[PATCH xserver v2] xwayland: handle EAGAIN and EINTR gracefully

[Olivier Fourdan]

wl_display_flush() can fail with EAGAIN and Xwayland would make this a
fatal error.

Handle the usual EAGAIN and EINTR gracefully so that Xwayland doesn't
die for so little.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1278159
Signed-off-by: Olivier Fourdan <ofourdan at redhat.com>
---
 v2: oops, need to poll() on EAGAIN between retries

 hw/xwayland/xwayland.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/hw/xwayland/xwayland.c b/hw/xwayland/xwayland.c
index 847321e..2c7f45b 100644
--- a/hw/xwayland/xwayland.c
+++ b/hw/xwayland/xwayland.c
@@ -33,6 +33,7 @@
 #include <compositeext.h>
 #include <glx_extinit.h>
 #include <os.h>
+#include <xserver_poll.h>
 
 #ifdef XF86VIDMODE
 #include <X11/extensions/xf86vmproto.h>
@@ -481,6 +482,23 @@ xwl_read_events (struct xwl_screen *xwl_screen)
         FatalError("failed to dispatch Wayland events: %s\n", strerror(errno));
 }
 
+static Bool
+xwl_poll_display_fd (struct xwl_screen *xwl_screen)
+{
+    struct pollfd poll_fd;
+    int ret;
+
+    poll_fd.fd = wl_display_get_fd(xwl_screen->display);
+    poll_fd.events = POLLOUT;
+    do {
+        ret = xserver_poll(&poll_fd, 1, -1);
+        if (ret > 0)
+            return TRUE;
+    } while (ret == -1 && (errno == EINTR || errno == EAGAIN));
+
+    return FALSE;
+ }
+
 static void
 xwl_dispatch_events (struct xwl_screen *xwl_screen)
 {
@@ -496,7 +514,12 @@ xwl_dispatch_events (struct xwl_screen *xwl_screen)
 
     xwl_screen->prepare_read = 1;
 
-    ret = wl_display_flush(xwl_screen->display);
+    do {
+        ret = wl_display_flush(xwl_screen->display);
+        if (ret == -1 && errno == EAGAIN && xwl_poll_display_fd(xwl_screen))
+            continue;
+    } while (ret == -1 && errno == EINTR);
+
     if (ret == -1)
         FatalError("failed to write to XWayland fd: %s\n", strerror(errno));
 }
-- 
2.9.3