Am 12.12.23 um 00:43 schrieb Felix Kuehling:
On 2023-12-11 05:38, Christian König wrote:
Am 09.12.23 um 00:01 schrieb James Zhu:
Needn't do schedule for each hmm_range_fault, and use cond_resched
to replace schedule.
cond_resched() is usually NAKed upstream since it is a NO-OP in most
situations.
That's weird, because https://docs.kernel.org/RCU/stallwarn.html
specifically recommends it to resolve RCU stall warnings. I previously
told James to use that instead of schedule().
I haven't followed the full discussion and rational about that either,
could be that the documentation is outdated.
The latest RFC to remove cond_resched() and explaining the background
can be found here: https://lwn.net/Articles/950581/
Regards,
Christian.
Regards,
Felix
IIRC there was even a patch set to completely remove it.
Christian.
Signed-off-by: James Zhu <James.Zhu@xxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.c
index b24eb5821fd1..c77c4eceea46 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.c
@@ -199,6 +199,7 @@ int amdgpu_hmm_range_get_pages(struct
mmu_interval_notifier *notifier,
hmm_range->notifier_seq = mmu_interval_read_begin(notifier);
r = hmm_range_fault(hmm_range);
if (unlikely(r)) {
+ cond_resched();
/*
* FIXME: This timeout should encompass the retry from
* mmu_interval_read_retry() as well.
@@ -212,7 +213,6 @@ int amdgpu_hmm_range_get_pages(struct
mmu_interval_notifier *notifier,
break;
hmm_range->hmm_pfns += MAX_WALK_BYTE >> PAGE_SHIFT;
hmm_range->start = hmm_range->end;
- schedule();
} while (hmm_range->end < end);
hmm_range->start = start;
