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>

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 24f4105..f23b119 100644 (file)
--- 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)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index bcf7cfc..a591f2a 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -3813,8 +3813,6 @@ static void page_flip_completed(struct intel_crtc *intel_crtc)
        struct drm_i915_private *dev_priv = to_i915(intel_crtc->base.dev);
        struct intel_unpin_work *work = intel_crtc->unpin_work;
 
-       /* ensure that the unpin work is consistent wrt ->pending. */
-       smp_rmb();
        intel_crtc->unpin_work = NULL;
 
        if (work->event)
@@ -10890,16 +10888,13 @@ static void do_intel_finish_page_flip(struct drm_i915_private *dev_priv,
        spin_lock_irqsave(&dev->event_lock, flags);
        work = intel_crtc->unpin_work;
 
-       /* Ensure we don't miss a work->pending update ... */
-       smp_rmb();
+       if (work && atomic_read(&work->pending) >= INTEL_FLIP_COMPLETE) {
+               /* ensure that the unpin work is consistent wrt ->pending. */
+               smp_rmb();
 
-       if (work == NULL || atomic_read(&work->pending) < INTEL_FLIP_COMPLETE) {
-               spin_unlock_irqrestore(&dev->event_lock, flags);
-               return;
+               page_flip_completed(intel_crtc);
        }
 
-       page_flip_completed(intel_crtc);
-
        spin_unlock_irqrestore(&dev->event_lock, flags);
 }
 
@@ -10995,10 +10990,8 @@ void intel_prepare_page_flip(struct drm_i915_private *dev_priv, int plane)
 static inline void intel_mark_page_flip_active(struct intel_unpin_work *work)
 {
        /* Ensure that the work item is consistent when activating it ... */
-       smp_wmb();
+       smp_mb__before_atomic();
        atomic_set(&work->pending, INTEL_FLIP_PENDING);
-       /* and that it is marked active as soon as the irq could fire. */
-       smp_wmb();
 }
 
 static int intel_gen2_queue_flip(struct drm_device *dev,
@@ -11032,7 +11025,6 @@ static int intel_gen2_queue_flip(struct drm_device *dev,
        intel_ring_emit(engine, intel_crtc->unpin_work->gtt_offset);
        intel_ring_emit(engine, 0); /* aux display base address, unused */
 
-       intel_mark_page_flip_active(intel_crtc->unpin_work);
        return 0;
 }
 
@@ -11064,7 +11056,6 @@ static int intel_gen3_queue_flip(struct drm_device *dev,
        intel_ring_emit(engine, intel_crtc->unpin_work->gtt_offset);
        intel_ring_emit(engine, MI_NOOP);
 
-       intel_mark_page_flip_active(intel_crtc->unpin_work);
        return 0;
 }
 
@@ -11103,7 +11094,6 @@ static int intel_gen4_queue_flip(struct drm_device *dev,
        pipesrc = I915_READ(PIPESRC(intel_crtc->pipe)) & 0x0fff0fff;
        intel_ring_emit(engine, pf | pipesrc);
 
-       intel_mark_page_flip_active(intel_crtc->unpin_work);
        return 0;
 }
 
@@ -11139,7 +11129,6 @@ static int intel_gen6_queue_flip(struct drm_device *dev,
        pipesrc = I915_READ(PIPESRC(intel_crtc->pipe)) & 0x0fff0fff;
        intel_ring_emit(engine, pf | pipesrc);
 
-       intel_mark_page_flip_active(intel_crtc->unpin_work);
        return 0;
 }
 
@@ -11234,7 +11223,6 @@ static int intel_gen7_queue_flip(struct drm_device *dev,
        intel_ring_emit(engine, intel_crtc->unpin_work->gtt_offset);
        intel_ring_emit(engine, (MI_NOOP));
 
-       intel_mark_page_flip_active(intel_crtc->unpin_work);
        return 0;
 }
 
@@ -11361,8 +11349,6 @@ static void intel_do_mmio_flip(struct intel_mmio_flip *mmio_flip)
        if (work == NULL)
                return;
 
-       intel_mark_page_flip_active(work);
-
        intel_pipe_update_start(crtc);
 
        if (INTEL_INFO(mmio_flip->i915)->gen >= 9)
@@ -11372,6 +11358,8 @@ static void intel_do_mmio_flip(struct intel_mmio_flip *mmio_flip)
                ilk_do_mmio_flip(crtc, work);
 
        intel_pipe_update_end(crtc);
+
+       intel_mark_page_flip_active(work);
 }
 
 static void intel_mmio_flip_work_func(struct work_struct *work)
@@ -11437,15 +11425,14 @@ static bool __intel_pageflip_stall_check(struct drm_device *dev,
        struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
        struct intel_unpin_work *work = intel_crtc->unpin_work;
        u32 addr;
+       u32 pending;
 
-       if (atomic_read(&work->pending) >= INTEL_FLIP_COMPLETE)
-               return true;
-
-       if (atomic_read(&work->pending) < INTEL_FLIP_PENDING)
-               return false;
+       pending = atomic_read(&work->pending);
+       /* ensure that the unpin work is consistent wrt ->pending. */
+       smp_rmb();
 
-       if (!work->enable_stall_check)
-               return false;
+       if (pending != INTEL_FLIP_PENDING)
+               return pending == INTEL_FLIP_COMPLETE;
 
        if (work->flip_ready_vblank == 0) {
                if (work->flip_queued_req &&
@@ -11626,6 +11613,11 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
         */
        if (!mmio_flip) {
                ret = i915_gem_object_sync(obj, engine, &request);
+               if (!ret && !request) {
+                       request = i915_gem_request_alloc(engine, NULL);
+                       ret = PTR_ERR_OR_ZERO(request);
+               }
+
                if (ret)
                        goto cleanup_pending;
        }
@@ -11639,36 +11631,29 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
        work->gtt_offset += intel_crtc->dspaddr_offset;
 
        if (mmio_flip) {
-               ret = intel_queue_mmio_flip(dev, crtc, obj);
-               if (ret)
-                       goto cleanup_unpin;
+               work->flip_queued_vblank = drm_crtc_vblank_count(crtc);
 
                i915_gem_request_assign(&work->flip_queued_req,
                                        obj->last_write_req);
-       } else {
-               if (!request) {
-                       request = i915_gem_request_alloc(engine, NULL);
-                       if (IS_ERR(request)) {
-                               ret = PTR_ERR(request);
-                               goto cleanup_unpin;
-                       }
-               }
 
+               ret = intel_queue_mmio_flip(dev, crtc, obj);
+               if (ret)
+                       goto cleanup_unpin;
+       } else {
                ret = dev_priv->display.queue_flip(dev, crtc, fb, obj, request,
                                                   page_flip_flags);
                if (ret)
                        goto cleanup_unpin;
 
                i915_gem_request_assign(&work->flip_queued_req, request);
-       }
 
-       if (request)
-               i915_add_request_no_flush(request);
+               work->flip_queued_vblank = drm_crtc_vblank_count(crtc);
+               intel_mark_page_flip_active(work);
 
-       work->flip_queued_vblank = drm_crtc_vblank_count(crtc);
-       work->enable_stall_check = true;
+               i915_add_request_no_flush(request);
+       }
 
-       i915_gem_track_fb(intel_fb_obj(work->old_fb), obj,
+       i915_gem_track_fb(intel_fb_obj(old_fb), obj,
                          to_intel_plane(primary)->frontbuffer_bit);
        mutex_unlock(&dev->struct_mutex);
 

diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 3536292..afde6a1 100644 (file)
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -992,7 +992,6 @@ struct intel_unpin_work {
        struct drm_i915_gem_request *flip_queued_req;
        u32 flip_queued_vblank;
        u32 flip_ready_vblank;
-       bool enable_stall_check;
 };
 
 struct intel_load_detect_pipe {