9os

commit ad5b0eca116e3da5049a37627402b2ee363e5985
parent d03a32a2cbe192dbf7bbf098ce2227d97d156390
Author: Roberto E. Vargas Caballero <roberto.vargas@midokura.com>
Date:   Tue, 22 Nov 2022 19:25:24 +0100

os9: Refcount channels when cloning fds

Channels can be shared between different fds and we cannot free
a channel without ref counting it usage.

Diffstat:
M
include/os9/os9.h
 | 
1
+
M
src/os9/dev/dev.c
 | 
31
+++++++++++++++++++++++++++++--

2 files changed, 30 insertions(+), 2 deletions(-)
diff --git a/include/os9/os9.h b/include/os9/os9.h
@@ -153,6 +153,7 @@ struct dir {
 };
 
 struct chan {
+	Ref ref;
 	long offset;
 	int index;
 	Qid qid;
diff --git a/src/os9/dev/dev.c b/src/os9/dev/dev.c
@@ -43,6 +43,7 @@ newchan(unsigned char type)
 	if ((c = allocchan()) == NULL)
 		goto err2;
 	memset(c, 0, sizeof(*c));
+	initref(&c->ref);
 	c->type = type;
 
 	lock(&c->mutex);
@@ -75,14 +76,26 @@ newspace(Nspace *from)
 Fdset *
 newfds(Fdset *from)
 {
+	int i;
+	Chan *c;
 	Fdset *fds;
 
 	if ((fds = allocfds()) == NULL)
 		return NULL;
-
-	*fds = (from) ? *from : (Fdset) {0};
+	memset(fds, 0, sizeof(*fds));
 	initref(&fds->ref);
 
+	if (!from)
+		return fds;
+
+	lock(&from->m);
+	for (i = 0; i < NR_CHANS; ++i) {
+		c = fds->fdset[i] = from->fdset[i];
+		if (c)
+			incref(&c->ref);
+	}
+	unlock(&from->m);
+
 	return fds;
 }
 
@@ -97,8 +110,19 @@ delspace(Nspace *ns)
 void
 delfds(Fdset *fds)
 {
+	int i;
+	Chan *c;
+
 	if (!decref(&fds->ref))
 		return;
+
+	for (i = 0; i < NR_CHANS; ++i) {
+		c = fds->fdset[i];
+		if (!c)
+			continue;
+		lock(&c->mutex);
+		devclose(c);
+	}
 	freefds(fds);
 }
 
@@ -108,6 +132,9 @@ delchan(Chan *c)
 	Chan **bp;
 	Fdset *fds = proc->fds;
 
+	if (!decref(&c->ref))
+		return;
+
 	lock(&fds->m);
 	for (bp = fds->fdset; bp < &fds->fdset[NR_CHANS]; ++bp) {
 		if (*bp == c)