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Re: [libvirt] [PATCH] vircommand: fix polling in virCommandProcessIO

On Tue, Apr 21, 2015 at 08:19:45PM +0300, Roman Bogorodskiy wrote:
When running on FreeBSD, there's a bug in virCommandProcessIO
polling that is triggered by the commandtest.

A test that triggers EPIPE in commandtest (named "test20") hungs
forever on FreeBSD.

Apparently, this happens because FreeBSD sets POLLHUP flag on revents
when stdin in closed. And as the current implementation only checks for
POLLOUT and POLLERR, it ends up looping forever inside
virCommandProcessIO and not trying to do one more write() that would
trigger EPIPE.

To fix that check for the POLLHUP flag along with POLLOUT and POLLERR.

We're already checking that for the pipe heading the other way and
according to information I found it makes sense to do this, even
though it seems that according to documentation this shouldn't happen.


src/util/vircommand.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/util/vircommand.c b/src/util/vircommand.c
index 648f5ed..f9b3c3f 100644
--- a/src/util/vircommand.c
+++ b/src/util/vircommand.c
@@ -2097,7 +2097,7 @@ virCommandProcessIO(virCommandPtr cmd)

-            if (fds[i].revents & (POLLOUT | POLLERR) &&
+            if (fds[i].revents & (POLLOUT | POLLHUP | POLLERR) &&
                fds[i].fd == cmd->inpipe) {
                int done;


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