From 330c422a8ee88d77407f65494f3bbf141a8d9453 Mon Sep 17 00:00:00 2001
From: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Date: Tue, 20 Jun 2017 13:57:06 -0400
Subject: [PATCH] drm/core: Fail atomic IOCTL with no CRTC state but with signaling.
Git-commit: 330c422a8ee88d77407f65494f3bbf141a8d9453
Patch-mainline: v4.14-rc1
References: FATE#322643 bsc#1055900
Problem : While running IGT kms_atomic_transition test suite i encountered
a hang in drmHandleEvent immediately following an atomic_commit.
After dumping the atomic state I relized that in this case there was
not even one CRTC attached to the state and only disabled
planes. This probably due to a commit which hadn't changed any property
which would require attaching crtc state. This means drmHandleEvent
will never wake up from read since without CRTC in atomic state
the event fd will not be signaled.
Fix: Protect against this issue by failing atomic_commit early in
drm_mode_atomic_commit where such probelm can be identified.
V2:
Fix typos and extra newlines.
Change-id: I3ee28ffae35fd1e8bfe553146c44da53da02e6f8
Signed-off-by: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1497981426-27203-1-git-send-email-Andrey.Grodzovsky@amd.com
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/gpu/drm/drm_atomic.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -2042,7 +2042,7 @@ static int prepare_crtc_signaling(struct
{
struct drm_crtc *crtc;
struct drm_crtc_state *crtc_state;
- int i, ret;
+ int i, c = 0, ret;
if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY)
return 0;
@@ -2103,8 +2103,17 @@ static int prepare_crtc_signaling(struct
crtc_state->event->base.fence = fence;
}
+
+ c++;
}
+ /*
+ * Having this flag means user mode pends on event which will never
+ * reach due to lack of at least one CRTC for signaling
+ */
+ if (c == 0 && (arg->flags & DRM_MODE_PAGE_FLIP_EVENT))
+ return -EINVAL;
+
return 0;
}