[libvirt] [PATCH] virCommand: Properly handle POLLHUP
Eric Blake
eblake at redhat.com
Tue Jan 3 19:00:23 UTC 2012
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(-)
>
> 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;
Oh my - you're right - we stack-allocated struct pollfd fds[3]; without
initialization earlier on.
> @@ -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;
> + }
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.
--
Eric Blake eblake at redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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