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: Pei Zhang <pei.zhang@intel.com> [zhenyuw: fix unused variables warnings.] Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
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@ -160,8 +160,6 @@ static int shadow_context_status_change(struct notifier_block *nb,
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static int dispatch_workload(struct intel_vgpu_workload *workload)
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{
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struct intel_vgpu *vgpu = workload->vgpu;
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struct intel_gvt *gvt = vgpu->gvt;
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int ring_id = workload->ring_id;
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struct i915_gem_context *shadow_ctx = workload->vgpu->shadow_ctx;
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struct drm_i915_private *dev_priv = workload->vgpu->gvt->dev_priv;
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@ -174,6 +172,8 @@ static int dispatch_workload(struct intel_vgpu_workload *workload)
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shadow_ctx->desc_template = workload->ctx_desc.addressing_mode <<
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GEN8_CTX_ADDRESSING_MODE_SHIFT;
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mutex_lock(&dev_priv->drm.struct_mutex);
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rq = i915_gem_request_alloc(dev_priv->engine[ring_id], shadow_ctx);
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if (IS_ERR(rq)) {
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gvt_err("fail to allocate gem request\n");
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@ -185,40 +185,35 @@ static int dispatch_workload(struct intel_vgpu_workload *workload)
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workload->req = i915_gem_request_get(rq);
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mutex_lock(&gvt->lock);
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ret = intel_gvt_scan_and_shadow_workload(workload);
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if (ret)
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goto err;
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goto out;
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ret = intel_gvt_scan_and_shadow_wa_ctx(&workload->wa_ctx);
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if (ret)
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goto err;
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goto out;
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ret = populate_shadow_context(workload);
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if (ret)
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goto err;
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goto out;
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if (workload->prepare) {
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ret = workload->prepare(workload);
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if (ret)
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goto err;
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goto out;
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}
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mutex_unlock(&gvt->lock);
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gvt_dbg_sched("ring id %d submit workload to i915 %p\n",
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ring_id, workload->req);
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i915_add_request_no_flush(rq);
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ret = 0;
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workload->dispatched = true;
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return 0;
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err:
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out:
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if (ret)
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workload->status = ret;
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mutex_unlock(&gvt->lock);
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i915_add_request_no_flush(rq);
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mutex_unlock(&dev_priv->drm.struct_mutex);
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return ret;
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}
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@ -438,9 +433,9 @@ static int workload_thread(void *priv)
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intel_uncore_forcewake_get(gvt->dev_priv,
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FORCEWAKE_ALL);
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mutex_lock(&gvt->dev_priv->drm.struct_mutex);
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mutex_lock(&gvt->lock);
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ret = dispatch_workload(workload);
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mutex_unlock(&gvt->dev_priv->drm.struct_mutex);
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mutex_unlock(&gvt->lock);
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if (ret) {
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gvt_err("fail to dispatch workload, skip\n");
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@ -463,9 +458,7 @@ complete:
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gvt_dbg_sched("will complete workload %p\n, status: %d\n",
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workload, workload->status);
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mutex_lock(&gvt->dev_priv->drm.struct_mutex);
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complete_current_workload(gvt, ring_id);
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mutex_unlock(&gvt->dev_priv->drm.struct_mutex);
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i915_gem_request_put(fetch_and_zero(&workload->req));
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