klibc - Jun 2023 - [klibc:master] ipconfig: Do not poll sockets we don't intend to read from

Commit-ID:  b7316c5cc1a6b272bbba84c9f93aa49a1e7efb0e
Gitweb:    
http://git.kernel.org/?p=libs/klibc/klibc.git;a=commit;h=b7316c5cc1a6b272bbba84c9f93aa49a1e7efb0e
Author:     Ben Hutchings <ben at decadent.org.uk>
AuthorDate: Sun, 4 Jun 2023 23:42:12 +0200
Committer:  Ben Hutchings <ben at decadent.org.uk>
CommitDate: Mon, 5 Jun 2023 01:22:33 +0200

[klibc] ipconfig: Do not poll sockets we don't intend to read from

When a device is in state DEVST_COMPLETE or DEVST_ERROR, we never read
packets from its socket, but we still poll it.  If the socket is
readable or in an error state, this results in busy-polling until a
timeout is reached.

Only add a device's socket to the fds array when the device is in some
other state.

Signed-off-by: Ben Hutchings <ben at decadent.org.uk>

---
 usr/kinit/ipconfig/main.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/usr/kinit/ipconfig/main.c b/usr/kinit/ipconfig/main.c
index 5472d0f0..32e3dd1f 100644
--- a/usr/kinit/ipconfig/main.c
+++ b/usr/kinit/ipconfig/main.c
@@ -417,11 +417,14 @@ static int do_pkt_recv(int nr, struct pollfd *fds, time_t
now)
 	int i, ret = 0;
 	struct state *s;
 
-	for (i = 0, s = slist; s && nr; s = s->next, i++) {
+	for (i = 0, s = slist; s && nr; s = s->next) {
+		if (s->dev->pkt_fd != fds[i].fd)
+			continue;
 		if (fds[i].revents & POLLRDNORM) {
 			ret |= process_receive_event(s, now);
 			nr--;
 		}
+		i++;
 	}
 	return ret;
 }
@@ -452,12 +455,9 @@ static int loop(void)
 		int timeout_ms;
 		int x;
 
-		for (i = 0, s = slist; s; s = s->next, i++) {
+		for (i = 0, s = slist; s; s = s->next) {
 			dprintf("%s: state = %d\n", s->dev->name, s->state);
 
-			fds[i].fd = s->dev->pkt_fd;
-			fds[i].events = POLLRDNORM;
-
 			if (s->state == DEVST_COMPLETE) {
 				done++;
 				continue;
@@ -470,6 +470,12 @@ static int loop(void)
 				process_timeout_event(s, now.tv_sec);
 			}
 
+			if (s->state != DEVST_ERROR) {
+				fds[i].fd = s->dev->pkt_fd;
+				fds[i].events = POLLRDNORM;
+				i++;
+			}
+
 			if (timeout > s->expire - now.tv_sec)
 				timeout = s->expire - now.tv_sec;
 		}
@@ -485,7 +491,7 @@ static int loop(void)
 			if (timeout_ms <= 0)
 				timeout_ms = 100;
 
-			nr = poll(fds, n_devices, timeout_ms);
+			nr = poll(fds, i, timeout_ms);
 			prev = now;
 			gettimeofday(&now, NULL);