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-rw-r--r--CS3871/sync/assign.rst41
-rw-r--r--CS3871/sync/makefile5
-rw-r--r--CS3871/sync/reader.c86
-rw-r--r--CS3871/sync/sync.c118
-rw-r--r--CS3871/sync/writer.c76
5 files changed, 326 insertions, 0 deletions
diff --git a/CS3871/sync/assign.rst b/CS3871/sync/assign.rst
new file mode 100644
index 0000000..ea4a566
--- /dev/null
+++ b/CS3871/sync/assign.rst
@@ -0,0 +1,41 @@
+================
+Syncronization 1
+================
+
+Write a program that uses semaphores to implement a readers/writers solution. Your program should:
+
+ - be written in C and use the standard kernel IPC mechanisms (semget,semop,shmget etc)
+ - be written as a single top level source file compiled as: gcc –o myprog myprog.c
+ - take two arguments on the command line: myprog NR NW where NR,NW are each integers specifying the number of reader/writer processes respectively
+ - use fork/exec to create the readers/writers
+
+The shared memory segment should be 16k bytes in size, with all bytes initialized to 0x30
+
+Reader:
+
+.. code ::
+
+ open a file (for append) named reader.N, where N is the reader number
+ while (1) {
+ for (i=0; i<16k; i++) {
+ read the next byte of the shared memory segment
+ write that byte to the file
+ flush the file
+ }
+ sleep a random number of seconds, between 0 and N inclusive
+ }
+
+Writer:
+
+.. code ::
+
+ while (1) {
+ for (i=0; i<16k; i++)
+ shared memory segment[i] = N + 0x30;
+ sleep a random number of seconds between 0 and 2*N inclusive
+ }
+
+readers and writers should be mutually exclusive
+multiple concurrent readers are allowed
+writers have priority over readers
+writers are mutually exclusive relative to each other
diff --git a/CS3871/sync/makefile b/CS3871/sync/makefile
new file mode 100644
index 0000000..dd9c463
--- /dev/null
+++ b/CS3871/sync/makefile
@@ -0,0 +1,5 @@
+sync: sync.c reader.c writer.c
+ cc -o sync sync.c
+ cc -o reader reader.c
+ cc -o writer writer.c
+
diff --git a/CS3871/sync/reader.c b/CS3871/sync/reader.c
new file mode 100644
index 0000000..929eba1
--- /dev/null
+++ b/CS3871/sync/reader.c
@@ -0,0 +1,86 @@
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#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)
+int signum;
+{
+ shmdt(mem);
+ exit(1);
+}
+
+int main(argc, argv)
+int argc;
+char **argv;
+{
+ int shmid, semid, i, pid, id;
+ char filename[50];
+ FILE *fd;
+ struct sembuf sb;
+
+ if (argc < 2) {
+ printf("usage: reader [id]\n");
+ exit(1);
+ }
+
+ id = atoi(argv[1]);
+
+
+ if ((shmid = shmget(52, 1<<14, IPC_CREAT | 0666)) == -1){
+ perror("shmget: shmget failed");
+ exit(1);
+ }
+
+ if ((mem = shmat(shmid, NULL, 0)) == (char *) -1) {
+ perror("shmat");
+ exit(1);
+ }
+
+ if ((semid = semget(shmid, NSEM, 0)) == -1) {
+ perror("Rsemget: ");
+ exit(1);
+ }
+
+ signal(SIGQUIT, quit);
+
+ sprintf(filename, "reader.%d", id);
+
+ fd = fopen(filename, "a");
+
+ if (!fd) {
+ perror("fopen: ");
+ exit(1);
+ }
+ srand(time(NULL));
+
+ while (1) {
+ 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);
+ }
+ fprintf(fd, "\n");
+ fflush(fd);
+
+ sb.sem_op = 1;
+ semop(semid, &sb, 1);
+
+
+ sleep(rand() % (id + 1));
+ }
+}
diff --git a/CS3871/sync/sync.c b/CS3871/sync/sync.c
new file mode 100644
index 0000000..23d6ba1
--- /dev/null
+++ b/CS3871/sync/sync.c
@@ -0,0 +1,118 @@
+#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);
+}
+
+
+int main(argc, argv)
+int argc;
+char **argv;
+{
+ 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");
+ exit(1);
+ }
+ n_read = atoi(argv[1]);
+ n_write = atoi(argv[2]);
+
+ if ((shmid = shmget(52, 1<<14, IPC_CREAT | 0666)) == -1){
+ perror("shmget: shmget failed");
+ exit(1);
+ }
+
+ if ((mem = shmat(shmid, NULL, 0)) == (char *) -1) {
+ perror("shmat");
+ exit(1);
+ }
+printf("Sshmid: %x\n", shmid);
+ signal(SIGQUIT, quit);
+
+ 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);
+ *arg_w = malloc(sizeof(char) * 10);
+
+ *(arg_r + 1) = malloc(sizeof(char) * 50);
+ *(arg_w + 1) = malloc(sizeof(char) * 50);
+
+ *arg_r = "reader";
+ *arg_w = "writer";
+
+ *(arg_r + 2) = NULL;
+ *(arg_w + 2) = NULL;
+
+ for (i = 0; i < n_read; i++){
+ sprintf(*(arg_r + 1), "%d", i);
+ if (pid = fork()) {
+ /* printf("starting reader %d...\n", i); */
+ } else {
+ int ret = execv("./reader", arg_r);
+ printf("exec retern %d", ret);
+ }
+ }
+
+ for (i = 0; i < n_write; i++) {
+ sprintf(*(arg_w + 1), "%d", i);
+ if (pid = fork()) {
+ /* printf("starting writer %d...\n", i); */
+ } else {
+ execvp("./writer", arg_w);
+ }
+
+ }
+
+ shmdt(mem);
+printf("sync done...\n");
+/* TODO
+ * why is this returning 8
+ */
+ for (i = 0; i < (n_write + n_read); i++) {
+ wait(&w);
+ printf("\nReturned with code:%d\n", WEXITSTATUS(w));
+ }
+ quit();
+}
diff --git a/CS3871/sync/writer.c b/CS3871/sync/writer.c
new file mode 100644
index 0000000..d38dd70
--- /dev/null
+++ b/CS3871/sync/writer.c
@@ -0,0 +1,76 @@
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#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)
+int signum;
+{
+ shmdt(mem);
+ exit(1);
+}
+
+int main(argc, argv)
+int argc;
+char **argv;
+{
+ int shmid, semid, i, pid, id;
+ char *mem;
+ struct sembuf sb;
+
+ if (argc < 2) {
+ printf("usage: writer [id]\n");
+ exit(1);
+ }
+
+ id = atoi(argv[1]);
+
+
+ if ((shmid = shmget(52, 1<<14, IPC_CREAT | 0666)) == -1){
+ perror("shmget: shmget failed");
+ exit(1);
+ }
+
+ if ((mem = shmat(shmid, NULL, 0)) == (char *) -1) {
+ perror("shmat");
+ exit(1);
+ }
+printf("Wshmid: %x\n", shmid);
+
+ if ((semid = semget(shmid, NSEM, 0)) == -1) {
+ perror("Wsemget: ");
+ exit(1);
+ }
+
+ signal(SIGQUIT, quit);
+
+ srand(time(NULL));
+
+ while (1) {
+ rand() % 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;
+ }
+
+ sb.sem_op = 1;
+ semop(semid, &sb, 1);
+
+ sleep(rand() % ((id * 2) + 1));
+ }
+}
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