commit ff47022487821209766a1ed2b881c9584ba08120
from: Stefan Sperling <stsp@stsp.name>
via: Thomas Adam <thomas@xteddy.org>
date: Thu May 19 13:34:05 2022 UTC

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

imsg_read() will call recvmsg() on the file descriptor regardless
of the read buffer's state, so we should ensure that data is ready.
The read buffer is used by imsg_get(), not imsg_read().
We already call imsg_get() before imsg_read(), and call the latter
only if imsg_get() returns zero.

commit - 3e54812463cc8a33236c16a18d1361597e516d71
commit + ff47022487821209766a1ed2b881c9584ba08120
blob - d0da0d1326d22a856516386bcc38b06f9e55d415
blob + c0b028f2df10a4790b2d55637533cce65b42ab06
--- lib/privsep.c
+++ lib/privsep.c
@@ -93,15 +93,9 @@ read_imsg(struct imsgbuf *ibuf)
 	const struct got_error *err;
 	size_t n;
 
-	/*
-	 * 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;
-	}
+	err = poll_fd(ibuf->fd, POLLIN, INFTIM);
+	if (err)
+		return err;
 
 	n = imsg_read(ibuf);
 	if (n == -1) {