common/recipes-kernel/linux/linux-yocto-4.14.71/4148-drm-amdkfd-Take-reference-to-gtt-usertask.patch


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From 2f624615743214a059c25bde1525daac702c88d0 Mon Sep 17 00:00:00 2001
From: Felix Kuehling <Felix.Kuehling@amd.com>
Date: Mon, 19 Mar 2018 16:01:16 -0400
Subject: [PATCH 4148/5725] drm/amdkfd: Take reference to gtt->usertask

Theoretically the task struct can be destroyed before the BO. Use
the task_struct's reference count to prevent that.

Change-Id: I20f0c42c8f521347bc93987d0703db1f07696000
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Kalyan Alle <kalyan.alle@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 71a5c67..6c81f2d 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1024,6 +1024,9 @@ static void amdgpu_ttm_backend_destroy(struct ttm_tt *ttm)
 {
 	struct amdgpu_ttm_tt *gtt = (void *)ttm;
 	
+	if (gtt->usertask)
+		put_task_struct(gtt->usertask);
+
 	ttm_dma_tt_fini(&gtt->ttm);
 	kfree(gtt);
 }
@@ -1112,8 +1115,13 @@ int amdgpu_ttm_tt_set_userptr(struct ttm_tt *ttm, uint64_t addr,
 		return -EINVAL;
 
 	gtt->userptr = addr;
-	gtt->usertask = current->group_leader;
 	gtt->userflags = flags;
+
+	if (gtt->usertask)
+		put_task_struct(gtt->usertask);
+	gtt->usertask = current->group_leader;
+	get_task_struct(gtt->usertask);
+
 	spin_lock_init(&gtt->guptasklock);
 	INIT_LIST_HEAD(&gtt->guptasks);
 	atomic_set(&gtt->mmu_invalidations, 0);
-- 
2.7.4