mirror of https://gitee.com/openkylin/linux.git
drm: Mark up accesses of vblank->enabled outside of its spinlock
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@chris-wilson.co.uk> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/20170317202030.24410-1-chris@chris-wilson.co.uk Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
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@ -325,6 +325,8 @@ static void vblank_disable_and_save(struct drm_device *dev, unsigned int pipe)
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struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
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unsigned long irqflags;
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assert_spin_locked(&dev->vbl_lock);
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/* Prevent vblank irq processing while disabling vblank irqs,
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* so no updates of timestamps or count can happen after we've
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* disabled. Needed to prevent races in case of delayed irq's.
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@ -336,10 +338,8 @@ static void vblank_disable_and_save(struct drm_device *dev, unsigned int pipe)
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* calling the ->disable_vblank() operation in atomic context with the
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* hardware potentially runtime suspended.
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*/
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if (vblank->enabled) {
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if (cmpxchg_relaxed(&vblank->enabled, true, false))
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__disable_vblank(dev, pipe);
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vblank->enabled = false;
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}
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/*
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* Always update the count and timestamp to maintain the
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@ -384,7 +384,7 @@ void drm_vblank_cleanup(struct drm_device *dev)
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for (pipe = 0; pipe < dev->num_crtcs; pipe++) {
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struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
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WARN_ON(vblank->enabled &&
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WARN_ON(READ_ONCE(vblank->enabled) &&
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drm_core_check_feature(dev, DRIVER_MODESET));
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del_timer_sync(&vblank->disable_timer);
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@ -1097,11 +1097,16 @@ static int drm_vblank_enable(struct drm_device *dev, unsigned int pipe)
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*/
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ret = __enable_vblank(dev, pipe);
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DRM_DEBUG("enabling vblank on crtc %u, ret: %d\n", pipe, ret);
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if (ret)
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if (ret) {
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atomic_dec(&vblank->refcount);
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else {
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vblank->enabled = true;
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} else {
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drm_update_vblank_count(dev, pipe, 0);
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/* drm_update_vblank_count() includes a wmb so we just
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* need to ensure that the compiler emits the write
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* to mark the vblank as enabled after the call
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* to drm_update_vblank_count().
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*/
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WRITE_ONCE(vblank->enabled, true);
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}
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}
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@ -1509,7 +1514,7 @@ static int drm_queue_vblank_event(struct drm_device *dev, unsigned int pipe,
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* vblank disable, so no need for further locking. The reference from
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* drm_vblank_get() protects against vblank disable from another source.
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*/
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if (!vblank->enabled) {
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if (!READ_ONCE(vblank->enabled)) {
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ret = -EINVAL;
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goto err_unlock;
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}
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@ -1636,7 +1641,7 @@ int drm_wait_vblank(struct drm_device *dev, void *data,
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DRM_WAIT_ON(ret, vblank->queue, 3 * HZ,
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(((drm_vblank_count(dev, pipe) -
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vblwait->request.sequence) <= (1 << 23)) ||
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!vblank->enabled ||
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!READ_ONCE(vblank->enabled) ||
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!dev->irq_enabled));
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}
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