fixes #1408 Reference count as a first class type

src/core/CMakeLists.txt

@@ -57,6 +57,8 @@ nng_sources(
         protocol.h
         reap.c
         reap.h
+        refcnt.c
+        refcnt.h
         sockaddr.c
         socket.c
         socket.h

src/core/nng_impl.h

@@ -40,6 +40,7 @@
 #include "core/pollable.h"
 #include "core/protocol.h"
 #include "core/reap.h"
+#include "core/refcnt.h"
 #include "core/stats.h"
 #include "core/stream.h"
 #include "core/strs.h"

src/core/pipe.c

@@ -25,19 +25,31 @@ static nni_id_map pipes =
 static nni_mtx pipes_lk = NNI_MTX_INITIALIZER;
 
 static void pipe_destroy(void *);
+static void pipe_reap(void *);
 
 static nni_reap_list pipe_reap_list = {
 	.rl_offset = offsetof(nni_pipe, p_reap),
-	.rl_func   = pipe_destroy,
+	.rl_func   = pipe_reap,
 };
 
 static void
 pipe_destroy(void *arg)
 {
 	nni_pipe *p = arg;
-	if (p == NULL) {
-		return;
+
+	if (p->p_proto_data != NULL) {
+		p->p_proto_ops.pipe_fini(p->p_proto_data);
 	}
+	if (p->p_tran_data != NULL) {
+		p->p_tran_ops.p_fini(p->p_tran_data);
+	}
+	nni_free(p, p->p_size);
+}
+
+void
+pipe_reap(void *arg)
+{
+	nni_pipe *p = arg;
 
 	nni_pipe_run_cb(p, NNG_PIPE_EV_REM_POST);
 
@@ -47,32 +59,21 @@ pipe_destroy(void *arg)
 	if (p->p_id != 0) {
 		nni_id_remove(&pipes, p->p_id);
 	}
-	// This wait guarantees that all callers are done with us.
-	while (p->p_ref != 0) {
-		nni_cv_wait(&p->p_cv);
-	}
 	nni_mtx_unlock(&pipes_lk);
 
-	if (p->p_proto_data != NULL) {
-		p->p_proto_ops.pipe_stop(p->p_proto_data);
-	}
-	if ((p->p_tran_data != NULL) && (p->p_tran_ops.p_stop != NULL)) {
-		p->p_tran_ops.p_stop(p->p_tran_data);
-	}
-
 #ifdef NNG_ENABLE_STATS
 	nni_stat_unregister(&p->st_root);
 #endif
 	nni_pipe_remove(p);
 
 	if (p->p_proto_data != NULL) {
-		p->p_proto_ops.pipe_fini(p->p_proto_data);
+		p->p_proto_ops.pipe_stop(p->p_proto_data);
 	}
-	if (p->p_tran_data != NULL) {
-		p->p_tran_ops.p_fini(p->p_tran_data);
+	if ((p->p_tran_data != NULL) && (p->p_tran_ops.p_stop != NULL)) {
+		p->p_tran_ops.p_stop(p->p_tran_data);
 	}
-	nni_cv_fini(&p->p_cv);
-	nni_free(p, p->p_size);
+
+	nni_pipe_rele(p);
 }
 
 int
@@ -86,7 +87,7 @@ nni_pipe_find(nni_pipe **pp, uint32_t id)
 	// close the pipe.
 	nni_mtx_lock(&pipes_lk);
 	if ((p = nni_id_get(&pipes, id)) != NULL) {
-		p->p_ref++;
+		nni_refcnt_hold(&p->p_refcnt);
 		*pp = p;
 	}
 	nni_mtx_unlock(&pipes_lk);
@@ -96,12 +97,7 @@ nni_pipe_find(nni_pipe **pp, uint32_t id)
 void
 nni_pipe_rele(nni_pipe *p)
 {
-	nni_mtx_lock(&pipes_lk);
-	p->p_ref--;
-	if (p->p_ref == 0) {
-		nni_cv_wake(&p->p_cv);
-	}
-	nni_mtx_unlock(&pipes_lk);
+	nni_refcnt_rele(&p->p_refcnt);
 }
 
 // nni_pipe_id returns the 32-bit pipe id, which can be used in backtraces.
@@ -250,15 +246,14 @@ pipe_create(nni_pipe **pp, nni_sock *sock, nni_sp_tran *tran, void *tran_data)
 	p->p_proto_ops  = *pops;
 	p->p_sock       = sock;
 	p->p_cbs        = false;
-	p->p_ref        = 1;
+
+	nni_refcnt_init(&p->p_refcnt, 2, p, pipe_destroy);
 
 	nni_atomic_init_bool(&p->p_closed);
 	nni_atomic_flag_reset(&p->p_stop);
 	NNI_LIST_NODE_INIT(&p->p_sock_node);
 	NNI_LIST_NODE_INIT(&p->p_ep_node);
 
-	nni_cv_init(&p->p_cv, &pipes_lk);
-
 	nni_mtx_lock(&pipes_lk);
 	rv = nni_id_alloc32(&pipes, &p->p_id, p);
 	nni_mtx_unlock(&pipes_lk);

src/core/refcnt.c

@@ -0,0 +1,33 @@
+// Copyright 2024 Staysail Systems, Inc. <[email protected]>
+//
+// This software is supplied under the terms of the MIT License, a
+// copy of which should be located in the distribution where this
+// file was obtained (LICENSE.txt).  A copy of the license may also be
+// found online at https://opensource.org/licenses/MIT.
+//
+
+#include <core/refcnt.h>
+
+void
+nni_refcnt_init(
+    nni_refcnt *rc, unsigned value, void *data, void (*fini)(void *))
+{
+	nni_atomic_init(&rc->rc_cnt);
+	nni_atomic_set(&rc->rc_cnt, value);
+	rc->rc_data = data;
+	rc->rc_fini = fini;
+}
+
+void
+nni_refcnt_hold(nni_refcnt *rc)
+{
+	nni_atomic_inc(&rc->rc_cnt);
+}
+
+void
+nni_refcnt_rele(nni_refcnt *rc)
+{
+	if (nni_atomic_dec_nv(&rc->rc_cnt) == 0) {
+		rc->rc_fini(rc->rc_data);
+	}
+}

src/core/refcnt.h

@@ -0,0 +1,28 @@
+// Copyright 2024 Staysail Systems, Inc. <[email protected]>
+//
+// This software is supplied under the terms of the MIT License, a
+// copy of which should be located in the distribution where this
+// file was obtained (LICENSE.txt).  A copy of the license may also be
+// found online at https://opensource.org/licenses/MIT.
+//
+
+#ifndef CORE_REFCNT_H
+#define CORE_REFCNT_H
+
+#include <nng/nng.h>
+
+#include <core/nng_impl.h>
+#include <core/platform.h>
+
+typedef struct {
+	nni_atomic_int rc_cnt;
+	void (*rc_fini)(void *);
+	void *rc_data;
+} nni_refcnt;
+
+extern void nni_refcnt_init(
+    nni_refcnt *rc, unsigned value, void *v, void (*fini)(void *));
+extern void nni_refcnt_hold(nni_refcnt *rc);
+extern void nni_refcnt_rele(nni_refcnt *rc);
+
+#endif // CORE_REFCNT_H

src/core/sockimpl.h

@@ -105,9 +105,8 @@ struct nni_pipe {
 	nni_atomic_bool    p_closed;
 	nni_atomic_flag    p_stop;
 	bool               p_cbs;
-	int                p_ref;
-	nni_cv             p_cv;
 	nni_reap_node      p_reap;
+	nni_refcnt         p_refcnt;
 
 #ifdef NNG_ENABLE_STATS
 	nni_stat_item st_root;