platform: remove reader/writer locks

The only thing using this was the transport lookups, but as
those transports are now fully initialized in nng_init, we
no longer need to lock that at all.

src/core/platform.h

@@ -85,11 +85,9 @@ extern void *nni_zalloc(size_t);
 // Most implementations can just call free() here.
 extern void nni_free(void *, size_t);
 
-typedef struct nni_plat_mtx    nni_plat_mtx;
-typedef struct nni_plat_rwlock nni_plat_rwlock;
-typedef struct nni_plat_cv     nni_plat_cv;
-typedef struct nni_plat_thr    nni_plat_thr;
-typedef struct nni_rwlock      nni_rwlock;
+typedef struct nni_plat_mtx nni_plat_mtx;
+typedef struct nni_plat_cv  nni_plat_cv;
+typedef struct nni_plat_thr nni_plat_thr;
 
 //
 // Threading & Synchronization Support
@@ -111,15 +109,6 @@ extern void nni_plat_mtx_lock(nni_plat_mtx *);
 // thread that owned the mutex.
 extern void nni_plat_mtx_unlock(nni_plat_mtx *);
 
-// read/write locks - these work like mutexes except that multiple readers
-// can acquire the lock.  These are not safe for recursive use, and it is
-// unspecified whether any measures are provided to prevent starvation.
-extern void nni_rwlock_init(nni_rwlock *);
-extern void nni_rwlock_fini(nni_rwlock *);
-extern void nni_rwlock_rdlock(nni_rwlock *);
-extern void nni_rwlock_wrlock(nni_rwlock *);
-extern void nni_rwlock_unlock(nni_rwlock *);
-
 // nni_plat_cv_init initializes a condition variable.  We require a mutex be
 // supplied with it, and that mutex must always be held when performing any
 // operations on the condition variable (other than fini.)  As with mutexes, an

src/platform/posix/posix_impl.h

@@ -65,15 +65,6 @@ struct nni_plat_mtx {
 		PTHREAD_MUTEX_INITIALIZER \
 	}
 
-struct nni_rwlock {
-	pthread_rwlock_t rwl;
-};
-
-#define NNI_RWLOCK_INITIALIZER             \
-	{                                  \
-		PTHREAD_RWLOCK_INITIALIZER \
-	}
-
 // No static form of CV initialization because of the need to use
 // attributes to set the clock type.
 struct nni_plat_cv {

src/platform/posix/posix_thread.c

@@ -155,53 +155,6 @@ nni_plat_mtx_unlock(nni_plat_mtx *mtx)
 	nni_pthread_mutex_unlock(&mtx->mtx);
 }
 
-void
-nni_rwlock_init(nni_rwlock *rwl)
-{
-	while (pthread_rwlock_init(&rwl->rwl, NULL) != 0) {
-		// We must have memory exhaustion -- ENOMEM, or
-		// in some cases EAGAIN.  Wait a bit before we try to
-		// give things a chance to settle down.
-		nni_msleep(10);
-	}
-}
-
-void
-nni_rwlock_fini(nni_rwlock *rwl)
-{
-	int rv;
-	if ((rv = pthread_rwlock_destroy(&rwl->rwl)) != 0) {
-		nni_panic("pthread_rwlock_destroy: %s", strerror(rv));
-	}
-}
-
-void
-nni_rwlock_rdlock(nni_rwlock *rwl)
-{
-	int rv;
-	if ((rv = pthread_rwlock_rdlock(&rwl->rwl)) != 0) {
-		nni_panic("pthread_rwlock_rdlock: %s", strerror(rv));
-	}
-}
-
-void
-nni_rwlock_wrlock(nni_rwlock *rwl)
-{
-	int rv;
-	if ((rv = pthread_rwlock_wrlock(&rwl->rwl)) != 0) {
-		nni_panic("pthread_rwlock_wrlock: %s", strerror(rv));
-	}
-}
-
-void
-nni_rwlock_unlock(nni_rwlock *rwl)
-{
-	int rv;
-	if ((rv = pthread_rwlock_unlock(&rwl->rwl)) != 0) {
-		nni_panic("pthread_rwlock_unlock: %s", strerror(rv));
-	}
-}
-
 void
 nni_plat_cv_init(nni_plat_cv *cv, nni_plat_mtx *mtx)
 {

src/platform/windows/win_impl.h

@@ -44,16 +44,6 @@ struct nni_plat_mtx {
 		SRWLOCK_INIT \
 	}
 
-struct nni_rwlock {
-	SRWLOCK rwl;
-	BOOLEAN exclusive;
-};
-
-#define NNI_RWLOCK_INITIALIZER \
-	{                      \
-		SRWLOCK_INIT   \
-	}
-
 struct nni_plat_cv {
 	CONDITION_VARIABLE cv;
 	PSRWLOCK           srl;

src/platform/windows/win_thread.c

@@ -1,5 +1,5 @@
 //
-// Copyright 2024 Staysail Systems, Inc. <[email protected]>
+// Copyright 2025 Staysail Systems, Inc. <[email protected]>
 // Copyright 2018 Capitar IT Group BV <[email protected]>
 //
 // This software is supplied under the terms of the MIT License, a
@@ -78,42 +78,6 @@ nni_plat_mtx_unlock(nni_plat_mtx *mtx)
 	ReleaseSRWLockExclusive(&mtx->srl);
 }
 
-void
-nni_rwlock_init(nni_rwlock *rwl)
-{
-	InitializeSRWLock(&rwl->rwl);
-}
-
-void
-nni_rwlock_fini(nni_rwlock *rwl)
-{
-	rwl->exclusive = FALSE;
-}
-
-void
-nni_rwlock_rdlock(nni_rwlock *rwl)
-{
-	AcquireSRWLockShared(&rwl->rwl);
-}
-
-void
-nni_rwlock_wrlock(nni_rwlock *rwl)
-{
-	AcquireSRWLockExclusive(&rwl->rwl);
-	rwl->exclusive = TRUE;
-}
-
-void
-nni_rwlock_unlock(nni_rwlock *rwl)
-{
-	if (rwl->exclusive) {
-		rwl->exclusive = FALSE;
-		ReleaseSRWLockExclusive(&rwl->rwl);
-	} else {
-		ReleaseSRWLockShared(&rwl->rwl);
-	}
-}
-
 void
 nni_plat_cv_init(nni_plat_cv *cv, nni_plat_mtx *mtx)
 {

src/sp/transport.c

@@ -1,5 +1,5 @@
 //
-// Copyright 2024 Staysail Systems, Inc. <[email protected]>
+// Copyright 2025 Staysail Systems, Inc. <[email protected]>
 // Copyright 2018 Capitar IT Group BV <[email protected]>
 // Copyright 2019 Devolutions <[email protected]>
 //
@@ -16,7 +16,6 @@
 
 static nni_list sp_tran_list =
     NNI_LIST_INITIALIZER(sp_tran_list, nni_sp_tran, tran_link);
-static nni_rwlock sp_tran_lk = NNI_RWLOCK_INITIALIZER;
 
 void
 nni_sp_tran_register(nni_sp_tran *tran)
@@ -55,14 +54,12 @@ nni_sp_tran_register(nni_sp_tran *tran)
 	}
 #endif
 
-	nni_rwlock_wrlock(&sp_tran_lk);
 	if (!nni_list_node_active(&tran->tran_link)) {
 		tran->tran_init();
 		nni_list_append(&sp_tran_list, tran);
 		nng_log_info(
 		    "NNG-TRAN", "Registered transport: %s", tran->tran_scheme);
 	}
-	nni_rwlock_unlock(&sp_tran_lk);
 }
 
 nni_sp_tran *
@@ -71,16 +68,13 @@ nni_sp_tran_find(const char *url)
 	// address is of the form "<scheme>://blah..."
 	nni_sp_tran *t;
 
-	nni_rwlock_rdlock(&sp_tran_lk);
 	NNI_LIST_FOREACH (&sp_tran_list, t) {
 		size_t len = strlen(t->tran_scheme);
 		if ((strncmp(url, t->tran_scheme, len) == 0) &&
 		    (url[len] == ':' || url[len] == '\0')) {
-			nni_rwlock_unlock(&sp_tran_lk);
 			return (t);
 		}
 	}
-	nni_rwlock_unlock(&sp_tran_lk);
 	return (NULL);
 }