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>
diff --git a/drivers/gpu/drm/i915/gvt/scheduler.c b/drivers/gpu/drm/i915/gvt/scheduler.c
index 7d87c43..f898df3 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 @@ 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));