[PATCH v2] drm/amdgpu: Fix eviction fence worker race during fd close

[Jesse.Zhang]

The current cleanup order during file descriptor close can lead to
a race condition where the eviction fence worker attempts to access
a destroyed mutex from the user queue manager:

[  517.294055] DEBUG_LOCKS_WARN_ON(lock->magic != lock)
[  517.294060] WARNING: CPU: 8 PID: 2030 at kernel/locking/mutex.c:564
[  517.294094] Workqueue: events amdgpu_eviction_fence_suspend_worker [amdgpu]

The issue occurs because:
1. We destroy the user queue manager (including its mutex) first
2. Then try to destroy eviction fences which may have pending work
3. The eviction fence worker may try to access the already-destroyed mutex

Fix this by reordering the cleanup to:
1. First mark the fd as closing and destroy eviction fences,
   which flushes any pending work
2. Then safely destroy the user queue manager after we're certain
   no more fence work will be executed

v2: remove the copy in amdgpu_driver_postclose_kms() (Christian)

Signed-off-by: Jesse Zhang <Jesse.Zhang at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 2 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c | 5 -----
 2 files changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
index 4ddd08ce8885..4db92e0a60da 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
@@ -2913,8 +2913,8 @@ static int amdgpu_drm_release(struct inode *inode, struct file *filp)
 
 	if (fpriv) {
 		fpriv->evf_mgr.fd_closing = true;
-		amdgpu_userq_mgr_fini(&fpriv->userq_mgr);
 		amdgpu_eviction_fence_destroy(&fpriv->evf_mgr);
+		amdgpu_userq_mgr_fini(&fpriv->userq_mgr);
 	}
 
 	return drm_release(inode, filp);
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
index 9fbb04aee97b..d2ce7d86dbc8 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
@@ -1502,11 +1502,6 @@ void amdgpu_driver_postclose_kms(struct drm_device *dev,
 		amdgpu_bo_unreserve(pd);
 	}
 
-	if (!fpriv->evf_mgr.fd_closing) {
-		fpriv->evf_mgr.fd_closing = true;
-		amdgpu_userq_mgr_fini(&fpriv->userq_mgr);
-		amdgpu_eviction_fence_destroy(&fpriv->evf_mgr);
-	}
 	amdgpu_ctx_mgr_fini(&fpriv->ctx_mgr);
 	amdgpu_vm_fini(adev, &fpriv->vm);
 
-- 
2.49.0