9os

commit 79331ba68b0e49e606df1109b4b077cee0157ba4
parent 32c1c85ecd4b289f5f464b22deb113c89e81836f
Author: Roberto E. Vargas Caballero <roberto.vargas@midokura.com>
Date:   Tue, 22 Nov 2022 17:31:33 +0100

os9: Don't duplicate channels in RFFDG

RFFDG must duplicate the pointer table and not the channel
table itself.

Diffstat:
M
include/os9/os9.h
 | 
5
++++-
M
src/os9/alloc.c
 | 
36
++++++++++++++++++++++++++++++++++++
M
src/os9/dev/dev.c
 | 
102
+++++++++++++++++++++++++++++++++++++++++++++----------------------------------

3 files changed, 98 insertions(+), 45 deletions(-)
diff --git a/include/os9/os9.h b/include/os9/os9.h
@@ -160,6 +160,7 @@ struct chan {
 	unsigned char dev;
 	unsigned char mode;
 	mutex_t mutex;
+	Chan *next;
 };
 
 struct mpoint {
@@ -179,7 +180,7 @@ struct nspace {
 struct fdset {
 	Ref ref;
 	mutex_t m;
-	Chan fdset[NR_CHANS];
+	Chan *fdset[NR_CHANS];
 	Fdset *next;
 };
 
@@ -270,11 +271,13 @@ extern Page *allocp(phyaddr_t);
 extern Nspace *allocspace(void);
 extern Map *allocmap(void);
 extern Fdset *allocfds(void);
+extern Chan *allocchan(void);
 extern void freeb(void *);
 extern void freep(Page *);
 extern void freespace(Nspace *);
 extern void freemap(Map *);
 extern void freefds(Fdset *);
+extern void freechan(Chan *);
 extern void ialloc(void);
 
 /* map.c */
diff --git a/src/os9/alloc.c b/src/os9/alloc.c
@@ -36,12 +36,18 @@ struct mappool {
         mutex_t m;
 };
 
+struct chanpool {
+	Chan *list;
+	mutex_t m;
+};
+
 static union bucket *heap;
 static struct bufpool bufpool;
 static struct pagepool pagepool;
 static struct nspool nspool;
 static struct mappool mappool;
 static struct fdspool fdspool;
+static struct chanpool chanpool;
 
 void
 freeb(void *bp)
@@ -255,6 +261,36 @@ freep(Page *p)
 	unlock(&pagepool.m);
 }
 
+Chan *
+allocchan(void)
+{
+	Chan *c;
+
+	lock(&chanpool.m);
+	if (chanpool.list) {
+		c = chanpool.list;
+		chanpool.list = c->next;
+	} else {
+		if ((c = alloc(sizeof(*c))) == NULL)
+			return NULL;
+	}
+	unlock(&chanpool.m);
+
+	return c;
+}
+
+void
+freechan(Chan *c)
+{
+	if (!c)
+		return;
+
+	lock(&chanpool.m);
+	c->next = chanpool.list;
+	chanpool.list = c;
+	unlock(&chanpool.m);
+}
+
 void
 ialloc(void)
 {
diff --git a/src/os9/dev/dev.c b/src/os9/dev/dev.c
@@ -9,7 +9,7 @@
 #include "dev.h"
 
 /*
- * Lock policy: TODO: Change the lock policy because it generates problems
+ * Lock policy:
  * The channels are locked when accessed from the raw fdset array, which is
  * currently done by newchan() and fd2chan().
  * The channels are propagated through the functions in a locked state.
@@ -29,24 +29,33 @@ sameqid(Qid q1, Qid q2)
 Chan *
 newchan(unsigned char type)
 {
-	int i;
-	Chan *c = NULL;
-	Chan *fdset = proc->fds->fdset;
+	Chan *c, **bp;
+	Fdset *fds = proc->fds;
 
-	for (i = 0; i < NR_CHANS; i++) {
-		c = &fdset[i];
-		if (!trylock(&c->mutex))
-			continue;
-		if (c->type == NODEV) {
-			c->type = type;
+	lock(&fds->m);
+	for (bp = fds->fdset; bp < &fds->fdset[NR_CHANS]; ++bp) {
+		if (*bp == NULL)
 			break;
-		}
-		unlock(&c->mutex);
 	}
 
-	if (!c)
-		errno = ENOMEM;
+	if (bp == &fds->fdset[NR_CHANS])
+		goto err1;
+	if ((c = allocchan()) == NULL)
+		goto err2;
+	memset(c, 0, sizeof(*c));
+	c->type = type;
+
+	lock(&c->mutex);
+	*bp = c;
+	unlock(&fds->m);
+
 	return c;
+
+err1:
+	errno = ENOMEM;
+err2:
+	unlock(&fds->m);
+	return NULL;
 }
 
 Nspace *
@@ -96,45 +105,45 @@ delfds(Fdset *fds)
 void
 delchan(Chan *c)
 {
-	c->qid = QID(0, 0, 0);
-	c->dev = 0;
-	c->offset = 0;
-	c->index = 0;
-	c->type = NODEV;
+	Chan **bp;
+	Fdset *fds = proc->fds;
+
+	lock(&fds->m);
+	for (bp = fds->fdset; bp < &fds->fdset[NR_CHANS]; ++bp) {
+		if (*bp == c)
+			break;
+	}
+	if (bp == &fds->fdset[NR_CHANS])
+		panic("corrupted channel");
+
+	*bp = NULL;
+	unlock(&fds->m);
 	unlock(&c->mutex);
+
+	freechan(c);
 }
 
 static Chan *
 fd2chan(int fd)
 {
 	Chan *c;
-	Chan *fdset = proc->fds->fdset;
 
 	if (fd < 0 || fd >= NR_CHANS)
-		goto badfd;
+		goto err;
 
-	c = &fdset[fd];
+	c = proc->fds->fdset[fd];
+	if (!c)
+		goto err;
 	lock(&c->mutex);
-	if (c->type == NODEV)
-		goto ubadfd;
+
 	return c;
 
-ubadfd:
-	unlock(&c->mutex);
-badfd:
+err:
 	errno = EBADF;
 	return NULL;
 }
 
 static int
-chan2fd(Chan *c)
-{
-	Chan *fdset = proc->fds->fdset;
-
-	return (c == NULL) ? -1 : (c - fdset);
-}
-
-static int
 validmode(int mode)
 {
 	if ((mode & O_READ) &&  (mode & (O_WRITE | O_RDWR)))
@@ -429,15 +438,24 @@ devopen(char *fname, int mode)
 int
 open(char *fname, int mode)
 {
-	int r;
-	Chan *c;
+	int fd;
+	Chan *c, **bp;
+	Fdset *fds = proc->fds;
 
 	if ((c = devopen(fname, mode)) == NULL)
 		return -1;
-	r = chan2fd(c);
-	unlock(&c->mutex);
 
-	return r;
+	lock(&fds->m);
+	for (bp = fds->fdset; bp < &fds->fdset[NR_CHANS]; ++bp) {
+		if (*bp == c)
+			break;
+	}
+	fd = (bp == &fds->fdset[NR_CHANS]) ? -1 : (bp - fds->fdset);
+	unlock(&fds->m);
+
+	if (fd == -1)
+		panic("corrupted channel");
+	return fd;
 }
 
 int
@@ -773,10 +791,6 @@ void
 idev(void)
 {
 	Chan *c;
-	Chan *fdset = proc->fds->fdset;
-
-	for (c = fdset; c < &fdset[NR_CHANS]; c++)
-		c->type = NODEV;
 
 	if ((c = attach('/', 0)) == NULL)
 		panic("idev:attach");