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<div class="moz-cite-prefix">On 2025-02-10 02:51, Deng, Emily wrote:<br>
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<p style="font-family:Calibri;font-size:10pt;color:#0000FF;margin:5pt;font-style:normal;font-weight:normal;text-decoration:none;" align="Left">
[AMD Official Use Only - AMD Internal Distribution Only]<br>
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<p style="font-family:Calibri;font-size:10pt;color:#0000FF;margin:5pt;font-style:normal;font-weight:normal;text-decoration:none;" align="Left">
[AMD Official Use Only - AMD Internal Distribution Only]<br>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">
Chen, Xiaogang <a class="moz-txt-link-rfc2396E" href="mailto:Xiaogang.Chen@amd.com"><Xiaogang.Chen@amd.com></a>
<br>
<b>Sent:</b> Monday, February 10, 2025 10:18 AM<br>
<b>To:</b> Deng, Emily <a class="moz-txt-link-rfc2396E" href="mailto:Emily.Deng@amd.com"><Emily.Deng@amd.com></a>;
<a class="moz-txt-link-abbreviated" href="mailto:amd-gfx@lists.freedesktop.org">amd-gfx@lists.freedesktop.org</a><br>
<b>Subject:</b> Re: [PATCH] drm/amdkfd: Fix the
deadlock in svm_range_restore_work<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On 2/7/2025 9:02 PM, Deng, Emily
wrote:<o:p></o:p></p>
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<pre>[AMD Official Use Only - AMD Internal Distribution Only]<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>[AMD Official Use Only - AMD Internal Distribution Only]<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>Ping.......<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>Emily Deng<o:p></o:p></pre>
<pre>Best Wishes<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre><o:p> </o:p></pre>
<pre><o:p> </o:p></pre>
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<pre>-----Original Message-----<o:p></o:p></pre>
<pre>From: Emily Deng <a href="mailto:Emily.Deng@amd.com" moz-do-not-send="true"><Emily.Deng@amd.com></a><o:p></o:p></pre>
<pre>Sent: Friday, February 7, 2025 6:28 PM<o:p></o:p></pre>
<pre>To: <a href="mailto:amd-gfx@lists.freedesktop.org" moz-do-not-send="true" class="moz-txt-link-freetext">amd-gfx@lists.freedesktop.org</a><o:p></o:p></pre>
<pre>Cc: Deng, Emily <a href="mailto:Emily.Deng@amd.com" moz-do-not-send="true"><Emily.Deng@amd.com></a><o:p></o:p></pre>
<pre>Subject: [PATCH] drm/amdkfd: Fix the deadlock in svm_range_restore_work<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>It will hit deadlock in svm_range_restore_work ramdonly.<o:p></o:p></pre>
<pre>Detail as below:<o:p></o:p></pre>
<pre>1.svm_range_restore_work<o:p></o:p></pre>
<pre> ->svm_range_list_lock_and_flush_work<o:p></o:p></pre>
<pre> ->mmap_write_lock<o:p></o:p></pre>
<pre>2.svm_range_restore_work<o:p></o:p></pre>
<pre> ->svm_range_validate_and_map<o:p></o:p></pre>
<pre> ->amdgpu_vm_update_range<o:p></o:p></pre>
<pre> ->amdgpu_vm_ptes_update<o:p></o:p></pre>
<pre> ->amdgpu_vm_pt_alloc<o:p></o:p></pre>
<pre> ->svm_range_evict_svm_bo_worker<o:p></o:p></pre>
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<p>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 svm_range_restore_work which is from
system_freezable_wq. The second task may need wait the
first task to release mmap_write_lock, but there is no
cycle lock dependency.<o:p></o:p></p>
<p>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.<o:p></o:p></p>
<p>Regards<o:p></o:p></p>
<p style="margin-left:11.0pt">Xiaogang <o:p></o:p></p>
<p style="margin-left:5.5pt">In Step 2, during
the amdgpu_vm_pt_alloc process, the system encounters
insufficient memory and triggers an eviction. This
initiates the svm_range_evict_svm_bo_worker task, and
waits for the eviction_fence to be signaled. However,
the svm_range_evict_svm_bo_worker cannot acquire
the mmap_read_lock(mm), preventing it from signaling
the eviction_fence. As a
result, amdgpu_vm_pt_alloc remains incomplete and cannot
release the mmap_write_lock(mm).
<o:p></o:p></p>
<p style="margin-left:5.5pt">Which means
the svm_range_restore_work task holds
the mmap_write_lock(mm) and is stuck waiting for
the eviction_fence to be signaled
by svm_range_evict_svm_bo_worker.
However, svm_range_evict_svm_bo_worker is itself
blocked, unable to acquire the mmap_read_lock(mm). This
creates a deadlock.</p>
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<p>The deadlock situation should not happen as
svm_range_restore_work is only used for xnack off case, there is
no VRAM over commitment with KFD amdgpu_amdkfd_reserve_mem_limit.
We reserved VRAM ESTIMATE_PT_SIZE for page table allocation to
prevent this situation.</p>
<p>Regards,</p>
<p>Philip<br>
</p>
<blockquote type="cite" cite="mid:PH0PR12MB54174DCAA0C2AF44C320C1098FF22@PH0PR12MB5417.namprd12.prod.outlook.com">
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;mso-ligatures:standardcontextual">Emily
Deng<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;mso-ligatures:standardcontextual">Best
Wishes<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p><span style="font-size:11.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
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<pre> ->mmap_read_lock(deadlock here, because already get mmap_write_lock)<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>How to fix?<o:p></o:p></pre>
<pre>Downgrade the write lock to read lock.<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>Signed-off-by: Emily Deng <a href="mailto:Emily.Deng@amd.com" moz-do-not-send="true"><Emily.Deng@amd.com></a><o:p></o:p></pre>
<pre>---<o:p></o:p></pre>
<pre>drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 3 ++-<o:p></o:p></pre>
<pre>1 file changed, 2 insertions(+), 1 deletion(-)<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c<o:p></o:p></pre>
<pre>b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c<o:p></o:p></pre>
<pre>index bd3e20d981e0..c907e2de3dde 100644<o:p></o:p></pre>
<pre>--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c<o:p></o:p></pre>
<pre>+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c<o:p></o:p></pre>
<pre>@@ -1841,6 +1841,7 @@ static void svm_range_restore_work(struct work_struct<o:p></o:p></pre>
<pre>*work)<o:p></o:p></pre>
<pre> mutex_lock(&process_info->lock);<o:p></o:p></pre>
<pre> svm_range_list_lock_and_flush_work(svms, mm);<o:p></o:p></pre>
<pre> mutex_lock(&svms->lock);<o:p></o:p></pre>
<pre>+ mmap_write_downgrade(mm);<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre> evicted_ranges = atomic_read(&svms->evicted_ranges);<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>@@ -1890,7 +1891,7 @@ static void svm_range_restore_work(struct work_struct<o:p></o:p></pre>
<pre>*work)<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>out_reschedule:<o:p></o:p></pre>
<pre> mutex_unlock(&svms->lock);<o:p></o:p></pre>
<pre>- mmap_write_unlock(mm);<o:p></o:p></pre>
<pre>+ mmap_read_unlock(mm);<o:p></o:p></pre>
<pre> mutex_unlock(&process_info->lock);<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre> /* If validation failed, reschedule another attempt */<o:p></o:p></pre>
<pre>--<o:p></o:p></pre>
<pre>2.34.1<o:p></o:p></pre>
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