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From Dean Gaudet <dgau...@arctic.org>
Subject updated time-sem.c
Date Sun, 02 Nov 1997 00:53:52 GMT
This time-sem.c includes the necessary signal manipulations to allow us to
continue to use pthreads.  It appears to still be and order of magnitude
faster than fcntl locking.  I'm a little too busy to make a patch though,
so if someone could take the pthread code in time-sem.c here and compare
it against the server ... and generate a patch, that'd be great.  You also
have to properly release the mutex on any of the three unblocked signals --
which you should do in the handlers we already have for those signals,
so that we don't have to also instate a handler during the critical
section ...

For our known bugs in 1.3b2 we should probably list this, workaround is
to edit conf.h and switch to FCNTL locking.

Dean

/*
gcc -o time-FCNTL -Wall -O time-sem.c -DUSE_FCNTL_SERIALIZED_ACCEPT
gcc -o time-FLOCK -Wall -O time-sem.c -DUSE_FLOCK_SERIALIZED_ACCEPT
gcc -o time-SEM -Wall -O time-sem.c -DUSE_SYSVSEM_SERIALIZED_ACCEPT
gcc -o time-PTHREAD -Wall -O time-sem.c -DUSE_PTHREAD_SERIALIZED_ACCEPT -lpthread
*/

#include <errno.h>
#include <sys/time.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <sys/mman.h>
#include <signal.h>

#if defined(USE_FCNTL_SERIALIZED_ACCEPT)

static struct flock lock_it;
static struct flock unlock_it;

static int fcntl_fd=-1;

/*
 * Initialize mutex lock.
 * Must be safe to call this on a restart.
 */
void
accept_mutex_init(void)
{

    lock_it.l_whence = SEEK_SET;   /* from current point */
    lock_it.l_start  = 0;          /* -"- */
    lock_it.l_len    = 0;          /* until end of file */
    lock_it.l_type   = F_WRLCK;    /* set exclusive/write lock */
    lock_it.l_pid    = 0;          /* pid not actually interesting */
    unlock_it.l_whence = SEEK_SET; /* from current point */
    unlock_it.l_start  = 0;        /* -"- */
    unlock_it.l_len    = 0;        /* until end of file */
    unlock_it.l_type   = F_UNLCK;  /* set exclusive/write lock */
    unlock_it.l_pid    = 0;        /* pid not actually interesting */

    fcntl_fd = open("test-lock-thing", O_CREAT | O_WRONLY | O_EXCL, 0644);
    if (fcntl_fd == -1)
    {
	perror ("open");
	fprintf (stderr, "Cannot open lock file: %s\n", "test-lock-thing");
	exit (1);
    }
    unlink("test-lock-thing");
}

void accept_mutex_on(void)
{
    int ret;
    
    while ((ret = fcntl(fcntl_fd, F_SETLKW, &lock_it)) < 0 && errno == EINTR)
	continue;

    if (ret < 0) {
	perror ("fcntl lock_it");
	exit(1);
    }
}

void accept_mutex_off(void)
{
    if (fcntl (fcntl_fd, F_SETLKW, &unlock_it) < 0)
    {
	perror ("fcntl unlock_it");
	exit(1);
    }
}

#elif defined(USE_FLOCK_SERIALIZED_ACCEPT)

#include <sys/file.h>

static int flock_fd=-1;

/*
 * Initialize mutex lock.
 * Must be safe to call this on a restart.
 */
void
accept_mutex_init(void)
{

    flock_fd = open("test-lock-thing", O_CREAT | O_WRONLY | O_EXCL, 0644);
    if (flock_fd == -1)
    {
	perror ("open");
	fprintf (stderr, "Cannot open lock file: %s\n", "test-lock-thing");
	exit (1);
    }
    unlink("test-lock-thing");
}

void accept_mutex_on(void)
{
    int ret;
    
    while ((ret = flock(flock_fd, LOCK_EX)) < 0 && errno == EINTR)
	continue;

    if (ret < 0) {
	perror ("flock(LOCK_EX)");
	exit(1);
    }
}

void accept_mutex_off(void)
{
    if (flock (flock_fd, LOCK_UN) < 0)
    {
	perror ("flock(LOCK_UN)");
	exit(1);
    }
}

#elif defined (USE_SYSVSEM_SERIALIZED_ACCEPT)

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>

static   int sem_id = -1;

void accept_mutex_init(void)
{
          union semun {
               int val;
               struct semid_ds *buf;
               ushort *array;
          };

    union semun ick;

    sem_id = semget(999, 1, IPC_CREAT | 0666);
    if (sem_id < 0) {
       perror ("semget");
       exit (1);
    }
    ick.val = 1;
    if (semctl(sem_id, 0, SETVAL, ick) < 0) {
       perror ("semctl");
        exit(1);
    }
}

void accept_mutex_on()
{
    struct sembuf op;

    op.sem_num = 0;
    op.sem_op  = -1;
    op.sem_flg = SEM_UNDO;
    if (semop(sem_id, &op, 1) < 0) {
	perror ("accept_mutex_on");
	exit (1);
    }
}

void accept_mutex_off()
{
    struct sembuf op;

    op.sem_num = 0;
    op.sem_op  = 1;
    op.sem_flg = SEM_UNDO;
    if (semop(sem_id, &op, 1) < 0) {
	perror ("accept_mutex_off");
        exit (1);
    }
}

#elif defined (USE_PTHREAD_SERIALIZED_ACCEPT)

#include <pthread.h>

static pthread_mutex_t *mutex;
static sigset_t accept_block_mask;
static sigset_t accept_previous_mask;

void accept_mutex_init(void)
{
    pthread_mutexattr_t mattr;
    int fd;

    fd = open ("/dev/zero", O_RDWR);
    if (fd == -1) {
	perror ("open(/dev/zero)");
	exit (1);
    }
    mutex = (pthread_mutex_t *)mmap ((caddr_t)0, sizeof (*mutex),
		    PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
    if (mutex == (void *)(caddr_t)-1) {
	perror ("mmap");
	exit (1);
    }
    close (fd);
    if (pthread_mutexattr_init(&mattr)) {
	perror ("pthread_mutexattr_init");
	exit (1);
    }
    if (pthread_mutexattr_setpshared(&mattr, PTHREAD_PROCESS_SHARED)) {
	perror ("pthread_mutexattr_setpshared");
	exit (1);
    }
    if (pthread_mutex_init(mutex, &mattr)) {
	perror ("pthread_mutex_init");
	exit (1);
    }
    sigfillset(&accept_block_mask);
    sigdelset(&accept_block_mask, SIGHUP);
    sigdelset(&accept_block_mask, SIGTERM);
    sigdelset(&accept_block_mask, SIGUSR1);
}

void accept_mutex_on()
{
    if (sigprocmask(SIG_BLOCK, &accept_block_mask, &accept_previous_mask)) {
	perror("sigprocmask(SIG_BLOCK)");
	exit (1);
    }
    if (pthread_mutex_lock (mutex)) {
	perror ("pthread_mutex_lock");
	exit (1);
    }
}

void accept_mutex_off()
{
    if (pthread_mutex_unlock (mutex)) {
	perror ("pthread_mutex_unlock");
	exit (1);
    }
    if (sigprocmask(SIG_SETMASK, &accept_previous_mask, NULL)) {
	perror("sigprocmask(SIG_SETMASK)");
	exit (1);
    }
}

#elif defined (USE_USLOCK_SERIALIZED_ACCEPT)
#include <ulocks.h>
static usptr_t *us = NULL;
static ulock_t uslock = NULL;
void accept_mutex_init(void)
{
    ptrdiff_t old;
    /* default is 8 */
#define CONF_INITUSERS_MAX 15
    if ((old = usconfig(CONF_INITUSERS, CONF_INITUSERS_MAX)) == -1) {
        perror("usconfig");
        exit(-1);
    }
    if ((old = usconfig(CONF_LOCKTYPE, US_NODEBUG)) == -1) {
        perror("usconfig");
        exit(-1);
    }
    if ((old = usconfig(CONF_ARENATYPE, US_SHAREDONLY)) == -1) {
        perror("usconfig");
        exit(-1);
    }
    if ((us = usinit("/dev/zero")) == NULL) {
        perror("usinit");
        exit(-1);
    }
    if ((uslock = usnewlock(us)) == NULL) {
        perror("usnewlock");
        exit(-1);
    }
}
void accept_mutex_on()
{
    switch(ussetlock(uslock)) {
        case 1:
            /* got lock */
            break;
        case 0:
            fprintf(stderr, "didn't get lock\n");
            exit(-1);
        case -1:
            perror("ussetlock");
            exit(-1);
    }
}
void accept_mutex_off()
{
    if (usunsetlock(uslock) == -1) {
        perror("usunsetlock");
        exit(-1);
    }
}
#endif



void main (int argc, char **argv)
{
    int num_iter;
    int num_child;
    int i;
    struct timeval first;
    struct timeval last;
    long ms;
    int pid;
    unsigned long *shared_counter;

    if (argc != 3) {
	fprintf (stderr, "Usage: time-sem num-child num-iter\n");
	exit (1);
    }

    num_child = atoi (argv[1]);
    num_iter = atoi (argv[2]);

    /* allocate shared memory for the shared_counter */
    i = open ("/dev/zero", O_RDWR);
    if (i == -1) {
	perror ("open");
	exit (1);
    }
    shared_counter = (unsigned long *)mmap ((caddr_t)0,
		    sizeof (*shared_counter),
		    PROT_READ|PROT_WRITE, MAP_SHARED, i, 0);
    if (shared_counter == (void *)(caddr_t)-1) {
	perror ("mmap");
	exit (1);
    }
    close (i);

    /* initialize counter to 0 */
    *shared_counter = 0;

    accept_mutex_init ();

    /* parent grabs mutex until done spawning children */
    accept_mutex_on ();

    for (i = 0; i < num_child; ++i) {
	pid = fork();
	if (pid == 0) {
	    /* child, do our thing */
	    for (i = 0; i < num_iter; ++i) {
		accept_mutex_on ();
		++*shared_counter;
		accept_mutex_off ();
	    }
	    exit (0);
	} else if (pid == -1) {
	    perror ("fork");
	    exit (1);
	}
    }

    /* a quick test to see that nothing is screwed up */
    if (*shared_counter != 0) {
	puts ("WTF! shared_counter != 0 before the children have been started!");
	exit (1);
    }

    gettimeofday (&first, NULL);
    /* launch children into action */
    accept_mutex_off ();
    for (i = 0; i < num_child; ++i) {
	if (wait(NULL) == -1) {
	    perror ("wait");
	}
    }
    gettimeofday (&last, NULL);

    if (*shared_counter != num_child * num_iter) {
	puts ("WTF! shared_counter != num_child * num_iter!");
    }

    last.tv_sec -= first.tv_sec;
    ms = last.tv_usec - first.tv_usec;
    if (ms < 0) {
	--last.tv_sec;
	ms += 1000000;
    }
    last.tv_usec = ms;
    printf ("%8lu.%06lu\n", last.tv_sec, last.tv_usec);
}


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