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Commit 90d27a1b authored by Pei Zhang's avatar Pei Zhang Committed by Zhenyu Wang
Browse files

drm/i915/gvt: fix deadlock in workload_thread 



It's a classical abba type deadlock when using 2 mutex objects, which
are gvt.lock(a) and drm.struct_mutex(b). Deadlock happens in threads:
1. intel_gvt_create/destroy_vgpu: P(a)->P(b)
2. workload_thread: P(b)->P(a)

Fix solution is align the lock acquire sequence in both threads. This
patch choose to adjust the sequence in workload_thread function.

This fixed lockup symptom for guest-reboot stress test.

v2: adjust sequence in workload_thread based on zhenyu's suggestion.
    adjust sequence in create/destroy_vgpu function.
v3: fix to still require struct_mutex for dispatch_workload()

Signed-off-by: default avatarPei Zhang <pei.zhang@intel.com>
[zhenyuw: fix unused variables warnings.]
Signed-off-by: default avatarZhenyu Wang <zhenyuw@linux.intel.com>
parent 8be8f4a9

drivers/gpu/drm/i915/gvt/scheduler.c

+13 −20
Original line number Diff line number Diff line
@@ -160,8 +160,6 @@ static int shadow_context_status_change(struct notifier_block *nb, 


static int dispatch_workload(struct intel_vgpu_workload *workload)

{

	struct intel_vgpu *vgpu = workload->vgpu;

	struct intel_gvt *gvt = vgpu->gvt;

	int ring_id = workload->ring_id;

	struct i915_gem_context *shadow_ctx = workload->vgpu->shadow_ctx;

	struct drm_i915_private *dev_priv = workload->vgpu->gvt->dev_priv;
@@ -174,6 +172,8 @@ static int dispatch_workload(struct intel_vgpu_workload *workload) 
	shadow_ctx->desc_template = workload->ctx_desc.addressing_mode <<

				    GEN8_CTX_ADDRESSING_MODE_SHIFT;



	mutex_lock(&dev_priv->drm.struct_mutex);



	rq = i915_gem_request_alloc(dev_priv->engine[ring_id], shadow_ctx);

	if (IS_ERR(rq)) {

		gvt_err("fail to allocate gem request\n");
@@ -185,40 +185,35 @@ static int dispatch_workload(struct intel_vgpu_workload *workload) 


	workload->req = i915_gem_request_get(rq);



	mutex_lock(&gvt->lock);



	ret = intel_gvt_scan_and_shadow_workload(workload);

	if (ret)

		goto err;

		goto out;



	ret = intel_gvt_scan_and_shadow_wa_ctx(&workload->wa_ctx);

	if (ret)

		goto err;

		goto out;



	ret = populate_shadow_context(workload);

	if (ret)

		goto err;

		goto out;



	if (workload->prepare) {

		ret = workload->prepare(workload);

		if (ret)

			goto err;

			goto out;

	}



	mutex_unlock(&gvt->lock);



	gvt_dbg_sched("ring id %d submit workload to i915 %p\n",

			ring_id, workload->req);



	i915_add_request_no_flush(rq);

	ret = 0;

	workload->dispatched = true;

	return 0;

err:

out:

	if (ret)

		workload->status = ret;



	mutex_unlock(&gvt->lock);



	i915_add_request_no_flush(rq);

	mutex_unlock(&dev_priv->drm.struct_mutex);

	return ret;

}
@@ -438,9 +433,9 @@ static int workload_thread(void *priv) 
			intel_uncore_forcewake_get(gvt->dev_priv,

					FORCEWAKE_ALL);



		mutex_lock(&gvt->dev_priv->drm.struct_mutex);

		mutex_lock(&gvt->lock);

		ret = dispatch_workload(workload);

		mutex_unlock(&gvt->dev_priv->drm.struct_mutex);

		mutex_unlock(&gvt->lock);



		if (ret) {

			gvt_err("fail to dispatch workload, skip\n");
@@ -463,9 +458,7 @@ static int workload_thread(void *priv) 
		gvt_dbg_sched("will complete workload %p\n, status: %d\n",

				workload, workload->status);



		mutex_lock(&gvt->dev_priv->drm.struct_mutex);

		complete_current_workload(gvt, ring_id);

		mutex_unlock(&gvt->dev_priv->drm.struct_mutex);



		i915_gem_request_put(fetch_and_zero(&workload->req));