From: Xiaogang Chen <xiaogang.c...@amd.com>

This patch fixes:
1: ref number of prange's svm_bo got decreased by an async call from hmm. When
wait svm_bo of prange got released we shoul also wait prang->svm_bo become NULL,
otherwise prange->svm_bo may be set to null after allocate new vram buffer.

2: During waiting svm_bo of prange got released in a while loop should 
reschedule
current task to give other tasks oppotunity to run, specially the the workque
task that handles svm_bo ref release, otherwise we may enter to softlock.

Signed-off-by: Xiaogang.Chen <xiaogang.c...@amd.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c 
b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index bed0f8bf83c7..164cd77af62d 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -502,11 +502,11 @@ svm_range_validate_svm_bo(struct kfd_node *node, struct 
svm_range *prange)
 
        /* We need a new svm_bo. Spin-loop to wait for concurrent
         * svm_range_bo_release to finish removing this range from
-        * its range list. After this, it is safe to reuse the
-        * svm_bo pointer and svm_bo_list head.
+        * its range list and set prange->svm_bo to null. After this,
+        * it is safe to reuse the svm_bo pointer and svm_bo_list head.
         */
-       while (!list_empty_careful(&prange->svm_bo_list))
-               ;
+       while (!list_empty_careful(&prange->svm_bo_list) || prange->svm_bo)
+               cond_resched();
 
        return false;
 }
-- 
2.25.1

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