drm/i915: Remove stallcheck special handling, v3.

Both intel_unpin_work.pending and intel_unpin_work.enable_stall_check
were used to see if work should be enabled. By only using pending
some special cases are gone, and access to unpin_work can be simplified.

A flip could previously be queued before
stallcheck was active. With the addition of the pending member
enable_stall_check became obsolete and can thus be removed.

Use this to only access work members untilintel_mark_page_flip_active
is called, or intel_queue_mmio_flip is used. This will prevent
use-after-free, and makes it easier to verify accesses.

Changes since v1:
- Reword commit message.
- Do not access unpin_work after intel_mark_page_flip_active.
- Add the right memory barriers.
Changes since v2:
- atomic_read() needs a full smp_rmb.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1463490484-19540-3-git-send-email-maarten.lankhorst@linux.intel.com
Reviewed-by: Patrik Jakobsson <patrik.jakobsson@linux.intel.com>

1 files changed, 6 insertions, 5 deletions

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 24f4105..f23b119 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -615,9 +615,14 @@ static int i915_gem_pageflip_info(struct seq_file *m, void *data)
 			seq_printf(m, "No flip due on pipe %c (plane %c)\n",
 				   pipe, plane);
 		} else {
+			u32 pending;
 			u32 addr;
 
-			if (atomic_read(&work->pending) < INTEL_FLIP_COMPLETE) {
+			pending = atomic_read(&work->pending);
+			if (pending == INTEL_FLIP_INACTIVE) {
+				seq_printf(m, "Flip ioctl preparing on pipe %c (plane %c)\n",
+					   pipe, plane);
+			} else if (pending >= INTEL_FLIP_COMPLETE) {
 				seq_printf(m, "Flip queued on pipe %c (plane %c)\n",
 					   pipe, plane);
 			} else {
@@ -639,10 +644,6 @@ static int i915_gem_pageflip_info(struct seq_file *m, void *data)
 				   work->flip_queued_vblank,
 				   work->flip_ready_vblank,
 				   drm_crtc_vblank_count(&crtc->base));
-			if (work->enable_stall_check)
-				seq_puts(m, "Stall check enabled, ");
-			else
-				seq_puts(m, "Stall check waiting for page flip ioctl, ");
 			seq_printf(m, "%d prepares\n", atomic_read(&work->pending));
 
 			if (INTEL_INFO(dev)->gen >= 4)