[PATCH 5/5] drm/amdkfd: svm deferred work pin mm

[Philip Yang]

Make sure mm does not remove when prange deferred work insert mmu range
notifier, to avoid WARNING:

WARNING: CPU: 6 PID: 1787 at mm/mmu_notifier.c:932 
__mmu_interval_notifier_insert+0xdd/0xf0
Workqueue: events svm_range_deferred_list_work [amdgpu]
RIP: 0010:__mmu_interval_notifier_insert+0xdd/0xf0
Call Trace:
  svm_range_deferred_list_work+0x156/0x320 [amdgpu]
  process_one_work+0x29f/0x5e0
  worker_thread+0x39/0x3e0

Signed-off-by: Philip Yang <philip.y...@amd.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c 
b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index 2083a10b35c2..fddf0a93d6f1 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -1992,6 +1992,13 @@ static void svm_range_deferred_list_work(struct 
work_struct *work)
                         prange->start, prange->last, prange->work_item.op);
 
                mm = prange->work_item.mm;
+               if (!mmget_not_zero(mm)) {
+                       pr_debug("skip range %p as mm is gone\n", prange);
+                       spin_lock(&svms->deferred_list_lock);
+                       list_del_init(&prange->deferred_list);
+                       continue;
+               }
+
 retry:
                mmap_write_lock(mm);
                mutex_lock(&svms->lock);
@@ -2032,6 +2039,7 @@ static void svm_range_deferred_list_work(struct 
work_struct *work)
                svm_range_handle_list_op(svms, prange);
                mutex_unlock(&svms->lock);
                mmap_write_unlock(mm);
+               mmput(mm);
 
                spin_lock(&svms->deferred_list_lock);
        }
-- 
2.17.1