/** Create a new semaphore.
* @param name Optional name for the semaphore, for debugging purposes.
* @param count Initial count of the semaphore.
* @param security Security attributes for the ACL. If NULL, default
* attributes will be constructed which grant full access
* to the semaphore to the calling process' user.
* @param rights Access rights for the handle.
* @param handlep Where to store handle to the semaphore.
* @return Status code describing result of the operation. */
status_t kern_semaphore_create(const char *name, size_t count,
const object_security_t *security, object_rights_t rights,
handle_t *handlep)
{
object_security_t ksecurity = { -1, -1, NULL };
user_semaphore_t *sem;
status_t ret;
if(!handlep)
return STATUS_INVALID_ARG;
if(security) {
ret = object_security_from_user(&ksecurity, security, true);
if(ret != STATUS_SUCCESS)
return ret;
}
/* Construct a default ACL if required. */
if(!ksecurity.acl) {
ksecurity.acl = kmalloc(sizeof(*ksecurity.acl), MM_WAIT);
object_acl_init(ksecurity.acl);
object_acl_add_entry(ksecurity.acl, ACL_ENTRY_USER, -1, SEMAPHORE_RIGHT_USAGE);
}
sem = kmalloc(sizeof(user_semaphore_t), MM_WAIT);
sem->id = id_allocator_alloc(&semaphore_id_allocator);
if(sem->id < 0) {
kfree(sem);
object_security_destroy(&ksecurity);
return STATUS_NO_SEMAPHORES;
}
if(name) {
ret = strndup_from_user(name, SEMAPHORE_NAME_MAX, &sem->name);
if(ret != STATUS_SUCCESS) {
id_allocator_free(&semaphore_id_allocator, sem->id);
kfree(sem);
object_security_destroy(&ksecurity);
return ret;
}
} else {
sem->name = NULL;
}
object_init(&sem->obj, &semaphore_object_type, &ksecurity, NULL);
object_security_destroy(&ksecurity);
semaphore_init(&sem->sem, (sem->name) ? sem->name : "user_semaphore", count);
refcount_set(&sem->count, 1);
rwlock_write_lock(&semaphore_tree_lock);
avl_tree_insert(&semaphore_tree, &sem->tree_link, sem->id, sem);
rwlock_unlock(&semaphore_tree_lock);
ret = object_handle_create(&sem->obj, NULL, rights, NULL, 0, NULL, NULL, handlep);
if(ret != STATUS_SUCCESS)
user_semaphore_release(sem);
return ret;
}
/** Release a user semaphore.
* @param sem Semaphore to release. */
static void user_semaphore_release(user_semaphore_t *sem) {
if(refcount_dec(&sem->count) == 0) {
rwlock_write_lock(&semaphore_tree_lock);
avl_tree_remove(&semaphore_tree, &sem->tree_link);
rwlock_unlock(&semaphore_tree_lock);
object_destroy(&sem->obj);
id_allocator_free(&semaphore_id_allocator, sem->id);
kfree(sem);
}
}
/*
* REQUIRES:
* block write lock
*
* EFFECTS:
* empower the fly holes to be visiable
*/
void block_shrink(struct block *b)
{
uint32_t i, j;
rwlock_write_lock(&b->rwlock, &b->mtx);
for (i = 0, j = 0; i < b->pairs_used; i++) {
if (b->pairs[i].used) {
b->pairs[j++] = b->pairs[i];
}
}
b->pairs_used = j;
rwlock_write_unlock(&b->rwlock);
}
void block_init(struct block *b,
struct block_pair *pairs,
uint32_t n)
{
uint32_t i;
nassert(n > 0);
rwlock_write_lock(&b->rwlock, &b->mtx);
qsort(pairs, n, sizeof(*pairs), _pair_compare_fun);
for (i = 0; i < n; i++) {
_extend(b, 1);
memcpy(&b->pairs[i], &pairs[i], sizeof(*pairs));
b->pairs_used++;
}
/* get the last allocated postion of file*/
b->allocated += pairs[n - 1].offset;
b->allocated += ALIGN(pairs[n - 1].real_size);
rwlock_write_unlock(&b->rwlock);
}
DISKOFF block_alloc_off(struct block *b,
uint64_t nid,
uint32_t real_size,
uint32_t skeleton_size,
uint32_t height)
{
DISKOFF r;
uint32_t i;
int found = 0;
uint32_t pos = 0;
rwlock_write_lock(&b->rwlock, &b->mtx);
r = ALIGN(b->allocated);
_extend(b, 1);
/*
* set old hole to fly
* it is not visible until you call 'block_shrink'
*/
for (i = 0; i < b->pairs_used; i++) {
if (b->pairs[i].nid == nid) {
b->pairs[i].used = 0;
break;
}
}
/* find the not-fly hole to reuse */
if (b->pairs_used > 0) {
for (pos = 0; pos < (b->pairs_used - 1); pos++) {
DISKOFF off_aligned;
struct block_pair *p;
struct block_pair *nxtp;
p = &b->pairs[pos];
nxtp = &b->pairs[pos + 1];
off_aligned = (ALIGN(p->offset) + ALIGN(p->real_size));
if ((off_aligned + ALIGN(real_size)) <= nxtp->offset) {
r = off_aligned;
memmove(&b->pairs[pos + 1 + 1],
&b->pairs[pos + 1],
sizeof(*b->pairs) * (b->pairs_used - pos - 1));
found = 1;
break;
}
}
}
/* found the reuse hole */
if (found) {
pos += 1;
} else {
pos = b->pairs_used;
b->allocated = (ALIGN(b->allocated) + ALIGN(real_size));
}
b->pairs[pos].offset = r;
b->pairs[pos].height = height;
b->pairs[pos].real_size = real_size;
b->pairs[pos].skeleton_size = skeleton_size;
b->pairs[pos].nid = nid;
b->pairs[pos].used = 1;
b->pairs_used++;
rwlock_write_unlock(&b->rwlock);
return r;
}
int
main(void)
{
uint64_t s_b, e_b, i;
ck_bytelock_t bytelock = CK_BYTELOCK_INITIALIZER;
rwlock_t naive;
for (i = 0; i < STEPS; i++) {
ck_bytelock_write_lock(&bytelock, 1);
ck_bytelock_write_unlock(&bytelock);
}
s_b = rdtsc();
for (i = 0; i < STEPS; i++) {
ck_bytelock_write_lock(&bytelock, 1);
ck_bytelock_write_unlock(&bytelock);
}
e_b = rdtsc();
printf("WRITE: bytelock %15" PRIu64 "\n", (e_b - s_b) / STEPS);
rwlock_init(&naive);
for (i = 0; i < STEPS; i++) {
rwlock_write_lock(&naive);
rwlock_write_unlock(&naive);
}
s_b = rdtsc();
for (i = 0; i < STEPS; i++) {
rwlock_write_lock(&naive);
rwlock_write_unlock(&naive);
}
e_b = rdtsc();
printf("WRITE: naive %15" PRIu64 "\n", (e_b - s_b) / STEPS);
for (i = 0; i < STEPS; i++) {
ck_bytelock_read_lock(&bytelock, 1);
ck_bytelock_read_unlock(&bytelock, 1);
}
s_b = rdtsc();
for (i = 0; i < STEPS; i++) {
ck_bytelock_read_lock(&bytelock, 1);
ck_bytelock_read_unlock(&bytelock, 1);
}
e_b = rdtsc();
printf("READ: bytelock %15" PRIu64 "\n", (e_b - s_b) / STEPS);
for (i = 0; i < STEPS; i++) {
rwlock_read_lock(&naive);
rwlock_read_unlock(&naive);
}
s_b = rdtsc();
for (i = 0; i < STEPS; i++) {
rwlock_read_lock(&naive);
rwlock_read_unlock(&naive);
}
e_b = rdtsc();
printf("READ: naive %15" PRIu64 "\n", (e_b - s_b) / STEPS);
return (0);
}