From 755dcb223e9ca2aecd2555a417247d8f55fdaf33 Mon Sep 17 00:00:00 2001
From: Garrett D'Amore <garrett@damore.org>
Date: Thu, 28 Nov 2024 20:54:20 -0500
Subject: fixes #1408 Reference count as a first class type

This starts by using this for the nni_pipe, but we will use it
for the other primary objects as well.  This should simplify
the tear down and hopefully eliminate some races.

It does mean that pipe destruction goes through an additional
context switch, for now at least.  This shouldn't be on the hot
data path anyway.
---
 src/core/pipe.c | 53 ++++++++++++++++++++++++-----------------------------
 1 file changed, 24 insertions(+), 29 deletions(-)

(limited to 'src/core/pipe.c')

diff --git a/src/core/pipe.c b/src/core/pipe.c
index 1e2842dc..c54cdfe0 100644
--- a/src/core/pipe.c
+++ b/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);
-- 
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