-/*
- * Routine: lock_alloc
- * Function:
- * Allocate a lock for external users who cannot
- * hard-code the structure definition into their
- * objects.
- * For now just use kalloc, but a zone is probably
- * warranted.
- */
-lock_t *
-lock_alloc(
- boolean_t can_sleep,
- unsigned short tag,
- unsigned short tag1)
-{
- lock_t *l;
-
- if ((l = (lock_t *)kalloc(sizeof(lock_t))) != 0)
- lock_init(l, can_sleep, tag, tag1);
- return(l);
-}
-
-/*
- * Routine: lock_free
- * Function:
- * Free a lock allocated for external users.
- * For now just use kfree, but a zone is probably
- * warranted.
- */
-void
-lock_free(
- lock_t *l)
-{
- kfree(l, sizeof(lock_t));
-}
-
-
-/*
- * Routine: lock_init
- * Function:
- * Initialize a lock; required before use.
- * Note that clients declare the "struct lock"
- * variables and then initialize them, rather
- * than getting a new one from this module.
- */
-void
-lock_init(
- lock_t *l,
- boolean_t can_sleep,
- __unused unsigned short tag,
- unsigned short tag1)
-{
- (void) memset((void *) l, 0, sizeof(lock_t));
-
- simple_lock_init(&l->interlock, tag1);
- l->want_write = FALSE;
- l->want_upgrade = FALSE;
- l->read_count = 0;
- l->can_sleep = can_sleep;
-}
-
-
-/*
- * Sleep locks. These use the same data structure and algorithm
- * as the spin locks, but the process sleeps while it is waiting
- * for the lock. These work on uniprocessor systems.
- */
-
-#define DECREMENTER_TIMEOUT 1000000
-
-void
-lock_write(
- register lock_t * l)
-{
- register int i;
- boolean_t lock_miss = FALSE;
-#if MACH_LDEBUG
- int decrementer;
-#endif /* MACH_LDEBUG */
-
- simple_lock(&l->interlock);
-
-#if MACH_LDEBUG
- decrementer = DECREMENTER_TIMEOUT;
-#endif /* MACH_LDEBUG */
-
- /*
- * Try to acquire the want_write bit.
- */
- while (l->want_write) {
- if (!lock_miss) {
- lock_miss = TRUE;
- }
-
- i = lock_wait_time[l->can_sleep ? 1 : 0];
- if (i != 0) {
- simple_unlock(&l->interlock);
-#if MACH_LDEBUG
- if (!--decrementer)
- Debugger("timeout - want_write");
-#endif /* MACH_LDEBUG */
- while (--i != 0 && l->want_write)
- continue;
- simple_lock(&l->interlock);
- }
-
- if (l->can_sleep && l->want_write) {
- l->waiting = TRUE;
- thread_sleep_simple_lock((event_t) l,
- simple_lock_addr(l->interlock),
- THREAD_UNINT);
- /* interlock relocked */
- }
- }
- l->want_write = TRUE;
-
- /* Wait for readers (and upgrades) to finish */
-
-#if MACH_LDEBUG
- decrementer = DECREMENTER_TIMEOUT;
-#endif /* MACH_LDEBUG */
- while ((l->read_count != 0) || l->want_upgrade) {
- if (!lock_miss) {
- lock_miss = TRUE;
- }
-
- i = lock_wait_time[l->can_sleep ? 1 : 0];
- if (i != 0) {
- simple_unlock(&l->interlock);
-#if MACH_LDEBUG
- if (!--decrementer)
- Debugger("timeout - wait for readers");
-#endif /* MACH_LDEBUG */
- while (--i != 0 && (l->read_count != 0 ||
- l->want_upgrade))
- continue;
- simple_lock(&l->interlock);
- }
-
- if (l->can_sleep && (l->read_count != 0 || l->want_upgrade)) {
- l->waiting = TRUE;
- thread_sleep_simple_lock((event_t) l,
- simple_lock_addr(l->interlock),
- THREAD_UNINT);
- /* interlock relocked */
- }
- }
-
- simple_unlock(&l->interlock);
-}
-
-void
-lock_done(
- register lock_t * l)
-{
- boolean_t do_wakeup = FALSE;
-
-
- simple_lock(&l->interlock);
-
- if (l->read_count != 0) {
- l->read_count--;
- }
- else
- if (l->want_upgrade) {
- l->want_upgrade = FALSE;
- }
- else {
- l->want_write = FALSE;
- }
-
- /*
- * There is no reason to wakeup a waiting thread
- * if the read-count is non-zero. Consider:
- * we must be dropping a read lock
- * threads are waiting only if one wants a write lock
- * if there are still readers, they can't proceed
- */
-
- if (l->waiting && (l->read_count == 0)) {
- l->waiting = FALSE;
- do_wakeup = TRUE;
- }
-
- simple_unlock(&l->interlock);
-
- if (do_wakeup)
- thread_wakeup((event_t) l);
-}
-
-void
-lock_read(
- register lock_t * l)
-{
- register int i;
-#if MACH_LDEBUG
- int decrementer;
-#endif /* MACH_LDEBUG */
-
- simple_lock(&l->interlock);
-
-#if MACH_LDEBUG
- decrementer = DECREMENTER_TIMEOUT;
-#endif /* MACH_LDEBUG */
- while (l->want_write || l->want_upgrade) {
- i = lock_wait_time[l->can_sleep ? 1 : 0];
-
- if (i != 0) {
- simple_unlock(&l->interlock);
-#if MACH_LDEBUG
- if (!--decrementer)
- Debugger("timeout - wait no writers");
-#endif /* MACH_LDEBUG */
- while (--i != 0 && (l->want_write || l->want_upgrade))
- continue;
- simple_lock(&l->interlock);
- }
-
- if (l->can_sleep && (l->want_write || l->want_upgrade)) {
- l->waiting = TRUE;
- thread_sleep_simple_lock((event_t) l,
- simple_lock_addr(l->interlock),
- THREAD_UNINT);
- /* interlock relocked */
- }
- }
-
- l->read_count++;
-
- simple_unlock(&l->interlock);
-}
-
-
-/*
- * Routine: lock_read_to_write
- * Function:
- * Improves a read-only lock to one with
- * write permission. If another reader has
- * already requested an upgrade to a write lock,
- * no lock is held upon return.
- *
- * Returns TRUE if the upgrade *failed*.
- */
-
-boolean_t
-lock_read_to_write(
- register lock_t * l)
-{
- register int i;
- boolean_t do_wakeup = FALSE;
-#if MACH_LDEBUG
- int decrementer;
-#endif /* MACH_LDEBUG */
-
- simple_lock(&l->interlock);
-
- l->read_count--;
-
- if (l->want_upgrade) {
- /*
- * Someone else has requested upgrade.
- * Since we've released a read lock, wake
- * him up.
- */
- if (l->waiting && (l->read_count == 0)) {
- l->waiting = FALSE;
- do_wakeup = TRUE;
- }
-
- simple_unlock(&l->interlock);
-
- if (do_wakeup)
- thread_wakeup((event_t) l);
- return (TRUE);
- }
-
- l->want_upgrade = TRUE;
-
-#if MACH_LDEBUG
- decrementer = DECREMENTER_TIMEOUT;
-#endif /* MACH_LDEBUG */
- while (l->read_count != 0) {
- i = lock_wait_time[l->can_sleep ? 1 : 0];
-
- if (i != 0) {
- simple_unlock(&l->interlock);
-#if MACH_LDEBUG
- if (!--decrementer)
- Debugger("timeout - read_count");
-#endif /* MACH_LDEBUG */
- while (--i != 0 && l->read_count != 0)
- continue;
- simple_lock(&l->interlock);
- }
-
- if (l->can_sleep && l->read_count != 0) {
- l->waiting = TRUE;
- thread_sleep_simple_lock((event_t) l,
- simple_lock_addr(l->interlock),
- THREAD_UNINT);
- /* interlock relocked */
- }
- }
-
- simple_unlock(&l->interlock);
-
- return (FALSE);
-}
-
-void
-lock_write_to_read(
- register lock_t * l)
-{
- boolean_t do_wakeup = FALSE;
-
- simple_lock(&l->interlock);
-
- l->read_count++;
- if (l->want_upgrade)
- l->want_upgrade = FALSE;
- else
- l->want_write = FALSE;
-
- if (l->waiting) {
- l->waiting = FALSE;
- do_wakeup = TRUE;
- }
-
- simple_unlock(&l->interlock);
-
- if (do_wakeup)
- thread_wakeup((event_t) l);
-}
-
-
-#if 0 /* Unused */
-/*
- * Routine: lock_try_write
- * Function:
- * Tries to get a write lock.
- *
- * Returns FALSE if the lock is not held on return.
- */
-
-boolean_t
-lock_try_write(
- register lock_t * l)
-{
- pc_t pc;
-
- simple_lock(&l->interlock);
-
- if (l->want_write || l->want_upgrade || l->read_count) {
- /*
- * Can't get lock.
- */
- simple_unlock(&l->interlock);
- return(FALSE);
- }
-
- /*
- * Have lock.
- */
-
- l->want_write = TRUE;
-
- simple_unlock(&l->interlock);
-
- return(TRUE);
-}
-
-/*
- * Routine: lock_try_read
- * Function:
- * Tries to get a read lock.
- *
- * Returns FALSE if the lock is not held on return.
- */
-
-boolean_t
-lock_try_read(
- register lock_t * l)
-{
- pc_t pc;
-
- simple_lock(&l->interlock);
-
- if (l->want_write || l->want_upgrade) {
- simple_unlock(&l->interlock);
- return(FALSE);
- }
-
- l->read_count++;
-
- simple_unlock(&l->interlock);
-
- return(TRUE);
-}
-#endif /* Unused */
-
-
projects / apple / xnu.git / blobdiff