Order the update to vblank->enabled after the timestamp is primed so
that a concurrent unlocked reader will only see the vblank->enabled with
the current timestamp.
v2: vblank->enable is guarded by dev->vbl_lock not
dev->vblank_time_lock, update the READ_ONCE accordingly.
Do not add a READ_ONCE(vblank->enabled) inside the interrupt handler to
avoid missing an interrupt whilst racing with enable_vblank()
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
---
drivers/gpu/drm/drm_irq.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 53a526c7b24d..c47e07c89136 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -325,6 +325,8 @@ static void vblank_disable_and_save(struct drm_device *dev, unsigned int pipe)
struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
unsigned long irqflags;
+ assert_spin_locked(&dev->vbl_lock);
+
/* Prevent vblank irq processing while disabling vblank irqs,
* so no updates of timestamps or count can happen after we've
* disabled. Needed to prevent races in case of delayed irq's.
@@ -336,10 +338,8 @@ static void vblank_disable_and_save(struct drm_device *dev, unsigned int pipe)
* calling the ->disable_vblank() operation in atomic context with the
* hardware potentially runtime suspended.
*/
- if (vblank->enabled) {
+ if (cmpxchg_relaxed(&vblank->enabled, true, false))
__disable_vblank(dev, pipe);
- vblank->enabled = false;
- }
/*
* Always update the count and timestamp to maintain the
@@ -384,7 +384,7 @@ void drm_vblank_cleanup(struct drm_device *dev)
for (pipe = 0; pipe < dev->num_crtcs; pipe++) {
struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
- WARN_ON(vblank->enabled &&
+ WARN_ON(READ_ONCE(vblank->enabled) &&
drm_core_check_feature(dev, DRIVER_MODESET));
del_timer_sync(&vblank->disable_timer);
@@ -1105,11 +1105,16 @@ static int drm_vblank_enable(struct drm_device *dev, unsigned int pipe)
*/
ret = __enable_vblank(dev, pipe);
DRM_DEBUG("enabling vblank on crtc %u, ret: %d\n", pipe, ret);
- if (ret)
+ if (ret) {
atomic_dec(&vblank->refcount);
- else {
- vblank->enabled = true;
+ } else {
drm_update_vblank_count(dev, pipe, 0);
+ /* drm_update_vblank_count() includes a wmb so we just
+ * need to ensure that the compiler emits the write
+ * to mark the vblank as enabled after the call
+ * to drm_update_vblank_count().
+ */
+ WRITE_ONCE(vblank->enabled, true);
}
}
@@ -1517,7 +1522,7 @@ static int drm_queue_vblank_event(struct drm_device *dev, unsigned int pipe,
* vblank disable, so no need for further locking. The reference from
* drm_vblank_get() protects against vblank disable from another source.
*/
- if (!vblank->enabled) {
+ if (!READ_ONCE(vblank->enabled)) {
ret = -EINVAL;
goto err_unlock;
}
@@ -1644,7 +1649,7 @@ int drm_wait_vblank(struct drm_device *dev, void *data,
DRM_WAIT_ON(ret, vblank->queue, 3 * HZ,
(((drm_vblank_count(dev, pipe) -
vblwait->request.sequence) <= (1 << 23)) ||
- !vblank->enabled ||
+ !READ_ONCE(vblank->enabled) ||
!dev->irq_enabled));
}
--
2.11.0
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