On 2023-09-20 2:17, Xiaogang.Chen wrote:
From: Xiaogang Chen <xiaogang.chen@xxxxxxx>
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.
I agree with this part.
2: During waiting svm_bo of prange got released in a while loop should schedule
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.
We had a similar discussion a few weeks back for another soft lock and I
pointed to cond_reschedule, which seems to be the preferred way to
avoid soft locks in the kernel. Does cond_reschedule work for this case?
Regards,
Felix
Signed-off-by: Xiaogang.Chen <Xiaogang.Chen@xxxxxxx>
---
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..1074a4aedf57 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)
+ schedule();
return false;
}
