Remove isc_rwlock_downgrade() from isc_rwlock

The isc_rwlock_downgrade() is not used anywhere, so we can remove it and
make the pthread_rwlock implementation simpler.

diff --git a/lib/isc/include/isc/rwlock.h b/lib/isc/include/isc/rwlock.h
index 30bdd85763c81d114fd2e375d7580a5e6e965954..68b91fc2b4723c61ce0bef699f371b52caa34313 100644 (file)
--- a/lib/isc/include/isc/rwlock.h
+++ b/lib/isc/include/isc/rwlock.h
@@ -35,15 +35,10 @@ typedef enum {
 #if USE_PTHREAD_RWLOCK
 #include <pthread.h>
 
-struct isc_rwlock {
-       pthread_rwlock_t rwlock;
-       atomic_bool      downgrade;
-};
-
 #if ISC_TRACK_PTHREADS_OBJECTS
 
-typedef struct isc_rwlock *isc_rwlock_t;
-typedef struct isc_rwlock  isc__rwlock_t;
+typedef pthread_rwlock_t *isc_rwlock_t;
+typedef pthread_rwlock_t  isc__rwlock_t;
 
 #define isc_rwlock_init(rwl, rq, wq)            \
        {                                       \
@@ -54,7 +49,6 @@ typedef struct isc_rwlock  isc__rwlock_t;
 #define isc_rwlock_trylock(rwl, type) isc___rwlock_trylock(*rwl, type)
 #define isc_rwlock_unlock(rwl, type)  isc__rwlock_unlock(*rwl, type)
 #define isc_rwlock_tryupgrade(rwl)    isc___rwlock_tryupgrade(*rwl)
-#define isc_rwlock_downgrade(rwl)     isc__rwlock_downgrade(*rwl)
 #define isc_rwlock_destroy(rwl)             \
        {                                   \
                isc___rwlock_destroy(*rwl); \
@@ -63,15 +57,14 @@ typedef struct isc_rwlock  isc__rwlock_t;
 
 #else /* ISC_TRACK_PTHREADS_OBJECTS */
 
-typedef struct isc_rwlock isc_rwlock_t;
-typedef struct isc_rwlock isc__rwlock_t;
+typedef pthread_rwlock_t isc_rwlock_t;
+typedef pthread_rwlock_t isc__rwlock_t;
 
 #define isc_rwlock_init(rwl, rq, wq)  isc__rwlock_init(rwl, rq, wq)
 #define isc_rwlock_lock(rwl, type)    isc__rwlock_lock(rwl, type)
 #define isc_rwlock_trylock(rwl, type) isc___rwlock_trylock(rwl, type)
 #define isc_rwlock_unlock(rwl, type)  isc__rwlock_unlock(rwl, type)
 #define isc_rwlock_tryupgrade(rwl)    isc___rwlock_tryupgrade(rwl)
-#define isc_rwlock_downgrade(rwl)     isc__rwlock_downgrade(rwl)
 #define isc_rwlock_destroy(rwl)              isc__rwlock_destroy(rwl)
 
 #endif /* ISC_TRACK_PTHREADS_OBJECTS */
@@ -122,7 +115,6 @@ typedef struct isc_rwlock isc__rwlock_t;
 #define isc_rwlock_trylock(rwl, type) isc___rwlock_trylock(rwl, type)
 #define isc_rwlock_unlock(rwl, type)  isc__rwlock_unlock(rwl, type)
 #define isc_rwlock_tryupgrade(rwl)    isc___rwlock_tryupgrade(rwl)
-#define isc_rwlock_downgrade(rwl)     isc__rwlock_downgrade(rwl)
 #define isc_rwlock_destroy(rwl)              isc__rwlock_destroy(rwl)
 
 #endif /* USE_PTHREAD_RWLOCK */
@@ -145,12 +137,6 @@ typedef struct isc_rwlock isc__rwlock_t;
                PTHREADS_RUNTIME_CHECK(isc___rwlock_unlock, _ret); \
        }
 
-#define isc__rwlock_downgrade(rwl)                                    \
-       {                                                             \
-               int _ret = isc___rwlock_downgrade(rwl);               \
-               PTHREADS_RUNTIME_CHECK(isc___rwlock_downgrade, _ret); \
-       }
-
 #define isc__rwlock_destroy(rwl)                                    \
        {                                                           \
                int _ret = isc___rwlock_destroy(rwl);               \
@@ -173,9 +159,6 @@ isc___rwlock_unlock(isc__rwlock_t *rwl, isc_rwlocktype_t type);
 isc_result_t
 isc___rwlock_tryupgrade(isc__rwlock_t *rwl);
 
-int
-isc___rwlock_downgrade(isc__rwlock_t *rwl);
-
 int
 isc___rwlock_destroy(isc__rwlock_t *rwl);
 

diff --git a/lib/isc/rwlock.c b/lib/isc/rwlock.c
index 8f1956e5c4e36c9ea27a36a01b1b095411a28aaf..739f9746b03ba27fb0b8f5c728519746b2d8f398 100644 (file)
--- a/lib/isc/rwlock.c
+++ b/lib/isc/rwlock.c
@@ -39,39 +39,18 @@ isc___rwlock_init(isc__rwlock_t *rwl, unsigned int read_quota,
        UNUSED(read_quota);
        UNUSED(write_quota);
 
-       ret = pthread_rwlock_init(&rwl->rwlock, NULL);
-
-       atomic_init(&rwl->downgrade, false);
+       ret = pthread_rwlock_init(rwl, NULL);
 
        return (ret);
 }
 
 int
 isc___rwlock_lock(isc__rwlock_t *rwl, isc_rwlocktype_t type) {
-       int ret;
-
        switch (type) {
        case isc_rwlocktype_read:
-               return (pthread_rwlock_rdlock(&rwl->rwlock));
+               return (pthread_rwlock_rdlock(rwl));
        case isc_rwlocktype_write:
-               while (true) {
-                       ret = pthread_rwlock_wrlock(&rwl->rwlock);
-                       if (ret != 0) {
-                               return (ret);
-                       }
-                       /* Unlock if in middle of downgrade operation */
-                       if (atomic_load_acquire(&rwl->downgrade)) {
-                               ret = pthread_rwlock_unlock(&rwl->rwlock);
-                               if (ret != 0) {
-                                       return (ret);
-                               }
-                               while (atomic_load_acquire(&rwl->downgrade)) {
-                               }
-                               continue;
-                       }
-                       break;
-               }
-               return (0);
+               return (pthread_rwlock_wrlock(rwl));
        default:
                UNREACHABLE();
        }
@@ -82,14 +61,10 @@ isc___rwlock_trylock(isc__rwlock_t *rwl, isc_rwlocktype_t type) {
        int ret = 0;
        switch (type) {
        case isc_rwlocktype_read:
-               ret = pthread_rwlock_tryrdlock(&rwl->rwlock);
+               ret = pthread_rwlock_tryrdlock(rwl);
                break;
        case isc_rwlocktype_write:
-               ret = pthread_rwlock_trywrlock(&rwl->rwlock);
-               if ((ret == 0) && atomic_load_acquire(&rwl->downgrade)) {
-                       RUNTIME_CHECK(pthread_rwlock_unlock(&rwl->rwlock) == 0);
-                       return (ISC_R_LOCKBUSY);
-               }
+               ret = pthread_rwlock_trywrlock(rwl);
                break;
        default:
                UNREACHABLE();
@@ -110,7 +85,7 @@ isc___rwlock_trylock(isc__rwlock_t *rwl, isc_rwlocktype_t type) {
 int
 isc___rwlock_unlock(isc__rwlock_t *rwl, isc_rwlocktype_t type) {
        UNUSED(type);
-       return (pthread_rwlock_unlock(&rwl->rwlock));
+       return (pthread_rwlock_unlock(rwl));
 }
 
 isc_result_t
@@ -119,30 +94,9 @@ isc___rwlock_tryupgrade(isc__rwlock_t *rwl) {
        return (ISC_R_LOCKBUSY);
 }
 
-int
-isc___rwlock_downgrade(isc__rwlock_t *rwl) {
-       int ret;
-
-       atomic_store_release(&rwl->downgrade, true);
-
-       ret = pthread_rwlock_unlock(&rwl->rwlock);
-       if (ret != 0) {
-               return (ret);
-       }
-
-       ret = pthread_rwlock_rdlock(&rwl->rwlock);
-       if (ret != 0) {
-               return (ret);
-       }
-
-       atomic_store_release(&rwl->downgrade, false);
-
-       return (0);
-}
-
 int
 isc___rwlock_destroy(isc__rwlock_t *rwl) {
-       return (pthread_rwlock_destroy(&rwl->rwlock));
+       return (pthread_rwlock_destroy(rwl));
 }
 
 #else /* if USE_PTHREAD_RWLOCK */
@@ -555,32 +509,6 @@ isc___rwlock_tryupgrade(isc__rwlock_t *rwl) {
        return (ISC_R_SUCCESS);
 }
 
-int
-isc___rwlock_downgrade(isc__rwlock_t *rwl) {
-       int32_t prev_readers;
-
-       REQUIRE(VALID_RWLOCK(rwl));
-
-       /* Become an active reader. */
-       prev_readers = atomic_fetch_add_release(&rwl->cnt_and_flag,
-                                               READER_INCR);
-       /* We must have been a writer. */
-       INSIST((prev_readers & WRITER_ACTIVE) != 0);
-
-       /* Complete write */
-       atomic_fetch_sub_release(&rwl->cnt_and_flag, WRITER_ACTIVE);
-       atomic_fetch_add_release(&rwl->write_completions, 1);
-
-       /* Resume other readers */
-       LOCK(&rwl->lock);
-       if (rwl->readers_waiting > 0) {
-               BROADCAST(&rwl->readable);
-       }
-       UNLOCK(&rwl->lock);
-
-       return (0);
-}
-
 int
 isc___rwlock_unlock(isc__rwlock_t *rwl, isc_rwlocktype_t type) {
        int32_t prev_cnt;