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Re: [libvirt] [PATCH] virCommand: Properly handle POLLHUP



On 03.01.2012 20:00, Eric Blake wrote:
> On 01/03/2012 10:58 AM, Michal Privoznik wrote:
>> 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.
> 
> Looks like this also solves:
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=770788
> 
>> ---
>>  src/util/command.c |   21 +++++++++++++++++----
>>  1 files changed, 17 insertions(+), 4 deletions(-)
>>

> Should we also be probing for POLLERR?  (POLLNVAL shouldn't ever be
> present, because it would indicate a bigger bug in our code).
> 
> ACK - what you have is a strict improvement, even if we further decide
> to check for POLLERR.
> 

Thanks, pushed with this squashed in:

diff --git a/src/util/command.c b/src/util/command.c
index 9b553f0..bdaa88b 100644
--- a/src/util/command.c
+++ b/src/util/command.c
@@ -1687,7 +1687,10 @@ virCommandProcessIO(virCommandPtr cmd)
                     memcpy(*buf + *len, data, done);
                     *len += done;
                 }
-            } else if (fds[i].revents & POLLOUT) {
+            }
+
+            if (fds[i].revents & POLLOUT &&
+                fds[i].fd == infd) {
                 int done;

                 /* Coverity 5.3.0 can't see that we only get here if
@@ -1711,7 +1714,9 @@ virCommandProcessIO(virCommandPtr cmd)
                             VIR_DEBUG("ignoring failed close on fd %d",
tmpfd);
                     }
                 }
-            } else if (fds[i].revents & POLLHUP) {
+            }
+
+            if (fds[i].revents & (POLLHUP | POLLERR)) {
                 if (fds[i].fd == errfd) {
                     VIR_DEBUG("hangup on stderr");
                     errfd = -1;


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