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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"><span style="font-size:11.0pt;font-family:"Arial",sans-serif">Hi Philip,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Arial",sans-serif"> Upon further consideration, removing amdgpu_amdkfd_unreserve_mem_limit is challenging because it is paired with amdgpu_amdkfd_reserve_mem_limit in svm_migrate_ram_to_vram.
However, this pairing does introduce issues, as it prevents amdgpu_amdkfd_reserve_mem_limit from accurately detecting out-of-memory conditions. Ideally, amdgpu_amdkfd_unreserve_mem_limit should be tied to the actual freeing of memory. Furthermore, since ttm_bo_delayed_delete delays
the call to amdgpu_vram_mgr_del, there remains a possibility that amdgpu_amdkfd_reserve_mem_limit reports sufficient memory, while a subsequent call to amdgpu_vram_mgr_new fails. For these reasons, I believe this patch is still necessary.<o:p></o:p></span></p>
<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"><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"> amd-gfx <amd-gfx-bounces@lists.freedesktop.org>
<b>On Behalf Of </b>Deng, Emily<br>
<b>Sent:</b> Tuesday, February 11, 2025 6:56 PM<br>
<b>To:</b> Yang, Philip <Philip.Yang@amd.com>; Chen, Xiaogang <Xiaogang.Chen@amd.com>; amd-gfx@lists.freedesktop.org<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>
<p style="margin:5.0pt"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif;color:blue">[AMD Official Use Only - AMD Internal Distribution Only]<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p style="margin:5.0pt"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif;color:blue">[AMD Official Use Only - AMD Internal Distribution Only]<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></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 class="MsoNormal"><span style="font-size:11.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
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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"> Yang, Philip <<a href="mailto:Philip.Yang@amd.com">Philip.Yang@amd.com</a>>
<br>
<b>Sent:</b> Tuesday, February 11, 2025 6:54 AM<br>
<b>To:</b> Deng, Emily <<a href="mailto:Emily.Deng@amd.com">Emily.Deng@amd.com</a>>; Chen, Xiaogang <<a href="mailto:Xiaogang.Chen@amd.com">Xiaogang.Chen@amd.com</a>>;
<a 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>
<p><o:p> </o:p></p>
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<p class="MsoNormal">On 2025-02-10 02:51, Deng, Emily wrote:<o:p></o:p></p>
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<p style="margin:5.0pt"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif;color:blue">[AMD Official Use Only - AMD Internal Distribution Only]<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p style="margin:5.0pt"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif;color:blue">[AMD Official Use Only - AMD Internal Distribution Only]<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Arial",sans-serif"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Arial",sans-serif"> </span><o:p></o:p></p>
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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 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 href="mailto:Emily.Deng@amd.com"><Emily.Deng@amd.com></a>;
<a 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</span><o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
<p> <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"><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">amd-gfx@lists.freedesktop.org</a><o:p></o:p></pre>
<pre>Cc: Deng, Emily <a href="mailto:Emily.Deng@amd.com"><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.<o:p></o:p></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.<o:p></o:p></p>
<p>Regards,<o:p></o:p></p>
<p>Philip<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Arial",sans-serif">Hi Philip,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Arial",sans-serif"> You're correct. Upon further investigation, the issue arises from the additional call to amdgpu_amdkfd_unreserve_mem_limit in svm_migrate_ram_to_vram, which prevents amdgpu_amdkfd_reserve_mem_limit from
detecting the out-of-memory condition. I will submit another patch to remove the amdgpu_amdkfd_unreserve_mem_limit call in svm_migrate_ram_to_vram.</span><o:p></o:p></p>
<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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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Arial",sans-serif"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;mso-ligatures:standardcontextual">Emily Deng</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;mso-ligatures:standardcontextual">Best Wishes</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Arial",sans-serif"> </span><o:p></o:p></p>
<p><span style="font-size:11.0pt;font-family:"Arial",sans-serif"> </span><o:p></o:p></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"><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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