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1492. [cleanup] Preserve rwlock quota context when upgrading /

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downgrading. [RT #5599]
This commit is contained in:
Mark Andrews
2003-07-21 01:14:18 +00:00
parent afbb7b15ae
commit 17a14e451d
3 changed files with 22 additions and 6 deletions
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22
lib/isc/rwlock.c
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@@ -15,7 +15,7 @@
* WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/* $Id: rwlock.c,v 1.34 2003/04/17 01:56:34 marka Exp $ */
/* $Id: rwlock.c,v 1.35 2003/07/21 01:14:18 marka Exp $ */
#include <config.h>
@@ -82,6 +82,7 @@ isc_rwlock_init(isc_rwlock_t *rwl, unsigned int read_quota,
rwl->magic = 0;
rwl->type = isc_rwlocktype_read;
rwl->original = isc_rwlocktype_none;
rwl->active = 0;
rwl->granted = 0;
rwl->readers_waiting = 0;
@@ -215,9 +216,11 @@ isc_rwlock_tryupgrade(isc_rwlock_t *rwl) {
REQUIRE(rwl->active != 0);
/* If we are the only reader then succeed. */
if (rwl->active == 1)
if (rwl->active == 1) {
rwl->original = (rwl->original == isc_rwlocktype_none) ?
isc_rwlocktype_read : isc_rwlocktype_none;
rwl->type = isc_rwlocktype_write;
else
} else
result = ISC_R_LOCKBUSY;
UNLOCK(&rwl->lock);
@@ -233,10 +236,14 @@ isc_rwlock_downgrade(isc_rwlock_t *rwl) {
REQUIRE(rwl->active == 1);
rwl->type = isc_rwlocktype_read;
rwl->original = (rwl->original == isc_rwlocktype_none) ?
isc_rwlocktype_write : isc_rwlocktype_none;
/*
* Wake up waiting readers if there are no waiting writers.
* Resume processing any read request that were blocked when
* we upgraded.
*/
if ((rwl->writers_waiting == 0 || rwl->granted < rwl->read_quota) &&
if (rwl->original == isc_rwlocktype_none &&
(rwl->writers_waiting == 0 || rwl->granted < rwl->read_quota) &&
rwl->readers_waiting > 0)
BROADCAST(&rwl->readable);
@@ -260,6 +267,10 @@ isc_rwlock_unlock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
INSIST(rwl->active > 0);
rwl->active--;
if (rwl->active == 0) {
if (rwl->original != isc_rwlocktype_none) {
rwl->type = rwl->original;
rwl->original = isc_rwlocktype_none;
}
if (rwl->type == isc_rwlocktype_read) {
rwl->granted = 0;
if (rwl->writers_waiting > 0) {
@@ -287,6 +298,7 @@ isc_rwlock_unlock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
}
}
}
INSIST(rwl->original == isc_rwlock_none);
#ifdef ISC_RWLOCK_TRACE
print_lock(isc_msgcat_get(isc_msgcat, ISC_MSGSET_RWLOCK,