commit 3e54812463cc8a33236c16a18d1361597e516d71
from: Stefan Sperling <stsp@stsp.name>
via: Thomas Adam <thomas@xteddy.org>
date: Thu May 19 13:34:05 2022 UTC

Skip poll(2) if an imsgbuf has a non-empty read buffer.

commit - e9f1a409ccc66a6fb79a3022695ca78ad26972ea
commit + 3e54812463cc8a33236c16a18d1361597e516d71
blob - c0b028f2df10a4790b2d55637533cce65b42ab06
blob + d0da0d1326d22a856516386bcc38b06f9e55d415
--- lib/privsep.c
+++ lib/privsep.c
@@ -93,9 +93,15 @@ read_imsg(struct imsgbuf *ibuf)
 	const struct got_error *err;
 	size_t n;
 
-	err = poll_fd(ibuf->fd, POLLIN, INFTIM);
-	if (err)
-		return err;
+	/*
+	 * There is no imsg API function to tell us whether the
+	 * read buffer still contains pending data :-(
+	 */
+	if (ibuf->r.wpos < IMSG_HEADER_SIZE) {
+		err = poll_fd(ibuf->fd, POLLIN, INFTIM);
+		if (err)
+			return err;
+	}
 
 	n = imsg_read(ibuf);
 	if (n == -1) {