Explicitly load atomic values in lib/isc/rwlock.c

diff --git a/lib/isc/rwlock.c b/lib/isc/rwlock.c
index 332848823d24bc90fd81722e34907baa4c33ebe6..b3151465a15ef9da520dece3c10d0fba46360e14 100644 (file)
--- a/lib/isc/rwlock.c
+++ b/lib/isc/rwlock.c
@@ -63,8 +63,10 @@ print_lock(const char *operation, isc_rwlock_t *rwl, isc_rwlocktype_t type) {
                                ISC_MSG_READ, "read") :
                 isc_msgcat_get(isc_msgcat, ISC_MSGSET_RWLOCK,
                                ISC_MSG_WRITE, "write")),
-               rwl->write_requests, rwl->write_completions,
-               rwl->cnt_and_flag, rwl->readers_waiting,
+               atomic_load_explicit(&rwl->write_requests, memory_order_relaxed),
+               atomic_load_explicit(&rwl->write_completions, memory_order_relaxed),
+               atomic_load_explicit(&rwl->cnt_and_flag, memory_order_relaxed),
+               rwl->readers_waiting,
                rwl->write_granted, rwl->write_quota);
 }
 #endif /* ISC_RWLOCK_TRACE */
@@ -84,9 +86,9 @@ isc_rwlock_init(isc_rwlock_t *rwl, unsigned int read_quota,
        rwl->magic = 0;
 
        rwl->spins = 0;
-       rwl->write_requests = 0;
-       rwl->write_completions = 0;
-       rwl->cnt_and_flag = 0;
+       atomic_init(&rwl->write_requests, 0);
+       atomic_init(&rwl->write_completions, 0);
+       atomic_init(&rwl->cnt_and_flag, 0);
        rwl->readers_waiting = 0;
        rwl->write_granted = 0;
        if (read_quota != 0) {
@@ -138,8 +140,9 @@ void
 isc_rwlock_destroy(isc_rwlock_t *rwl) {
        REQUIRE(VALID_RWLOCK(rwl));
 
-       REQUIRE(rwl->write_requests == rwl->write_completions &&
-               rwl->cnt_and_flag == 0 && rwl->readers_waiting == 0);
+       REQUIRE(atomic_load_explicit(&rwl->write_requests, memory_order_relaxed) ==
+               atomic_load_explicit(&rwl->write_completions, memory_order_relaxed) &&
+               atomic_load_explicit(&rwl->cnt_and_flag, memory_order_relaxed) == 0 && rwl->readers_waiting == 0);
 
        rwl->magic = 0;
        (void)isc_condition_destroy(&rwl->readable);
@@ -224,10 +227,13 @@ isc__rwlock_lock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
 #endif
 
        if (type == isc_rwlocktype_read) {
-               if (rwl->write_requests != rwl->write_completions) {
+               if (atomic_load_explicit(&rwl->write_requests, memory_order_relaxed) !=
+                   atomic_load_explicit(&rwl->write_completions, memory_order_relaxed))
+               {
                        /* there is a waiting or active writer */
                        LOCK(&rwl->lock);
-                       if (rwl->write_requests != rwl->write_completions) {
+                       if (atomic_load_explicit(&rwl->write_requests, memory_order_relaxed) !=
+                           atomic_load_explicit(&rwl->write_completions, memory_order_relaxed)) {
                                rwl->readers_waiting++;
                                WAIT(&rwl->readable, &rwl->lock);
                                rwl->readers_waiting--;
@@ -240,14 +246,15 @@ isc__rwlock_lock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
                                                    memory_order_relaxed);
                POST(cntflag);
                while (1) {
-                       if ((rwl->cnt_and_flag & WRITER_ACTIVE) == 0)
+                       if ((atomic_load_explicit(&rwl->cnt_and_flag, memory_order_relaxed) & WRITER_ACTIVE) == 0)
                                break;
 
                        /* A writer is still working */
                        LOCK(&rwl->lock);
                        rwl->readers_waiting++;
-                       if ((rwl->cnt_and_flag & WRITER_ACTIVE) != 0)
+                       if ((atomic_load_explicit(&rwl->cnt_and_flag, memory_order_relaxed) & WRITER_ACTIVE) != 0) {
                                WAIT(&rwl->readable, &rwl->lock);
+                       }
                        rwl->readers_waiting--;
                        UNLOCK(&rwl->lock);
 
@@ -289,9 +296,9 @@ isc__rwlock_lock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
                /* enter the waiting queue, and wait for our turn */
                prev_writer = atomic_fetch_add_explicit(&rwl->write_requests, 1,
                                                        memory_order_relaxed);
-               while (rwl->write_completions != prev_writer) {
+               while (atomic_load_explicit(&rwl->write_completions, memory_order_relaxed) != prev_writer) {
                        LOCK(&rwl->lock);
-                       if (rwl->write_completions != prev_writer) {
+                       if (atomic_load_explicit(&rwl->write_completions, memory_order_relaxed) != prev_writer) {
                                WAIT(&rwl->writeable, &rwl->lock);
                                UNLOCK(&rwl->lock);
                                continue;
@@ -311,12 +318,13 @@ isc__rwlock_lock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
 
                        /* Another active reader or writer is working. */
                        LOCK(&rwl->lock);
-                       if (rwl->cnt_and_flag != 0)
+                       if (atomic_load_explicit(&rwl->cnt_and_flag, memory_order_relaxed) != 0) {
                                WAIT(&rwl->writeable, &rwl->lock);
+                       }
                        UNLOCK(&rwl->lock);
                }
 
-               INSIST((rwl->cnt_and_flag & WRITER_ACTIVE) != 0);
+               INSIST((atomic_load_explicit(&rwl->cnt_and_flag, memory_order_relaxed) & WRITER_ACTIVE));
                rwl->write_granted++;
        }
 
@@ -365,7 +373,8 @@ isc_rwlock_trylock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
 
        if (type == isc_rwlocktype_read) {
                /* If a writer is waiting or working, we fail. */
-               if (rwl->write_requests != rwl->write_completions)
+               if (atomic_load_explicit(&rwl->write_requests, memory_order_relaxed) !=
+                   atomic_load_explicit(&rwl->write_completions, memory_order_relaxed))
                        return (ISC_R_LOCKBUSY);
 
                /* Otherwise, be ready for reading. */
@@ -385,7 +394,8 @@ isc_rwlock_trylock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
                         * new writers in this short period, wake them up.
                         */
                        if (cntflag == READER_INCR &&
-                           rwl->write_completions != rwl->write_requests) {
+                           atomic_load_explicit(&rwl->write_completions, memory_order_relaxed) !=
+                           atomic_load_explicit(&rwl->write_requests, memory_order_relaxed)) {
                                LOCK(&rwl->lock);
                                BROADCAST(&rwl->writeable);
                                UNLOCK(&rwl->lock);
@@ -501,7 +511,8 @@ isc_rwlock_unlock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
                 * FIFO order.
                 */
                if (prev_cnt == READER_INCR &&
-                   rwl->write_completions != rwl->write_requests) {
+                   atomic_load_explicit(&rwl->write_completions, memory_order_relaxed) !=
+                   atomic_load_explicit(&rwl->write_requests, memory_order_relaxed)) {
                        LOCK(&rwl->lock);
                        BROADCAST(&rwl->writeable);
                        UNLOCK(&rwl->lock);
@@ -519,8 +530,9 @@ isc_rwlock_unlock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
                                          memory_order_relaxed);
 
                if (rwl->write_granted >= rwl->write_quota ||
-                   rwl->write_requests == rwl->write_completions ||
-                   (rwl->cnt_and_flag & ~WRITER_ACTIVE) != 0) {
+                   (atomic_load_explicit(&rwl->write_requests, memory_order_relaxed) ==
+                   atomic_load_explicit(&rwl->write_completions, memory_order_relaxed)) ||
+                   (atomic_load_explicit(&rwl->cnt_and_flag, memory_order_relaxed) & ~WRITER_ACTIVE)) {
                        /*
                         * We have passed the write quota, no writer is
                         * waiting, or some readers are almost ready, pending
@@ -537,7 +549,8 @@ isc_rwlock_unlock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
                        UNLOCK(&rwl->lock);
                }
 
-               if (rwl->write_requests != rwl->write_completions &&
+               if ((atomic_load_explicit(&rwl->write_requests, memory_order_relaxed) !=
+                    atomic_load_explicit(&rwl->write_completions, memory_order_relaxed)) &&
                    wakeup_writers) {
                        LOCK(&rwl->lock);
                        BROADCAST(&rwl->writeable);