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1461. [bug] Remove deadlock from rbtdb code. [RT #5999]

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This commit is contained in:
Mark Andrews
2003-04-17 01:56:35 +00:00
parent 444d2ad833
commit 163547c0c0
4 changed files with 82 additions and 9 deletions
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66
lib/isc/rwlock.c
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@@ -15,7 +15,7 @@
* WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/* $Id: rwlock.c,v 1.33 2001/04/17 14:36:45 tale Exp $ */
/* $Id: rwlock.c,v 1.34 2003/04/17 01:56:34 marka Exp $ */
#include <config.h>
@@ -205,6 +205,44 @@ isc_rwlock_trylock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
return (doit(rwl, type, ISC_TRUE));
}
isc_result_t
isc_rwlock_tryupgrade(isc_rwlock_t *rwl) {
isc_result_t result = ISC_R_SUCCESS;
REQUIRE(VALID_RWLOCK(rwl));
LOCK(&rwl->lock);
REQUIRE(rwl->type == isc_rwlocktype_read);
REQUIRE(rwl->active != 0);
/* If we are the only reader then succeed. */
if (rwl->active == 1)
rwl->type = isc_rwlocktype_write;
else
result = ISC_R_LOCKBUSY;
UNLOCK(&rwl->lock);
return (result);
}
void
isc_rwlock_downgrade(isc_rwlock_t *rwl) {
REQUIRE(VALID_RWLOCK(rwl));
LOCK(&rwl->lock);
REQUIRE(rwl->type == isc_rwlocktype_write);
REQUIRE(rwl->active == 1);
rwl->type = isc_rwlocktype_read;
/*
* Wake up waiting readers if there are no waiting writers.
*/
if ((rwl->writers_waiting == 0 || rwl->granted < rwl->read_quota) &&
rwl->readers_waiting > 0)
BROADCAST(&rwl->readable);
UNLOCK(&rwl->lock);
}
isc_result_t
isc_rwlock_unlock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
@@ -318,6 +356,32 @@ isc_rwlock_trylock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
return (isc_rwlock_lock(rwl, type));
}
isc_result_t
isc_rwlock_tryupgrade(isc_rwlock_t *rwl) {
isc_result_t result = ISC_R_SUCCESS;
REQUIRE(VALID_RWLOCK(rwl));
REQUIRE(rwl->type == isc_rwlocktype_read);
REQUIRE(rwl->active != 0);
/* If we are the only reader then succeed. */
if (rwl->active == 1)
rwl->type = isc_rwlocktype_write;
else
result = ISC_R_LOCKBUSY;
return (result);
}
void
isc_rwlock_downgrade(isc_rwlock_t *rwl) {
REQUIRE(VALID_RWLOCK(rwl));
REQUIRE(rwl->type == isc_rwlocktype_write);
REQUIRE(rwl->active == 1);
rwl->type = isc_rwlocktype_read;
}
isc_result_t
isc_rwlock_unlock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
REQUIRE(VALID_RWLOCK(rwl));