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From: Juergen Gross <jgross@suse.com>
To: xen-devel@lists.xenproject.org
Cc: Juergen Gross <jgross@suse.com>, Ian Jackson <iwj@xenproject.org>,
	Wei Liu <wl@xen.org>
Subject: [PATCH RFC 1/4] tools/xenstore: simplify xenstored main loop
Date: Fri, 22 Jan 2021 10:23:21 +0100	[thread overview]
Message-ID: <20210122092324.7178-2-jgross@suse.com> (raw)
In-Reply-To: <20210122092324.7178-1-jgross@suse.com>

The main loop of xenstored is rather complicated due to different
handling of socket and ring-page interfaces. Unify that handling by
introducing interface type specific functions can_read() and
can_write().

Put the interface type specific functions in an own structure and let
struct connection contain only a pointer to that new function vector.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 tools/xenstore/xenstored_core.c   | 118 +++++++++++++++++-------------
 tools/xenstore/xenstored_core.h   |  16 ++--
 tools/xenstore/xenstored_domain.c |  11 ++-
 3 files changed, 85 insertions(+), 60 deletions(-)

diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
index 65ecdd0568..c89f5202fe 100644
--- a/tools/xenstore/xenstored_core.c
+++ b/tools/xenstore/xenstored_core.c
@@ -226,8 +226,8 @@ static bool write_messages(struct connection *conn)
 				sockmsg_string(out->hdr.msg.type),
 				out->hdr.msg.len,
 				out->buffer, conn);
-		ret = conn->write(conn, out->hdr.raw + out->used,
-				  sizeof(out->hdr) - out->used);
+		ret = conn->funcs->write(conn, out->hdr.raw + out->used,
+					 sizeof(out->hdr) - out->used);
 		if (ret < 0)
 			return false;
 
@@ -243,8 +243,8 @@ static bool write_messages(struct connection *conn)
 			return true;
 	}
 
-	ret = conn->write(conn, out->buffer + out->used,
-			  out->hdr.msg.len - out->used);
+	ret = conn->funcs->write(conn, out->buffer + out->used,
+				 out->hdr.msg.len - out->used);
 	if (ret < 0)
 		return false;
 
@@ -1520,8 +1520,8 @@ static void handle_input(struct connection *conn)
 	/* Not finished header yet? */
 	if (in->inhdr) {
 		if (in->used != sizeof(in->hdr)) {
-			bytes = conn->read(conn, in->hdr.raw + in->used,
-					   sizeof(in->hdr) - in->used);
+			bytes = conn->funcs->read(conn, in->hdr.raw + in->used,
+						  sizeof(in->hdr) - in->used);
 			if (bytes < 0)
 				goto bad_client;
 			in->used += bytes;
@@ -1546,8 +1546,8 @@ static void handle_input(struct connection *conn)
 		in->inhdr = false;
 	}
 
-	bytes = conn->read(conn, in->buffer + in->used,
-			   in->hdr.msg.len - in->used);
+	bytes = conn->funcs->read(conn, in->buffer + in->used,
+				  in->hdr.msg.len - in->used);
 	if (bytes < 0)
 		goto bad_client;
 
@@ -1570,7 +1570,7 @@ static void handle_output(struct connection *conn)
 		ignore_connection(conn);
 }
 
-struct connection *new_connection(connwritefn_t *write, connreadfn_t *read)
+struct connection *new_connection(struct interface_funcs *funcs)
 {
 	struct connection *new;
 
@@ -1580,8 +1580,7 @@ struct connection *new_connection(connwritefn_t *write, connreadfn_t *read)
 
 	new->fd = -1;
 	new->pollfd_idx = -1;
-	new->write = write;
-	new->read = read;
+	new->funcs = funcs;
 	new->is_ignored = false;
 	new->transaction_started = 0;
 	INIT_LIST_HEAD(&new->out_list);
@@ -1622,6 +1621,16 @@ int readfd(struct connection *conn, void *data, unsigned int len)
 	errno = EBADF;
 	return -1;
 }
+
+static bool socket_can_write(struct connection *conn)
+{
+	return false;
+}
+
+static bool socket_can_read(struct connection *conn)
+{
+	return false;
+}
 #else
 int writefd(struct connection *conn, const void *data, unsigned int len)
 {
@@ -1661,6 +1670,32 @@ int readfd(struct connection *conn, void *data, unsigned int len)
 	return rc;
 }
 
+static bool socket_can_write(struct connection *conn)
+{
+	if (conn->pollfd_idx == -1)
+		return false;
+
+	if (fds[conn->pollfd_idx].revents & ~(POLLIN | POLLOUT)) {
+		talloc_free(conn);
+		return false;
+	}
+
+	return fds[conn->pollfd_idx].revents & POLLOUT;
+}
+
+static bool socket_can_read(struct connection *conn)
+{
+	if (conn->pollfd_idx == -1)
+		return false;
+
+	if (fds[conn->pollfd_idx].revents & ~(POLLIN | POLLOUT)) {
+		talloc_free(conn);
+		return false;
+	}
+
+	return fds[conn->pollfd_idx].revents & POLLIN;
+}
+
 static void accept_connection(int sock)
 {
 	int fd;
@@ -1670,7 +1705,7 @@ static void accept_connection(int sock)
 	if (fd < 0)
 		return;
 
-	conn = new_connection(writefd, readfd);
+	conn = new_connection(&socket_funcs);
 	if (conn)
 		conn->fd = fd;
 	else
@@ -1678,6 +1713,13 @@ static void accept_connection(int sock)
 }
 #endif
 
+struct interface_funcs socket_funcs = {
+	.write = writefd,
+	.read = readfd,
+	.can_write = socket_can_write,
+	.can_read = socket_can_read,
+};
+
 static int tdb_flags;
 
 /* We create initial nodes manually. */
@@ -2280,47 +2322,19 @@ int main(int argc, char *argv[])
 			if (&next->list != &connections)
 				talloc_increase_ref_count(next);
 
-			if (conn->domain) {
-				if (domain_can_read(conn))
-					handle_input(conn);
-				if (talloc_free(conn) == 0)
-					continue;
-
-				talloc_increase_ref_count(conn);
-				if (domain_can_write(conn) &&
-				    !list_empty(&conn->out_list))
-					handle_output(conn);
-				if (talloc_free(conn) == 0)
-					continue;
-			} else {
-				if (conn->pollfd_idx != -1) {
-					if (fds[conn->pollfd_idx].revents
-					    & ~(POLLIN|POLLOUT))
-						talloc_free(conn);
-					else if ((fds[conn->pollfd_idx].revents
-						  & POLLIN) &&
-						 !conn->is_ignored)
-						handle_input(conn);
-				}
-				if (talloc_free(conn) == 0)
-					continue;
-
-				talloc_increase_ref_count(conn);
-
-				if (conn->pollfd_idx != -1) {
-					if (fds[conn->pollfd_idx].revents
-					    & ~(POLLIN|POLLOUT))
-						talloc_free(conn);
-					else if ((fds[conn->pollfd_idx].revents
-						  & POLLOUT) &&
-						 !conn->is_ignored)
-						handle_output(conn);
-				}
-				if (talloc_free(conn) == 0)
-					continue;
+			if (conn->funcs->can_read(conn))
+				handle_input(conn);
+			if (talloc_free(conn) == 0)
+				continue;
 
-				conn->pollfd_idx = -1;
-			}
+			talloc_increase_ref_count(conn);
+
+			if (conn->funcs->can_write(conn))
+				handle_output(conn);
+			if (talloc_free(conn) == 0)
+				continue;
+
+			conn->pollfd_idx = -1;
 		}
 
 		if (delayed_requests) {
diff --git a/tools/xenstore/xenstored_core.h b/tools/xenstore/xenstored_core.h
index 589699e833..84b364d82c 100644
--- a/tools/xenstore/xenstored_core.h
+++ b/tools/xenstore/xenstored_core.h
@@ -87,8 +87,13 @@ struct delayed_request {
 };
 
 struct connection;
-typedef int connwritefn_t(struct connection *, const void *, unsigned int);
-typedef int connreadfn_t(struct connection *, void *, unsigned int);
+
+struct interface_funcs {
+	int (*write)(struct connection *, const void *, unsigned int);
+	int (*read)(struct connection *, void *, unsigned int);
+	bool (*can_write)(struct connection *);
+	bool (*can_read)(struct connection *);
+};
 
 struct connection
 {
@@ -132,9 +137,8 @@ struct connection
 	/* My watches. */
 	struct list_head watches;
 
-	/* Methods for communicating over this connection: write can be NULL */
-	connwritefn_t *write;
-	connreadfn_t *read;
+	/* Methods for communicating over this connection. */
+	struct interface_funcs *funcs;
 
 	/* Support for live update: connection id. */
 	unsigned int conn_id;
@@ -197,7 +201,7 @@ int write_node_raw(struct connection *conn, TDB_DATA *key, struct node *node,
 struct node *read_node(struct connection *conn, const void *ctx,
 		       const char *name);
 
-struct connection *new_connection(connwritefn_t *write, connreadfn_t *read);
+struct connection *new_connection(struct interface_funcs *funcs);
 struct connection *get_connection_by_id(unsigned int conn_id);
 void check_store(void);
 void corrupt(struct connection *conn, const char *fmt, ...);
diff --git a/tools/xenstore/xenstored_domain.c b/tools/xenstore/xenstored_domain.c
index 3d4d0649a2..04f2a974e4 100644
--- a/tools/xenstore/xenstored_domain.c
+++ b/tools/xenstore/xenstored_domain.c
@@ -172,6 +172,13 @@ static int readchn(struct connection *conn, void *data, unsigned int len)
 	return len;
 }
 
+static struct interface_funcs domain_funcs = {
+	.write = writechn,
+	.read = readchn,
+	.can_write = domain_can_write,
+	.can_read = domain_can_read,
+};
+
 static void *map_interface(domid_t domid)
 {
 	return xengnttab_map_grant_ref(*xgt_handle, domid,
@@ -389,7 +396,7 @@ static int new_domain(struct domain *domain, int port, bool restore)
 
 	domain->introduced = true;
 
-	domain->conn = new_connection(writechn, readchn);
+	domain->conn = new_connection(&domain_funcs);
 	if (!domain->conn)  {
 		errno = ENOMEM;
 		return errno;
@@ -1288,7 +1295,7 @@ void read_state_connection(const void *ctx, const void *state)
 	struct domain *domain, *tdomain;
 
 	if (sc->conn_type == XS_STATE_CONN_TYPE_SOCKET) {
-		conn = new_connection(writefd, readfd);
+		conn = new_connection(&socket_funcs);
 		if (!conn)
 			barf("error restoring connection");
 		conn->fd = sc->spec.socket_fd;
-- 
2.26.2



  reply	other threads:[~2021-01-22  9:23 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-22  9:23 [PATCH RFC 0/4] tools/xenstore: start of rework of xenstored Juergen Gross
2021-01-22  9:23 ` Juergen Gross [this message]
2021-01-22  9:23 ` [PATCH RFC 2/4] tools/xenstore: claim resources when running as daemon Juergen Gross
2021-01-22  9:23 ` [PATCH RFC 3/4] tools/xenstore: rework hashtable interfaces Juergen Gross
2021-01-22  9:23 ` [PATCH RFC 4/4] tools/xenstore: drop use of tdb Juergen Gross

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