drm/imagination: Fix double call to drm_sched_entity_fini()

Call sequence of double call:
pvr_context_destroy
  pvr_context_kill_queues
    pvr_queue_kill
      drm_sched_entity_destroy
        drm_sched_entity_fini // here
  pvr_context_put
    kref_put(..., pvr_context_release)
      pvr_context_destroy_queues
        pvr_queue_destroy
          drm_sched_entity_fini // here

Call to drm_sched_entity_destroy() from pvr_context_kill_queues() calls
drm_sched_entity_flush() + drm_sched_entity_fini().
drm_sched_entity_flush() ensures all pending jobs are completed and
drm_sched_entity_fini() ensures no further submission is allowed as
per expectation from pvr_context_kill_queues(). Double call to
drm_sched_entity_fini() is misuse of the API so keep call only in
pvr_context_create() failure path.

Stack trace for issue with addition of refcounting for DRM entity
stats in commit fd177135f0e6 ("drm/sched: Account entity GPU time"):

[  789.490527] ------------[ cut here ]------------
[  789.490559] refcount_t: underflow; use-after-free.
[  789.490657] WARNING: lib/refcount.c:28 at refcount_warn_saturate+0xf4/0x144, CPU#0: kworker/u16:1/440
[  789.490695] Modules linked in: powervr drm_gpuvm drm_exec gpu_sched drm_shmem_helper xhci_plat_hcd xhci_hcd dwc3 usbcore usb_common snd_soc_simple_card snd_soc_simple_card_utils sa2ul sha512 sha256 dwc3_am62 sha1 authenc rti_wdt libsha512 at24 sch_fq_codel fuse dm_mod ipv6
[  789.490798] CPU: 0 UID: 0 PID: 440 Comm: kworker/u16:1 Not tainted 7.0.0-rc7-02049-g5e2c0700091b #22 PREEMPT
[  789.490809] Hardware name: Texas Instruments AM625 SK (DT)
[  789.490815] Workqueue: powervr-sched pvr_queue_fence_release_work [powervr]
[  789.490868] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[  789.490876] pc : refcount_warn_saturate+0xf4/0x144
[  789.490884] lr : refcount_warn_saturate+0xf4/0x144
[  789.490892] sp : ffff8000822cbcc0
[  789.490895] x29: ffff8000822cbcc0 x28: 0000000000000000 x27: 0000000000000000
[  789.490909] x26: 0000000000000000 x25: ffff800081b1e338 x24: ffff000004541405
[  789.490922] x23: ffff000004bea950 x22: ffff00000042e400 x21: ffff000007123e30
[  789.490935] x20: ffff000007123000 x19: ffff000007a80d50 x18: fffffffffffe7768
[  789.490948] x17: 74736574202c6e6f x16: 697461746e656d65 x15: ffff800081b269f0
[  789.490962] x14: 0000000000000030 x13: ffff800081b26a70 x12: 0000000000000211
[  789.490975] x11: 00000000000000c0 x10: 0000000000000b50 x9 : ffff8000822cbb30
[  789.490988] x8 : ffff0000014e7bb0 x7 : ffff00007725e780 x6 : 0000000372a05f49
[  789.491001] x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000010
[  789.491013] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0000014e7000
[  789.491027] Call trace:
[  789.491032]  refcount_warn_saturate+0xf4/0x144 (P)
[  789.491043]  drm_sched_entity_fini+0x164/0x18c [gpu_sched]
[  789.491081]  pvr_queue_destroy+0x64/0x134 [powervr]
[  789.491110]  pvr_context_destroy_queues+0x34/0x64 [powervr]
[  789.491138]  pvr_context_release+0x70/0xac [powervr]
[  789.491166]  pvr_context_put.part.0+0x5c/0x7c [powervr]
[  789.491193]  pvr_context_put+0x14/0x24 [powervr]
[  789.491221]  pvr_queue_fence_release_work+0x20/0x38 [powervr]
[  789.491249]  process_one_work+0x160/0x4c4
[  789.491264]  worker_thread+0x188/0x310
[  789.491276]  kthread+0x130/0x13c
[  789.491287]  ret_from_fork+0x10/0x20
[  789.491300] ---[ end trace 0000000000000000 ]---

Fixes: eaf01ee5ba28 ("drm/imagination: Implement job submission and scheduling")
Cc: stable@vger.kernel.org
Signed-off-by: Brajesh Gupta <brajesh.gupta@imgtec.com>
Reviewed-by: Alessio Belle <alessio.belle@imgtec.com>
Link: https://patch.msgid.link/20260630-b4-sched_fix-v7-1-71aa39c62627@imgtec.com
Signed-off-by: Alessio Belle <alessio.belle@imgtec.com>

3 files changed, 15 insertions, 11 deletions

diff --git a/drivers/gpu/drm/imagination/pvr_context.c b/drivers/gpu/drm/imagination/pvr_context.c
index eba4694400b5..52e16c1e7af0 100644
--- a/drivers/gpu/drm/imagination/pvr_context.c
+++ b/drivers/gpu/drm/imagination/pvr_context.c
@@ -161,22 +161,24 @@ ctx_fw_data_init(void *cpu_ptr, void *priv)
 /**
  * pvr_context_destroy_queues() - Destroy all queues attached to a context.
  * @ctx: Context to destroy queues on.
+ * @cleanup_queue_entity: Whether to cleanup the queue entity e.g. context
+ * creation failure path.
  *
  * Should be called when the last reference to a context object is dropped.
  * It releases all resources attached to the queues bound to this context.
  */
-static void pvr_context_destroy_queues(struct pvr_context *ctx)
+static void pvr_context_destroy_queues(struct pvr_context *ctx, bool cleanup_queue_entity)
 {
 	switch (ctx->type) {
 	case DRM_PVR_CTX_TYPE_RENDER:
-		pvr_queue_destroy(ctx->queues.fragment);
-		pvr_queue_destroy(ctx->queues.geometry);
+		pvr_queue_destroy(ctx->queues.fragment, cleanup_queue_entity);
+		pvr_queue_destroy(ctx->queues.geometry, cleanup_queue_entity);
 		break;
 	case DRM_PVR_CTX_TYPE_COMPUTE:
-		pvr_queue_destroy(ctx->queues.compute);
+		pvr_queue_destroy(ctx->queues.compute, cleanup_queue_entity);
 		break;
 	case DRM_PVR_CTX_TYPE_TRANSFER_FRAG:
-		pvr_queue_destroy(ctx->queues.transfer);
+		pvr_queue_destroy(ctx->queues.transfer, cleanup_queue_entity);
 		break;
 	}
 }
@@ -240,7 +242,7 @@ static int pvr_context_create_queues(struct pvr_context *ctx,
 	return -EINVAL;
 
 err_destroy_queues:
-	pvr_context_destroy_queues(ctx);
+	pvr_context_destroy_queues(ctx, true);
 	return err;
 }
 
@@ -349,7 +351,7 @@ err_destroy_fw_obj:
 	pvr_fw_object_destroy(ctx->fw_obj);
 
 err_destroy_queues:
-	pvr_context_destroy_queues(ctx);
+	pvr_context_destroy_queues(ctx, true);
 
 err_free_ctx_id:
 	/*
@@ -384,7 +386,7 @@ pvr_context_release(struct kref *ref_count)
 	spin_unlock(&pvr_dev->ctx_list_lock);
 
 	xa_erase(&pvr_dev->ctx_ids, ctx->ctx_id);
-	pvr_context_destroy_queues(ctx);
+	pvr_context_destroy_queues(ctx, false);
 	pvr_fw_object_destroy(ctx->fw_obj);
 	kfree(ctx->data);
 	pvr_vm_context_put(ctx->vm_ctx);
diff --git a/drivers/gpu/drm/imagination/pvr_queue.c b/drivers/gpu/drm/imagination/pvr_queue.c
index 7ed60e1c1a86..941c017399fc 100644
--- a/drivers/gpu/drm/imagination/pvr_queue.c
+++ b/drivers/gpu/drm/imagination/pvr_queue.c
@@ -1439,11 +1439,12 @@ void pvr_queue_kill(struct pvr_queue *queue)
 /**
  * pvr_queue_destroy() - Destroy a queue.
  * @queue: The queue to destroy.
+ * @cleanup_queue_entity: Whether to cleanup the queue entity.
  *
  * Cleanup the queue and free the resources attached to it. Should be
  * called from the context release function.
  */
-void pvr_queue_destroy(struct pvr_queue *queue)
+void pvr_queue_destroy(struct pvr_queue *queue, bool cleanup_queue_entity)
 {
 	if (!queue)
 		return;
@@ -1453,7 +1454,8 @@ void pvr_queue_destroy(struct pvr_queue *queue)
 	mutex_unlock(&queue->ctx->pvr_dev->queues.lock);
 
 	drm_sched_fini(&queue->scheduler);
-	drm_sched_entity_fini(&queue->entity);
+	if (cleanup_queue_entity)
+		drm_sched_entity_fini(&queue->entity);
 
 	if (WARN_ON(queue->last_queued_job_scheduled_fence))
 		dma_fence_put(queue->last_queued_job_scheduled_fence);
diff --git a/drivers/gpu/drm/imagination/pvr_queue.h b/drivers/gpu/drm/imagination/pvr_queue.h
index 4aa72665ce25..149cc6d124bf 100644
--- a/drivers/gpu/drm/imagination/pvr_queue.h
+++ b/drivers/gpu/drm/imagination/pvr_queue.h
@@ -158,7 +158,7 @@ struct pvr_queue *pvr_queue_create(struct pvr_context *ctx,
 
 void pvr_queue_kill(struct pvr_queue *queue);
 
-void pvr_queue_destroy(struct pvr_queue *queue);
+void pvr_queue_destroy(struct pvr_queue *queue, bool cleanup_queue_entity);
 
 void pvr_queue_process(struct pvr_queue *queue);