libxl: react correctly to bootloader pty master POLLHUP

Receive POLLHUP on the bootloader master pty is not an error.
Hopefully it means that the bootloader has exited and therefore the
pty slave side has no process group any more.  (At least NetBSD
indicates POLLHUP on the master in this case.)

So send the bootloader SIGTERM; if it has already exited then this has
no effect (except that on some versions of NetBSD it erroneously
returns ESRCH and we print a harmless warning) and we will then
collect the bootloader's exit status and be satisfied.

However, we remember that we have done this so that if we got POLLHUP
for some other reason than that the bootloader exited we report
something resembling a useful message.

In order to implement this we need to provide a way for users of
datacopier to handle POLLHUP rather than treating it as fatal.

We rename bootloader_abort to bootloader_stop since it now no longer
only applies to error situations.

Signed-off-by: Roger Pau Monne <roger.pau@citrix.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/tools/libxl/libxl_aoutils.c b/tools/libxl/libxl_aoutils.c
index 99972a23b0..983a60afc7 100644
--- a/tools/libxl/libxl_aoutils.c
+++ b/tools/libxl/libxl_aoutils.c
@@ -97,11 +97,31 @@ void libxl__datacopier_prefixdata(libxl__egc *egc, libxl__datacopier_state *dc,
     LIBXL_TAILQ_INSERT_TAIL(&dc->bufs, buf, entry);
 }
 
+static int datacopier_pollhup_handled(libxl__egc *egc,
+                                      libxl__datacopier_state *dc,
+                                      short revents, int onwrite)
+{
+    STATE_AO_GC(dc->ao);
+
+    if (dc->callback_pollhup && (revents & POLLHUP)) {
+        LOG(DEBUG, "received POLLHUP on %s during copy of %s",
+            onwrite ? dc->writewhat : dc->readwhat,
+            dc->copywhat);
+        libxl__datacopier_kill(dc);
+        dc->callback_pollhup(egc, dc, onwrite, -1);
+        return 1;
+    }
+    return 0;
+}
+
 static void datacopier_readable(libxl__egc *egc, libxl__ev_fd *ev,
                                 int fd, short events, short revents) {
     libxl__datacopier_state *dc = CONTAINER_OF(ev, *dc, toread);
     STATE_AO_GC(dc->ao);
 
+    if (datacopier_pollhup_handled(egc, dc, revents, 0))
+        return;
+
     if (revents & ~POLLIN) {
         LOG(ERROR, "unexpected poll event 0x%x (should be POLLIN)"
             " on %s during copy of %s", revents, dc->readwhat, dc->copywhat);
@@ -163,6 +183,9 @@ static void datacopier_writable(libxl__egc *egc, libxl__ev_fd *ev,
     libxl__datacopier_state *dc = CONTAINER_OF(ev, *dc, towrite);
     STATE_AO_GC(dc->ao);
 
+    if (datacopier_pollhup_handled(egc, dc, revents, 1))
+        return;
+
     if (revents & ~POLLOUT) {
         LOG(ERROR, "unexpected poll event 0x%x (should be POLLOUT)"
             " on %s during copy of %s", revents, dc->writewhat, dc->copywhat);