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<div class="moz-cite-prefix">On 2/7/2025 9:02 PM, Deng, Emily wrote:<br>
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<pre wrap="" class="moz-quote-pre">[AMD Official Use Only - AMD Internal Distribution Only]
[AMD Official Use Only - AMD Internal Distribution Only]
Ping.......
Emily Deng
Best Wishes
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<pre wrap="" class="moz-quote-pre">-----Original Message-----
From: Emily Deng <a class="moz-txt-link-rfc2396E" href="mailto:Emily.Deng@amd.com"><Emily.Deng@amd.com></a>
Sent: Friday, February 7, 2025 6:28 PM
To: <a class="moz-txt-link-abbreviated" href="mailto:amd-gfx@lists.freedesktop.org">amd-gfx@lists.freedesktop.org</a>
Cc: Deng, Emily <a class="moz-txt-link-rfc2396E" href="mailto:Emily.Deng@amd.com"><Emily.Deng@amd.com></a>
Subject: [PATCH] drm/amdkfd: Fix the deadlock in svm_range_restore_work
It will hit deadlock in svm_range_restore_work ramdonly.
Detail as below:
1.svm_range_restore_work
->svm_range_list_lock_and_flush_work
->mmap_write_lock
2.svm_range_restore_work
->svm_range_validate_and_map
->amdgpu_vm_update_range
->amdgpu_vm_ptes_update
->amdgpu_vm_pt_alloc
->svm_range_evict_svm_bo_worker</pre>
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<p><span style="white-space: pre-wrap">svm_range_evict_svm_bo_worker is a function running by a kernel task from default system_wq. It is not the task that runs </span><span style="white-space: pre-wrap">svm_range_restore_work which is from system_freezable_wq. The second task may need wait the first task to release </span><span style="white-space: pre-wrap">mmap_write_lock, but there is no cycle lock dependency.</span></p>
<p><span style="white-space: pre-wrap">Can you explain more how deadlock happened? If a deadlock exists between two tasks there are should be at least two locks used by both tasks.</span></p>
<p><span style="white-space: pre-wrap">Regards</span></p>
<p><span style="white-space: pre-wrap">Xiaogang
</span></p>
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->mmap_read_lock(deadlock here, because already get mmap_write_lock)
How to fix?
Downgrade the write lock to read lock.
Signed-off-by: Emily Deng <a class="moz-txt-link-rfc2396E" href="mailto:Emily.Deng@amd.com"><Emily.Deng@amd.com></a>
---
drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index bd3e20d981e0..c907e2de3dde 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -1841,6 +1841,7 @@ static void svm_range_restore_work(struct work_struct
*work)
mutex_lock(&process_info->lock);
svm_range_list_lock_and_flush_work(svms, mm);
mutex_lock(&svms->lock);
+ mmap_write_downgrade(mm);
evicted_ranges = atomic_read(&svms->evicted_ranges);
@@ -1890,7 +1891,7 @@ static void svm_range_restore_work(struct work_struct
*work)
out_reschedule:
mutex_unlock(&svms->lock);
- mmap_write_unlock(mm);
+ mmap_read_unlock(mm);
mutex_unlock(&process_info->lock);
/* If validation failed, reschedule another attempt */
--
2.34.1
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