[PATCH 5/6] xfree86: Fix race condition failure opening drm.

[Bryce Harrington]

If other processes have had drm open previously, xserver may attempt to
open the device too early and fail, with xserver error exit "Cannot
run in framebuffer mode" or Xorg.0.log messages about "setversion 1.4
failed".

In this situation, we're receiving back -EACCES from libdrm.  To address
this we need to re-set ourselves as the drm master, and keep trying to
set the interface until it works (or until we give up).

See https://bugs.launchpad.net/ubuntu/+source/libdrm/+bug/982889

Signed-off-by: Bryce Harrington <bryce at canonical.com>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 hw/xfree86/os-support/linux/lnx_platform.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/hw/xfree86/os-support/linux/lnx_platform.c b/hw/xfree86/os-support/linux/lnx_platform.c
index 10c8ecf..977d590 100644
--- a/hw/xfree86/os-support/linux/lnx_platform.c
+++ b/hw/xfree86/os-support/linux/lnx_platform.c
@@ -43,8 +43,14 @@ get_drm_info(struct OdevAttributes *attribs, char *path)
 	    if (tries > 1)
 		LogMessage(X_INFO, "setversion 1.4 succeeded on try #%d\n", tries);
 	    break;
+	} else if (err != -EACCES) {
+	    break;
 	}
+
 	usleep(10000);
+
+	if (!drmSetMaster(fd))
+	    LogMessage(X_INFO, "drmSetMaster succeeded\n");
     }
     if (err) {
         ErrorF("setversion 1.4 failed: %s\n", strerror(-err));
-- 
1.7.9.5