commit c9b75c7bd7036a6895bbc3eba2ed0369238ebab4
from: Stefan Sperling <stsp@stsp.name>
date: Thu May 19 07:31:57 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 - 2ab714554f1fd2273c9705450cf192dabb4f6b9d
commit + c9b75c7bd7036a6895bbc3eba2ed0369238ebab4
blob - 135b8b683601bf61cba1c6e83ed9d36da871f90d
blob + 782f94ad26528e54d59fa5855bd1a0a4f674588b
--- lib/privsep.c
+++ lib/privsep.c
@@ -94,15 +94,9 @@ 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) {