[libvirt] [PATCH] virCommand: Properly handle POLLHUP

[Michal Privoznik]

It is a good practise to set revents to zero before doing any poll().
Moreover, we should check if event we waited for really occurred or
if any of fds we were polling on didn't encountered hangup.
---
 src/util/command.c |   21 +++++++++++++++++----
 1 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/util/command.c b/src/util/command.c
index f5effdf..9b553f0 100644
--- a/src/util/command.c
+++ b/src/util/command.c
@@ -1620,16 +1620,19 @@ virCommandProcessIO(virCommandPtr cmd)
         if (infd != -1) {
             fds[nfds].fd = infd;
             fds[nfds].events = POLLOUT;
+            fds[nfds].revents = 0;
             nfds++;
         }
         if (outfd != -1) {
             fds[nfds].fd = outfd;
             fds[nfds].events = POLLIN;
+            fds[nfds].revents = 0;
             nfds++;
         }
         if (errfd != -1) {
             fds[nfds].fd = errfd;
             fds[nfds].events = POLLIN;
+            fds[nfds].revents = 0;
             nfds++;
         }
 
@@ -1645,8 +1648,8 @@ virCommandProcessIO(virCommandPtr cmd)
         }
 
         for (i = 0; i < nfds ; i++) {
-            if (fds[i].fd == errfd ||
-                fds[i].fd == outfd) {
+            if (fds[i].revents & POLLIN &&
+                (fds[i].fd == errfd || fds[i].fd == outfd)) {
                 char data[1024];
                 char **buf;
                 size_t *len;
@@ -1684,7 +1687,7 @@ virCommandProcessIO(virCommandPtr cmd)
                     memcpy(*buf + *len, data, done);
                     *len += done;
                 }
-            } else {
+            } else if (fds[i].revents & POLLOUT) {
                 int done;
 
                 /* Coverity 5.3.0 can't see that we only get here if
@@ -1708,8 +1711,18 @@ virCommandProcessIO(virCommandPtr cmd)
                             VIR_DEBUG("ignoring failed close on fd %d", tmpfd);
                     }
                 }
+            } else if (fds[i].revents & POLLHUP) {
+                if (fds[i].fd == errfd) {
+                    VIR_DEBUG("hangup on stderr");
+                    errfd = -1;
+                } else if (fds[i].fd == outfd) {
+                    VIR_DEBUG("hangup on stdout");
+                    outfd = -1;
+                } else {
+                    VIR_DEBUG("hangup on stdin");
+                    infd = -1;
+                }
             }
-
         }
     }
 
-- 
1.7.3.4