fixes #1409 reader/writer lock desired

This provides the initial implementation, and converts the
transport lookup routines to use it.  This is probably of limited
performance benefit, but rwlock's may be useful in further future work.

2 files changed, 55 insertions, 7 deletions

diff --git a/src/platform/posix/posix_impl.h b/src/platform/posix/posix_impl.h
index 978afc01..851c80dc 100644
--- a/src/platform/posix/posix_impl.h
+++ b/src/platform/posix/posix_impl.h
@@ -1,5 +1,5 @@
 //
-// Copyright 2020 Staysail Systems, Inc. <info@staysail.tech>
+// Copyright 2021 Staysail Systems, Inc. <info@staysail.tech>
 // Copyright 2018 Capitar IT Group BV <info@capitar.com>
 //
 // This software is supplied under the terms of the MIT License, a
@@ -58,6 +58,10 @@ struct nni_plat_mtx {
 	pthread_mutex_t mtx;
 };
 
+struct nni_rwlock {
+	pthread_rwlock_t rwl;
+};
+
 struct nni_plat_cv {
 	pthread_cond_t cv;
 	nni_plat_mtx * mtx;
diff --git a/src/platform/posix/posix_thread.c b/src/platform/posix/posix_thread.c
index ed4ec031..c47bcec6 100644
--- a/src/platform/posix/posix_thread.c
+++ b/src/platform/posix/posix_thread.c
@@ -1,5 +1,5 @@
 //
-// Copyright 2020 Staysail Systems, Inc. <info@staysail.tech>
+// Copyright 2021 Staysail Systems, Inc. <info@staysail.tech>
 // Copyright 2018 Capitar IT Group BV <info@capitar.com>
 //
 // This software is supplied under the terms of the MIT License, a
@@ -81,7 +81,6 @@ static void
 nni_pthread_mutex_lock(pthread_mutex_t *m)
 {
 	int rv;
-
 	if ((rv = pthread_mutex_lock(m)) != 0) {
 		nni_panic("pthread_mutex_lock: %s", strerror(rv));
 	}
@@ -91,7 +90,6 @@ static void
 nni_pthread_mutex_unlock(pthread_mutex_t *m)
 {
 	int rv;
-
 	if ((rv = pthread_mutex_unlock(m)) != 0) {
 		nni_panic("pthread_mutex_unlock: %s", strerror(rv));
 	}
@@ -101,7 +99,6 @@ static void
 nni_pthread_cond_broadcast(pthread_cond_t *c)
 {
 	int rv;
-
 	if ((rv = pthread_cond_broadcast(c)) != 0) {
 		nni_panic("pthread_cond_broadcast: %s", strerror(rv));
 	}
@@ -156,6 +153,53 @@ nni_plat_mtx_unlock(nni_plat_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)
 {
 	// See the comments in nni_plat_mtx_init.  Almost everywhere this
@@ -264,7 +308,7 @@ nni_plat_thr_set_name(nni_plat_thr *thr, const char *name)
 #if defined(__APPLE__)
 	// Darwin is weird, it can only set the name of pthread_self.
 	if ((thr == NULL) || (pthread_self() == thr->tid)) {
-        	pthread_setname_np(name);
+		pthread_setname_np(name);
 	}
 #elif defined(__NetBSD__)
 	if (thr == NULL) {
@@ -283,7 +327,7 @@ nni_plat_thr_set_name(nni_plat_thr *thr, const char *name)
 	if (thr == NULL) {
 		pthread_set_name_np(pthread_self(), name);
 	} else {
-        	pthread_set_name_np(thr->tid, name);
+		pthread_set_name_np(thr->tid, name);
 	}
 #endif
 }