()) {
 			/* printf("starting reader %d...\n", i); */
 		} else {
@@ -70,10 +95,8 @@ printf("\t%d\n",i);
 		}
 	}
 
-printf("forking writers...\n");
 	for (i = 0; i < n_write; i++) {
 		sprintf(*(arg_w + 1), "%d", i);
-printf("\t%d\n", i);
 		if (pid = fork()) {
 			/* printf("starting writer %d...\n", i); */
 		} else {
@@ -89,7 +112,7 @@ printf("sync done...\n");
  */
 	for (i = 0; i < (n_write + n_read); i++) {
 		wait(&w);
-		printf("\nReturned with code:%d\n", WTERMSIG(w));
+		printf("\nReturned with code:%d\n", WEXITSTATUS(w));
 	}
 	quit();
 }
diff --git a/sync/writer.c b/sync/writer.c
index b1ab9ed..d38dd70 100644
--- a/sync/writer.c
+++ b/sync/writer.c
@@ -4,12 +4,15 @@
 #include <stdlib.h>
 #include <sys/ipc.h>
 #include <sys/select.h>
+#include <sys/sem.h>
 #include <sys/shm.h>
 #include <sys/types.h>
 #include <sys/types.h>
 #include <time.h>
 #include <unistd.h>
 
+#define NSEM 3
+
 char *mem;
 
 void quit(signum)
@@ -23,9 +26,9 @@ int main(argc, argv)
 int argc;
 char **argv;
 {
-printf("\tW STARTING\n");
-	int shmid, i, pid, id;
+	int shmid, semid, i, pid, id;
 	char *mem;
+	struct sembuf sb;
 
 	if (argc < 2) {
 		printf("usage: writer [id]\n");
@@ -34,7 +37,6 @@ printf("\tW STARTING\n");
 
 	id = atoi(argv[1]);
 
-printf("\tW%d. started...\n", id);
 
 	if ((shmid = shmget(52, 1<<14, IPC_CREAT | 0666)) == -1){
 		perror("shmget: shmget failed");
@@ -45,20 +47,30 @@ printf("\tW%d. started...\n", id);
 		perror("shmat");
 		exit(1);
 	}
+printf("Wshmid: %x\n", shmid);
+
+	if ((semid = semget(shmid, NSEM, 0)) == -1) {
+		perror("Wsemget: ");
+		exit(1);
+	}
 
 	signal(SIGQUIT, quit);
-printf("\tW%d. SHMID: %d\n", id, shmid);
 	
 	srand(time(NULL));
 
 	while (1) {
-printf("\tW%d. testing...\n", id);
 		rand() % id;
-printf("\tW%d. writing...\n", id);
+		
+		sb.sem_num = 0; sb.sem_op = -1; sb.sem_flg = 0;
+		semop(semid, &sb, 1);
+
 		for (i = 0; i < 1<<14; i++) {
 			mem[i]= 0x30 + id;
 		}
-printf("\tW%d. waiting...\n");
+		
+		sb.sem_op = 1;
+		semop(semid, &sb, 1);
+
 		sleep(rand() % ((id * 2) + 1));
 	}
 }