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Commit 7ae19400 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Defer removing fence register tracking to rpm wakeup 



Currently, we may simultaneously release the fence register from both
fence_update() and i915_gem_restore_fences(). This is dangerous, so
defer the bookkeeping entirely to i915_gem_restore_fences() when the
device is asleep.

Reported-by: default avatarMika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: default avatarMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190208153708.20023-1-chris@chris-wilson.co.uk
parent 73a116be

drivers/gpu/drm/i915/i915_gem_fence_reg.c

+32 −30
Original line number Diff line number Diff line
@@ -210,6 +210,7 @@ static int fence_update(struct drm_i915_fence_reg *fence, 
			struct i915_vma *vma)

{

	intel_wakeref_t wakeref;

	struct i915_vma *old;

	int ret;



	if (vma) {
@@ -229,49 +230,55 @@ static int fence_update(struct drm_i915_fence_reg *fence, 
			return ret;

	}



	if (fence->vma) {

		struct i915_vma *old = fence->vma;



	old = xchg(&fence->vma, NULL);

	if (old) {

		ret = i915_active_request_retire(&old->last_fence,

					     &old->obj->base.dev->struct_mutex);

		if (ret)

		if (ret) {

			fence->vma = old;

			return ret;

		}



		i915_vma_flush_writes(old);

	}



	if (fence->vma && fence->vma != vma) {

		/* Ensure that all userspace CPU access is completed before

		/*

		 * Ensure that all userspace CPU access is completed before

		 * stealing the fence.

		 */

		GEM_BUG_ON(fence->vma->fence != fence);

		i915_vma_revoke_mmap(fence->vma);



		fence->vma->fence = NULL;

		fence->vma = NULL;

		if (old != vma) {

			GEM_BUG_ON(old->fence != fence);

			i915_vma_revoke_mmap(old);

			old->fence = NULL;

		}



		list_move(&fence->link, &fence->i915->mm.fence_list);

	}



	/* We only need to update the register itself if the device is awake.

	/*

	 * We only need to update the register itself if the device is awake.

	 * If the device is currently powered down, we will defer the write

	 * to the runtime resume, see i915_gem_restore_fences().

	 *

	 * This only works for removing the fence register, on acquisition

	 * the caller must hold the rpm wakeref. The fence register must

	 * be cleared before we can use any other fences to ensure that

	 * the new fences do not overlap the elided clears, confusing HW.

	 */

	wakeref = intel_runtime_pm_get_if_in_use(fence->i915);

	if (wakeref) {

		fence_write(fence, vma);

		intel_runtime_pm_put(fence->i915, wakeref);

	if (!wakeref) {

		GEM_BUG_ON(vma);

		return 0;

	}



	if (vma) {

		if (fence->vma != vma) {

			vma->fence = fence;

	fence_write(fence, vma);

	fence->vma = vma;

		}



	if (vma) {

		vma->fence = fence;

		list_move_tail(&fence->link, &fence->i915->mm.fence_list);

	}



	intel_runtime_pm_put(fence->i915, wakeref);

	return 0;

}
@@ -473,9 +480,10 @@ void i915_gem_restore_fences(struct drm_i915_private *dev_priv) 
{

	int i;



	rcu_read_lock(); /* keep obj alive as we dereference */

	for (i = 0; i < dev_priv->num_fence_regs; i++) {

		struct drm_i915_fence_reg *reg = &dev_priv->fence_regs[i];

		struct i915_vma *vma = reg->vma;

		struct i915_vma *vma = READ_ONCE(reg->vma);



		GEM_BUG_ON(vma && vma->fence != reg);
@@ -483,18 +491,12 @@ void i915_gem_restore_fences(struct drm_i915_private *dev_priv) 
		 * Commit delayed tiling changes if we have an object still

		 * attached to the fence, otherwise just clear the fence.

		 */

		if (vma && !i915_gem_object_is_tiled(vma->obj)) {

			GEM_BUG_ON(!reg->dirty);

			GEM_BUG_ON(i915_vma_has_userfault(vma));



			list_move(&reg->link, &dev_priv->mm.fence_list);

			vma->fence = NULL;

		if (vma && !i915_gem_object_is_tiled(vma->obj))

			vma = NULL;

		}



		fence_write(reg, vma);

		reg->vma = vma;

	}

	rcu_read_unlock();

}



/**