From: Jan Pokorny <jpokorny@redhat.com>
Date: Tue, 13 Sep 2011 21:12:15 +0200
Subject: [PATCH 3/4] (bz732483) executils: add comments wrt. read_data() branches

Signed-off-by: Jan Pokorny <jpokorny@redhat.com>

--- a/ricci/common/executils.cpp
+++ b/ricci/common/executils.cpp
@@ -271,14 +271,21 @@
 			char data_in[4096];
 			int ret = read(fd, data_in, sizeof(data_in));
 			if (ret < 0)
+				// if it was errno==EINTR, POLLIN event will be kept, otherwise
+				// presumably cleared and problem indicated with POLLERR|POLNVAL
 				return;
 			if (ret == 0) {
+				// EOF;  it may be (without guarantees) accompanied with POLLHUP event
+				// upon current/next poll (see [1]), but handle this safely in any case
+				// [1] http://www.greenend.org.uk/rjk/2001/06/poll.html
 				close_fd(fd);
 				fd_closed = true;
 				return;
 			}
 			data.append(data_in, ret);
 			if (ret == sizeof(data_in))
+				// shortcut to ensure that no data are missed when POLLIN|POLLHUP
+				// and we haven't read all yet (POLLIN will remain set in such case)
 				return;
 		} catch ( ... ) {
 			close_fd(fd);