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Commit 312c4ba1 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Protect i915_active iterators from the shrinker 



If we allocate while iterating the rbtree of active nodes, we may hit
the shrinker and so retire the i915_active, reaping the rbtree. Modifying
the rbtree as we iterate is not good behaviour, so acquire the
i915_active first to keep the tree intact whenever we allocate.

Fixes: a42375af ("drm/i915: Release the active tracker tree upon idling")
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190208134704.23039-1-chris@chris-wilson.co.uk


Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
parent c10c78ad

drivers/gpu/drm/i915/i915_active.c

+25 −11
Original line number Diff line number Diff line
@@ -163,17 +163,25 @@ int i915_active_ref(struct i915_active *ref, 
		    struct i915_request *rq)

{

	struct i915_active_request *active;

	int err = 0;



	/* Prevent reaping in case we malloc/wait while building the tree */

	i915_active_acquire(ref);



	active = active_instance(ref, timeline);

	if (IS_ERR(active))

		return PTR_ERR(active);

	if (IS_ERR(active)) {

		err = PTR_ERR(active);

		goto out;

	}



	if (!i915_active_request_isset(active))

		ref->count++;

	__i915_active_request_set(active, rq);



	GEM_BUG_ON(!ref->count);

	return 0;

out:

	i915_active_release(ref);

	return err;

}



bool i915_active_acquire(struct i915_active *ref)
@@ -223,19 +231,25 @@ int i915_request_await_active_request(struct i915_request *rq, 
int i915_request_await_active(struct i915_request *rq, struct i915_active *ref)

{

	struct active_node *it, *n;

	int ret;

	int err = 0;



	ret = i915_request_await_active_request(rq, &ref->last);

	if (ret)

		return ret;

	/* await allocates and so we need to avoid hitting the shrinker */

	if (i915_active_acquire(ref))

		goto out; /* was idle */



	err = i915_request_await_active_request(rq, &ref->last);

	if (err)

		goto out;



	rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {

		ret = i915_request_await_active_request(rq, &it->base);

		if (ret)

			return ret;

		err = i915_request_await_active_request(rq, &it->base);

		if (err)

			goto out;

	}



	return 0;

out:

	i915_active_release(ref);

	return err;

}



#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)