fixes #1112 POSIX pollq finalizers could be simpler

We reap the connections when closing, to ensure that the clean up is
done outside the pollq thread.  This also reduces pressure on the
pollq, we think.  But more importantly it eliminates some complex
code that was meant to avoid deadlocks, but ultimately created other
use-after-free challenges.  This work is an enabler for further
simplifications in the aio/task logic.  While here we converted some
potentially racy locking of the dialers and reference counts to simpler
lock-free reference counting.

1 files changed, 23 insertions, 9 deletions

diff --git a/src/platform/posix/posix_ipcconn.c b/src/platform/posix/posix_ipcconn.c
index 2b078aa5..e4d783f3 100644
--- a/src/platform/posix/posix_ipcconn.c
+++ b/src/platform/posix/posix_ipcconn.c
@@ -1,5 +1,5 @@
 //
-// Copyright 2019 Staysail Systems, Inc. <info@staysail.tech>
+// Copyright 2020 Staysail Systems, Inc. <info@staysail.tech>
 // Copyright 2018 Capitar IT Group BV <info@capitar.com>
 // Copyright 2019 Devolutions <info@devolutions.net>
 //
@@ -200,7 +200,9 @@ ipc_close(void *arg)
 			nni_aio_list_remove(aio);
 			nni_aio_finish_error(aio, NNG_ECLOSED);
 		}
-		nni_posix_pfd_close(c->pfd);
+		if (c->pfd != NULL) {
+			nni_posix_pfd_close(c->pfd);
+		}
 	}
 	nni_mtx_unlock(&c->mtx);
 }
@@ -483,14 +485,13 @@ nni_posix_ipc_start(nni_ipc_conn *c)
 }
 
 static void
-ipc_free(void *arg)
+ipc_reap(void *arg)
 {
 	ipc_conn *c = arg;
 	ipc_close(c);
-	nni_posix_pfd_fini(c->pfd);
-	nni_mtx_lock(&c->mtx); // not strictly needed, but shut up TSAN
-	c->pfd = NULL;
-	nni_mtx_unlock(&c->mtx);
+	if (c->pfd != NULL) {
+		nni_posix_pfd_fini(c->pfd);
+	}
 	nni_mtx_fini(&c->mtx);
 
 	if (c->dialer != NULL) {
@@ -500,6 +501,13 @@ ipc_free(void *arg)
 	NNI_FREE_STRUCT(c);
 }
 
+static void
+ipc_free(void *arg)
+{
+	ipc_conn *c = arg;
+	nni_reap(&c->reap, ipc_reap, c);
+}
+
 static const nni_option ipc_options[] = {
 	{
 	    .o_name = NNG_OPT_LOCADDR,
@@ -545,7 +553,7 @@ ipc_setx(void *arg, const char *name, const void *val, size_t sz, nni_type t)
 }
 
 int
-nni_posix_ipc_init(nni_ipc_conn **cp, nni_posix_pfd *pfd)
+nni_posix_ipc_alloc(nni_ipc_conn **cp, nni_ipc_dialer *d)
 {
 	ipc_conn *c;
 
@@ -554,7 +562,7 @@ nni_posix_ipc_init(nni_ipc_conn **cp, nni_posix_pfd *pfd)
 	}
 
 	c->closed         = false;
-	c->pfd            = pfd;
+	c->dialer         = d;
 	c->stream.s_free  = ipc_free;
 	c->stream.s_close = ipc_close;
 	c->stream.s_send  = ipc_send;
@@ -569,3 +577,9 @@ nni_posix_ipc_init(nni_ipc_conn **cp, nni_posix_pfd *pfd)
 	*cp = c;
 	return (0);
 }
+
+void
+nni_posix_ipc_init(nni_ipc_conn *c, nni_posix_pfd *pfd)
+{
+	c->pfd = pfd;
+}