From 90d27a1b180e51ef071350a302648b41fe884ff2 Mon Sep 17 00:00:00 2001 From: Pei Zhang Date: Mon, 14 Nov 2016 18:02:57 +0800 Subject: [PATCH] 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 [zhenyuw: fix unused variables warnings.] Signed-off-by: Zhenyu Wang --- drivers/gpu/drm/i915/gvt/scheduler.c | 33 +++++++++++----------------- 1 file changed, 13 insertions(+), 20 deletions(-) diff --git a/drivers/gpu/drm/i915/gvt/scheduler.c b/drivers/gpu/drm/i915/gvt/scheduler.c index 7d87c43661c5..f898df38dd9a 100644 --- a/drivers/gpu/drm/i915/gvt/scheduler.c +++ b/drivers/gpu/drm/i915/gvt/scheduler.c @@ -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: - workload->status = ret; - - mutex_unlock(&gvt->lock); +out: + if (ret) + workload->status = ret; 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 @@ complete: 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)); -- 2.20.1