[PATCH 05/10] drm/amdgpu: implement asynchronous userq destruction routine

[Zhu Lingshan <lingshan.zhu@amd.com>]

The last kref of a user queue may be released
from a context where can not sleep or
require an alrady hold lock(reset_domain->sem, reset_mutext, etc)
in the same context.

This commit helps resovle these issues by refactoring
the user queue destruction function to a deferred
work item, so it does not conflict with the caller context.

Signed-off-by: Zhu Lingshan <lingshan.zhu@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c | 15 ++++++++++++---
 drivers/gpu/drm/amd/amdgpu/amdgpu_userq.h |  7 +++++++
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
index f398986a61a5..9fe20cb9af58 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
@@ -596,11 +596,11 @@ amdgpu_userq_destroy(struct amdgpu_userq_mgr *uq_mgr, struct amdgpu_usermode_que
 	return r;
 }
 
-static void amdgpu_userq_kref_destroy(struct kref *kref)
+static void amdgpu_userq_destroy_worker(struct work_struct *work)
 {
 	int r;
 	struct amdgpu_usermode_queue *queue =
-		container_of(kref, struct amdgpu_usermode_queue, refcount);
+		container_of(work, struct amdgpu_usermode_queue, destroy_work);
 	struct amdgpu_userq_mgr *uq_mgr = queue->userq_mgr;
 
 	r = amdgpu_userq_destroy(uq_mgr, queue);
@@ -610,6 +610,14 @@ static void amdgpu_userq_kref_destroy(struct kref *kref)
 	amdgpu_userq_mgr_dec_refs(uq_mgr);
 }
 
+static void amdgpu_userq_kref_release(struct kref *kref)
+{
+	struct amdgpu_usermode_queue *queue =
+		container_of(kref, struct amdgpu_usermode_queue, refcount);
+
+	WARN_ON_ONCE(!queue_work(system_unbound_wq, &queue->destroy_work));
+}
+
 struct amdgpu_usermode_queue *amdgpu_userq_get(struct amdgpu_userq_mgr *uq_mgr, u32 qid)
 {
 	struct amdgpu_usermode_queue *queue;
@@ -656,7 +664,7 @@ amdgpu_lookup_queue_by_doorbell(struct xarray *xa, u32 doorbell)
 void amdgpu_userq_put(struct amdgpu_usermode_queue *queue)
 {
 	if (queue)
-		kref_put(&queue->refcount, amdgpu_userq_kref_destroy);
+		kref_put(&queue->refcount, amdgpu_userq_kref_release);
 }
 
 static int amdgpu_userq_priority_permit(struct drm_file *filp,
@@ -724,6 +732,7 @@ amdgpu_userq_create(struct drm_file *filp, union drm_amdgpu_userq *args)
 	amdgpu_userq_mgr_inc_refs(uq_mgr);
 	INIT_DELAYED_WORK(&queue->hang_detect_work,
 			  amdgpu_userq_hang_detect_work);
+	INIT_WORK(&queue->destroy_work, amdgpu_userq_destroy_worker);
 
 	r = amdgpu_userq_fence_driver_alloc(adev, &queue->fence_drv);
 	if (r)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.h
index a13d8d4dd5c7..ecc450be7eb2 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.h
@@ -87,6 +87,13 @@ struct amdgpu_usermode_queue {
 	 * Delayed work which runs when userq_fences time out.
 	 */
 	struct delayed_work	hang_detect_work;
+
+	/**
+	 * @destroy_work:
+	 *
+	 * Work struct used to destroy the queue when kref == 0
+	 */
+	struct work_struct	destroy_work;
 	struct kref		refcount;
 
 	union {
-- 
2.53.0