Documentation/atomic_ops.txt tells us that there are memory
barriers optimized for atomic_inc and other atomic_t ops.
Use these instead of smp_wmb(), and also to make the required
memory barriers around vblank counter increments more explicit.
Signed-off-by: Mario Kleiner <mario.kleiner@xxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/drm_irq.c | 10 +++++++---
1 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 149805a..891bf6d 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -164,8 +164,10 @@ static void vblank_disable_and_save(struct drm_device *dev, int crtc)
* available. In that case we can't account for this and just
* hope for the best.
*/
- if ((vblrc > 0) && (abs64(diff_ns) > 1000000))
+ if ((vblrc > 0) && (abs64(diff_ns) > 1000000)) {
atomic_inc(&dev->_vblank_count[crtc]);
+ smp_mb__after_atomic_inc();
+ }
/* Invalidate all timestamps while vblank irq's are off. */
clear_vblank_timestamps(dev, crtc);
@@ -858,10 +860,11 @@ static void drm_update_vblank_count(struct drm_device *dev, int crtc)
if (rc) {
tslot = atomic_read(&dev->_vblank_count[crtc]) + diff;
vblanktimestamp(dev, crtc, tslot) = t_vblank;
- smp_wmb();
}
+ smp_mb__before_atomic_inc();
atomic_add(diff, &dev->_vblank_count[crtc]);
+ smp_mb__after_atomic_inc();
}
/**
@@ -1296,12 +1299,13 @@ void drm_handle_vblank(struct drm_device *dev, int crtc)
if (abs64(diff_ns) > DRM_REDUNDANT_VBLIRQ_THRESH_NS) {
/* Store new timestamp in ringbuffer. */
vblanktimestamp(dev, crtc, vblcount + 1) = tvblank;
- smp_wmb();
/* Increment cooked vblank count. This also atomically commits
* the timestamp computed above.
*/
+ smp_mb__before_atomic_inc();
atomic_inc(&dev->_vblank_count[crtc]);
+ smp_mb__after_atomic_inc();
} else {
DRM_DEBUG("crtc %d: Redundant vblirq ignored. diff_ns = %d\n",
crtc, (int) diff_ns);
--
1.7.1
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