// share is count of read accessors
// grant write lock when share == 0
-typedef struct {
- volatile unsigned char mutex; // 1 = busy
- volatile unsigned char write:1; // 1 = exclusive
- volatile unsigned char readwait:1; // readers are waiting
- volatile unsigned char writewait:1; // writers are waiting
- volatile unsigned char filler:5;
- volatile ushort share; // count of readers holding locks
- volatile ushort rcnt; // count of waiting readers
- volatile ushort wcnt; // count of waiting writers
+volatile typedef struct {
+ unsigned char mutex[1]; // 1 = busy
+ unsigned char write:1; // 1 = exclusive
+ unsigned char readwait:1; // readers are waiting
+ unsigned char writewait:1; // writers are waiting
+ unsigned char filler:5;
+ ushort share; // count of readers holding locks
+ ushort rcnt; // count of waiting readers
+ ushort wcnt; // count of waiting writers
} BtLatch;
// Define the length of the page and key pointers
uint min; // next key offset
unsigned char bits:7; // page size in bits
unsigned char free:1; // page is on free list
- unsigned char lvl:5; // level of page
+ unsigned char lvl:6; // level of page
unsigned char kill:1; // page is being deleted
unsigned char dirty:1; // page has deleted keys
- unsigned char posted:1; // page fence has posted
unsigned char right[BtId]; // page number to right
} *BtPage;
while( 1 ) {
// obtain latch mutex
- while( __sync_lock_test_and_set(&latch->mutex, 1) )
+ while( __sync_lock_test_and_set(latch->mutex, 1) )
sched_yield();
if( decr )
latch->readwait = 1;
latch->rcnt++;
prev = *(uint *)latch & ~1;
- __sync_lock_release (&latch->mutex);
+ __sync_lock_release (latch->mutex);
sys_futex( (uint *)latch, FUTEX_WAIT_BITSET | private, prev, NULL, NULL, QueRd );
decr = 1;
continue;
latch->readwait = 0;
latch->share++;
- __sync_lock_release (&latch->mutex);
+ __sync_lock_release (latch->mutex);
return;
}
}
while( 1 ) {
// obtain latch mutex
- while( __sync_lock_test_and_set(&latch->mutex, 1) )
+ while( __sync_lock_test_and_set(latch->mutex, 1) )
sched_yield();
if( decr )
latch->writewait = 1;
latch->wcnt++;
prev = *(uint *)latch & ~1;
- __sync_lock_release (&latch->mutex);
+ __sync_lock_release (latch->mutex);
sys_futex( (uint *)latch, FUTEX_WAIT_BITSET | private, prev, NULL, NULL, QueWr );
decr = 1;
continue;
latch->writewait = 0;
latch->write = 1;
- __sync_lock_release (&latch->mutex);
+ __sync_lock_release (latch->mutex);
return;
}
}
// try for mutex,
// abandon request if not taken
- if( __sync_lock_test_and_set(&latch->mutex, 1) )
+ if( __sync_lock_test_and_set(latch->mutex, 1) )
return 0;
// see if write mode is available
// release latch mutex
- __sync_lock_release (&latch->mutex);
+ __sync_lock_release (latch->mutex);
return ans;
}
// obtain latch mutex
- while( __sync_lock_test_and_set(&latch->mutex, 1) )
+ while( __sync_lock_test_and_set(latch->mutex, 1) )
sched_yield();
latch->write = 0;
// release latch mutex
wakexit:
- __sync_lock_release (&latch->mutex);
+ __sync_lock_release (latch->mutex);
}
// decrement reader count
// obtain latch mutex
- while( __sync_lock_test_and_set(&latch->mutex, 1) )
+ while( __sync_lock_test_and_set(latch->mutex, 1) )
sched_yield();
latch->share--;
- // wake waiting writers
+ // wake one waiting writer
if( !latch->share && latch->wcnt )
sys_futex( (uint *)latch, FUTEX_WAKE_BITSET | private, 1, NULL, NULL, QueWr );
// release latch mutex
- __sync_lock_release (&latch->mutex);
+ __sync_lock_release (latch->mutex);
}
// link latch table entry into latch hash table
BTERR bt_splitpage (BtDb *bt, BtPageSet *set)
{
uint cnt = 0, idx = 0, max, nxt = bt->mgr->page_size;
-unsigned char fencekey[256];
+unsigned char fencekey[256], rightkey[256];
uint lvl = set->page->lvl;
-uid right;
-BtKey key;
+BtPageSet right[1];
uint prev;
+BtKey key;
// split higher half of keys to bt->frame
slotptr(bt->frame, idx)->off = nxt;
}
+ // remember existing fence key for new page to the right
+
+ memcpy (rightkey, key, key->len + 1);
+
bt->frame->bits = bt->mgr->page_bits;
bt->frame->min = nxt;
bt->frame->cnt = idx;
// get new free page and write higher keys to it.
- if( !(right = bt_newpage(bt, bt->frame)) )
+ if( !(right->page_no = bt_newpage(bt, bt->frame)) )
return bt->err;
// update lower keys to continue in old page
memcpy (bt->frame, set->page, bt->mgr->page_size);
memset (set->page+1, 0, bt->mgr->page_size - sizeof(*set->page));
nxt = bt->mgr->page_size;
- set->page->posted = 0;
set->page->dirty = 0;
set->page->act = 0;
cnt = 0;
// remember fence key for smaller page
memcpy(fencekey, key, key->len + 1);
- bt_putid(set->page->right, right);
+
+ bt_putid(set->page->right, right->page_no);
set->page->min = nxt;
set->page->cnt = idx;
// if current page is the root page, split it
if( set->page_no == ROOT_page )
- return bt_splitroot (bt, set, fencekey, right);
-
- bt_unlockpage (BtLockWrite, set->latch);
- right = 0;
+ return bt_splitroot (bt, set, fencekey, right->page_no);
// insert new fences in their parent pages
- while( 1 ) {
- bt_lockpage (BtLockParent, set->latch);
- bt_lockpage (BtLockWrite, set->latch);
-
- key = keyptr (set->page, set->page->cnt);
- memcpy (fencekey, key, key->len + 1);
- prev = set->page->posted;
-
- if( right && prev ) {
- bt_unlockpage (BtLockParent, set->latch);
- bt_unlockpage (BtLockWrite, set->latch);
- bt_unpinlatch (set->latch);
- bt_unpinpool (set->pool);
- return 0;
- }
-
- right = bt_getid (set->page->right);
- set->page->posted = 1;
+ right->latch = bt_pinlatch (bt, right->page_no);
+ bt_lockpage (BtLockParent, right->latch);
- bt_unlockpage (BtLockWrite, set->latch);
+ bt_lockpage (BtLockParent, set->latch);
+ bt_unlockpage (BtLockWrite, set->latch);
- // insert new fence for reformulated left block of smaller keys
+ // insert new fence for reformulated left block of smaller keys
- if( !prev )
- if( bt_insertkey (bt, fencekey+1, *fencekey, lvl+1, set->page_no, time(NULL)) )
- return bt->err;
-
- bt_unlockpage (BtLockParent, set->latch);
- bt_unpinlatch (set->latch);
- bt_unpinpool (set->pool);
+ if( bt_insertkey (bt, fencekey+1, *fencekey, lvl+1, set->page_no, time(NULL)) )
+ return bt->err;
- if( !(set->page_no = right) )
- break;
+ // switch fence for right block of larger keys to new right page
- set->latch = bt_pinlatch (bt, right);
+ if( bt_insertkey (bt, rightkey+1, *rightkey, lvl+1, right->page_no, time(NULL)) )
+ return bt->err;
- if( set->pool = bt_pinpool (bt, right) )
- set->page = bt_page (bt, set->pool, right);
- else
- return bt->err;
- }
+ bt_unlockpage (BtLockParent, set->latch);
+ bt_unpinlatch (set->latch);
+ bt_unpinpool (set->pool);
+ bt_unlockpage (BtLockParent, right->latch);
+ bt_unpinlatch (right->latch);
return 0;
}
-
// Insert new key into the btree at given level.
BTERR bt_insertkey (BtDb *bt, unsigned char *key, uint len, uint lvl, uid id, uint tod)
projects / btree / blobdiff