Description
Do the following for this assignment: 1. Add necessary synchronization code in the following C++ programs to correct problems due to race condition, and compile them into executables shmp3 and shmc3, respectively. Make sure that sufficient and proper comments are included on the added code as well as the existing code. 2. Run your corrected version of shmp3 (with shmc3) to make sure that the output is correct. 3. Submit on BeachBoard the two corrected programs, along with the booking3.h file, a screenshot that shows successful compile of both programs as well as a successful run, and a cover page that provides your name, your student ID, course # and section, assignment #, due date, submission date, and a clear program description detailing what you have done for the correction. Format of the cover page should follow the cover page template on BeachBoard. 4. The programs must be properly formatted and adequately commented to enhance readability and understanding. Detailed documentation on all system calls are especially needed. /* booking3.h * Header file to be used with * shmp3.cpp and shmc3.cpp */ #include // header file needed for POSIX semaphore struct TOUR { char bus_number[6]; char date[9]; char title[50]; int seats_left; }; struct BUS { sem_t sem1; // semaphore to control access to tour data below TOUR tour1 = { “4321”, “11262021”, “Grand Canyon Tour”, 20 }; } mybus; /* shmp3.cpp */ #include “booking3.h” #include <sys/types.h> #include <sys/ipc.h> #include <sys/shm.h> #include <sys/wait.h> #include #include #include #include #include using namespace std; #define NCHILD 3 int shm_init( void * ); void wait_and_wrap_up( int [], void *, int ); void rpterror( char *, char * ); int main(int argc, char *argv[]) { int child[NCHILD], i, shmid; void *shm_ptr; char ascshmid[10], pname[14]; shmid = shm_init(shm_ptr); sprintf (ascshmid, “%d”, shmid); cout << “Bus ” << mybus.tour1.bus_number << ” for ” << mybus.tour1.title << ” on ” << mybus.tour1.date << “, ” << mybus.tour1.seats_left << ” seats available. ” << endl; cout << “Booking begins: ” << endl << endl; for (i = 0; i < NCHILD; i++) { child[i] = fork(); switch (child[i]) { case -1: sprintf (pname, “child%d”, i+1); rpterror ((char *)”fork failed”, pname); exit(1); case 0: sprintf (pname, “shmc%d”, i+1); execl(“shmc3″, pname, ascshmid, (char *)0); rpterror ((char *)”execl failed”, pname); exit (2); } } wait_and_wrap_up (child, shm_ptr, shmid); } int shm_init(void *shm_ptr) { int shmid; shmid = shmget(ftok(“.”,’u’), sizeof(BUS), 0600 | IPC_CREAT); if (shmid == -1) { perror (“shmget failed”); exit(3); } shm_ptr = shmat(shmid, (void * ) 0, 0); if (shm_ptr == (void *) -1) { perror (“shmat failed”); exit(4); } memcpy (shm_ptr, (void *) &mybus, sizeof(BUS) ); return (shmid); } void wait_and_wrap_up(int child[], void *shm_ptr, int shmid) { int wait_rtn, w, ch_active = NCHILD; while (ch_active > 0) { wait_rtn = wait( (int *)0 ); for (w = 0; w < NCHILD; w++) if (child[w] == wait_rtn) { ch_active–; break; } } cout << “Parent removing shm” << endl; shmdt (shm_ptr); shmctl (shmid, IPC_RMID, (struct shmid_ds *) 0); exit (0); } void rpterror(char *string, char *pname) { char errline[50]; sprintf (errline, “%s %s”, string, pname); perror (errline); } /* shmc3.cpp */ #include “booking3.h” #include <sys/types.h> #include <sys/ipc.h> #include <sys/shm.h> #include <sys/wait.h> #include #include #include #include #include using namespace std; BUS *bus_ptr; void *memptr; char *pname; int shmid, ret; void rpterror(char *), srand(), perror(), sleep(); void sell_seats(); int main(int argc, char* argv[]) { if (argc < 2) { fprintf (stderr, “Usage:, %s shmid\n”, argv[0]); exit(1); } pname = argv[0]; sscanf (argv[1], “%d”, &shmid); memptr = shmat (shmid, (void *)0, 0); if (memptr == (char *)-1 ) { rpterror ((char *)”shmat failed”); exit(2); } bus_ptr = (struct BUS *)memptr; sell_seats(); ret = shmdt(memptr); exit(0); } void sell_seats() { int all_out = 0; srand ( (unsigned) getpid() ); while ( !all_out) { /* loop to sell all seats */ if (bus_ptr->tour1.seats_left > 0) { sleep ( (unsigned)rand()%2 + 1); bus_ptr->tour1.seats_left–; sleep ( (unsigned)rand()%5 + 1); cout << pname << ” SOLD SEAT — ” << bus_ptr->tour1.seats_left << ” left” << endl; } else { all_out++; cout << pname << ” sees no seats left” << endl; } sleep ( (unsigned)rand()%5 + 1); } } void rpterror(char* string) { char errline[50]; sprintf (errline, “%s %s”, string, pname); perror (errline); }
