Change the PerfMap crst into an UNSAFE_ANYMODE crst by davidwrighton · Pull Request #129021 · dotnet/runtime

davidwrighton · 2026-06-04T22:52:28Z

And make sure all logic run under the crst is safe for running in such a place

Also, add logic to handle some simple cases where moving to preemptive is fairly simple. Notably, the VirtualCallStub logic needed these fixes.

…ore ideal for perfmap scenarios

dotnet-policy-service · 2026-06-04T22:53:48Z

Tagging subscribers to this area: @agocke
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

This PR adjusts CoreCLR’s perfmap logging synchronization to avoid GC-mode toggle deadlocks by switching the PerfMap lock to CRST_UNSAFE_ANYMODE, and updates VSD (virtual call stub) stub-generation paths to safely enter preemptive mode where needed when perfmap logging is enabled.

Changes:

Switch PerfMap’s s_csPerfMap to CRST_UNSAFE_ANYMODE to avoid deadlock cycles involving GC-mode toggles during lock acquisition.
Update VirtualCallStubManager stub-generation call sites to temporarily enter preemptive GC mode when perfmap logging is enabled, and reinitialize hash probers after mode transitions.
Add a non-FEATURE_PERFMAP stub PerfMap implementation in perfmap.h so call sites can compile without #ifdef FEATURE_PERFMAP wrappers.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
src/coreclr/vm/virtualcallstub.cpp	Wrap specific stub-generation paths in `GCX_MAYBE_PREEMP` when perfmap is enabled, and reset probers after potential invalidation.
src/coreclr/vm/perfmap.h	Add a stub `PerfMap` class for builds where `FEATURE_PERFMAP` is not defined.
src/coreclr/vm/perfmap.cpp	Initialize the PerfMap lock as `CRST_UNSAFE_ANYMODE` and slightly reduce time holding the lock in `LogPreCompiledMethod`.

Correct LogStubs contract for use on Windows

Copilot

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

davidwrighton · 2026-06-08T21:45:55Z

/backport to release/10.0

github-actions · 2026-06-08T21:46:03Z

Started backporting to release/10.0 (link to workflow run)

github-actions · 2026-06-08T21:47:41Z

@davidwrighton backporting to release/10.0 failed, the patch most likely resulted in conflicts. Please backport manually!

git am output

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patchApplying: Add logic to handle some simple cases where moving to preemptive is more ideal for perfmap scenariosUsing index info to reconstruct a base tree...M	src/coreclr/vm/perfmap.cppM	src/coreclr/vm/perfmap.hM	src/coreclr/vm/virtualcallstub.cppFalling back to patching base and 3-way merge...Auto-merging src/coreclr/vm/perfmap.cppCONFLICT (content): Merge conflict in src/coreclr/vm/perfmap.cppAuto-merging src/coreclr/vm/perfmap.hAuto-merging src/coreclr/vm/virtualcallstub.cpperror: Failed to merge in the changes.hint: Use 'git am --show-current-patch=diff' to see the failed patchhint: When you have resolved this problem, run "git am --continue".hint: If you prefer to skip this patch, run "git am --skip" instead.hint: To restore the original branch and stop patching, run "git am --abort".hint: Disable this message with "git config set advice.mergeConflict false"Patch failed at 0001 Add logic to handle some simple cases where moving to preemptive is more ideal for perfmap scenariosError: The process '/usr/bin/git' failed with exit code 128

Link to workflow output

@leculver

…129142) Backport of #129021 to release/10.0 Fixes#128401 /cc @leculver ## Customer Impact - [x] Customer reported - [ ] Found internally This was reported by customers which found that a service in production would deadlock occasionally when perfmap generation was enabled. ## Regression - [x] Yes - [ ] No This was introduced in #113943 ## Testing Fix was verified through analysis, and the fix also includes an escape hatch environment variable (DOTNET_PerfMapGranularity=4) which will disable the problematic code entirely. ## Risk 1. This fix is only applicable to customers which use perfmaps 2. The fix not only includes code changes which fix the deadlock problem from happening, but also includes a change to add a config switch to avoid the problematic code entirely while keeping the perfmap generation for most scenarios which are interesting to customers. Risks: This fix adjusts a lock so that it will not switch to preemptive mode, and we will run some file I/O while under that lock. This may cause GC latency spikes on some customer workloads. This issue is mitigated by the new switch which can be used to avoid the problem in its entirety at the cost of slightly less accurate profile data for a limited set of scenarios. **IMPORTANT**: If this backport is for a servicing release, please verify that: - For .NET 8 and .NET 9: The PR target branch is `release/X.0-staging`, not `release/X.0`. - For .NET 10+: The PR target branch is `release/X.0` (no `-staging` suffix). ## Package authoring no longer needed in .NET 9 **IMPORTANT**: Starting with .NET 9, you no longer need to edit a NuGet package's csproj to enable building and bump the version. Keep in mind that we still need package authoring in .NET 8 and older versions. --------- Co-authored-by: Jan Kotas <jkotas@microsoft.com>

davidwrighton · 2026-06-04T22:52:28Z

And make sure all logic run under the crst is safe for running in such a place

Also, add logic to handle some simple cases where moving to preemptive is fairly simple. Notably, the VirtualCallStub logic needed these fixes.

…ore ideal for perfmap scenarios

dotnet-policy-service · 2026-06-04T22:53:48Z

Tagging subscribers to this area: @agocke
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

This PR adjusts CoreCLR’s perfmap logging synchronization to avoid GC-mode toggle deadlocks by switching the PerfMap lock to CRST_UNSAFE_ANYMODE, and updates VSD (virtual call stub) stub-generation paths to safely enter preemptive mode where needed when perfmap logging is enabled.

Changes:

Switch PerfMap’s s_csPerfMap to CRST_UNSAFE_ANYMODE to avoid deadlock cycles involving GC-mode toggles during lock acquisition.
Update VirtualCallStubManager stub-generation call sites to temporarily enter preemptive GC mode when perfmap logging is enabled, and reinitialize hash probers after mode transitions.
Add a non-FEATURE_PERFMAP stub PerfMap implementation in perfmap.h so call sites can compile without #ifdef FEATURE_PERFMAP wrappers.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
src/coreclr/vm/virtualcallstub.cpp	Wrap specific stub-generation paths in `GCX_MAYBE_PREEMP` when perfmap is enabled, and reset probers after potential invalidation.
src/coreclr/vm/perfmap.h	Add a stub `PerfMap` class for builds where `FEATURE_PERFMAP` is not defined.
src/coreclr/vm/perfmap.cpp	Initialize the PerfMap lock as `CRST_UNSAFE_ANYMODE` and slightly reduce time holding the lock in `LogPreCompiledMethod`.

Correct LogStubs contract for use on Windows

Copilot

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

davidwrighton · 2026-06-08T21:45:55Z

/backport to release/10.0

github-actions · 2026-06-08T21:46:03Z

Started backporting to release/10.0 (link to workflow run)

github-actions · 2026-06-08T21:47:41Z

@davidwrighton backporting to release/10.0 failed, the patch most likely resulted in conflicts. Please backport manually!

git am output

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patchApplying: Add logic to handle some simple cases where moving to preemptive is more ideal for perfmap scenariosUsing index info to reconstruct a base tree...M	src/coreclr/vm/perfmap.cppM	src/coreclr/vm/perfmap.hM	src/coreclr/vm/virtualcallstub.cppFalling back to patching base and 3-way merge...Auto-merging src/coreclr/vm/perfmap.cppCONFLICT (content): Merge conflict in src/coreclr/vm/perfmap.cppAuto-merging src/coreclr/vm/perfmap.hAuto-merging src/coreclr/vm/virtualcallstub.cpperror: Failed to merge in the changes.hint: Use 'git am --show-current-patch=diff' to see the failed patchhint: When you have resolved this problem, run "git am --continue".hint: If you prefer to skip this patch, run "git am --skip" instead.hint: To restore the original branch and stop patching, run "git am --abort".hint: Disable this message with "git config set advice.mergeConflict false"Patch failed at 0001 Add logic to handle some simple cases where moving to preemptive is more ideal for perfmap scenariosError: The process '/usr/bin/git' failed with exit code 128

Link to workflow output

@leculver

…129142) Backport of #129021 to release/10.0 Fixes#128401 /cc @leculver ## Customer Impact - [x] Customer reported - [ ] Found internally This was reported by customers which found that a service in production would deadlock occasionally when perfmap generation was enabled. ## Regression - [x] Yes - [ ] No This was introduced in #113943 ## Testing Fix was verified through analysis, and the fix also includes an escape hatch environment variable (DOTNET_PerfMapGranularity=4) which will disable the problematic code entirely. ## Risk 1. This fix is only applicable to customers which use perfmaps 2. The fix not only includes code changes which fix the deadlock problem from happening, but also includes a change to add a config switch to avoid the problematic code entirely while keeping the perfmap generation for most scenarios which are interesting to customers. Risks: This fix adjusts a lock so that it will not switch to preemptive mode, and we will run some file I/O while under that lock. This may cause GC latency spikes on some customer workloads. This issue is mitigated by the new switch which can be used to avoid the problem in its entirety at the cost of slightly less accurate profile data for a limited set of scenarios. **IMPORTANT**: If this backport is for a servicing release, please verify that: - For .NET 8 and .NET 9: The PR target branch is `release/X.0-staging`, not `release/X.0`. - For .NET 10+: The PR target branch is `release/X.0` (no `-staging` suffix). ## Package authoring no longer needed in .NET 9 **IMPORTANT**: Starting with .NET 9, you no longer need to edit a NuGet package's csproj to enable building and bump the version. Keep in mind that we still need package authoring in .NET 8 and older versions. --------- Co-authored-by: Jan Kotas <jkotas@microsoft.com>

davidwrighton · 2026-06-04T22:52:28Z

And make sure all logic run under the crst is safe for running in such a place

Also, add logic to handle some simple cases where moving to preemptive is fairly simple. Notably, the VirtualCallStub logic needed these fixes.

…ore ideal for perfmap scenarios

dotnet-policy-service · 2026-06-04T22:53:48Z

Tagging subscribers to this area: @agocke
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

This PR adjusts CoreCLR’s perfmap logging synchronization to avoid GC-mode toggle deadlocks by switching the PerfMap lock to CRST_UNSAFE_ANYMODE, and updates VSD (virtual call stub) stub-generation paths to safely enter preemptive mode where needed when perfmap logging is enabled.

Changes:

Switch PerfMap’s s_csPerfMap to CRST_UNSAFE_ANYMODE to avoid deadlock cycles involving GC-mode toggles during lock acquisition.
Update VirtualCallStubManager stub-generation call sites to temporarily enter preemptive GC mode when perfmap logging is enabled, and reinitialize hash probers after mode transitions.
Add a non-FEATURE_PERFMAP stub PerfMap implementation in perfmap.h so call sites can compile without #ifdef FEATURE_PERFMAP wrappers.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
src/coreclr/vm/virtualcallstub.cpp	Wrap specific stub-generation paths in `GCX_MAYBE_PREEMP` when perfmap is enabled, and reset probers after potential invalidation.
src/coreclr/vm/perfmap.h	Add a stub `PerfMap` class for builds where `FEATURE_PERFMAP` is not defined.
src/coreclr/vm/perfmap.cpp	Initialize the PerfMap lock as `CRST_UNSAFE_ANYMODE` and slightly reduce time holding the lock in `LogPreCompiledMethod`.

Correct LogStubs contract for use on Windows

Copilot

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

davidwrighton · 2026-06-08T21:45:55Z

/backport to release/10.0

github-actions · 2026-06-08T21:46:03Z

Started backporting to release/10.0 (link to workflow run)

github-actions · 2026-06-08T21:47:41Z

@davidwrighton backporting to release/10.0 failed, the patch most likely resulted in conflicts. Please backport manually!

git am output

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patchApplying: Add logic to handle some simple cases where moving to preemptive is more ideal for perfmap scenariosUsing index info to reconstruct a base tree...M	src/coreclr/vm/perfmap.cppM	src/coreclr/vm/perfmap.hM	src/coreclr/vm/virtualcallstub.cppFalling back to patching base and 3-way merge...Auto-merging src/coreclr/vm/perfmap.cppCONFLICT (content): Merge conflict in src/coreclr/vm/perfmap.cppAuto-merging src/coreclr/vm/perfmap.hAuto-merging src/coreclr/vm/virtualcallstub.cpperror: Failed to merge in the changes.hint: Use 'git am --show-current-patch=diff' to see the failed patchhint: When you have resolved this problem, run "git am --continue".hint: If you prefer to skip this patch, run "git am --skip" instead.hint: To restore the original branch and stop patching, run "git am --abort".hint: Disable this message with "git config set advice.mergeConflict false"Patch failed at 0001 Add logic to handle some simple cases where moving to preemptive is more ideal for perfmap scenariosError: The process '/usr/bin/git' failed with exit code 128

Link to workflow output

@leculver

…129142) Backport of #129021 to release/10.0 Fixes#128401 /cc @leculver ## Customer Impact - [x] Customer reported - [ ] Found internally This was reported by customers which found that a service in production would deadlock occasionally when perfmap generation was enabled. ## Regression - [x] Yes - [ ] No This was introduced in #113943 ## Testing Fix was verified through analysis, and the fix also includes an escape hatch environment variable (DOTNET_PerfMapGranularity=4) which will disable the problematic code entirely. ## Risk 1. This fix is only applicable to customers which use perfmaps 2. The fix not only includes code changes which fix the deadlock problem from happening, but also includes a change to add a config switch to avoid the problematic code entirely while keeping the perfmap generation for most scenarios which are interesting to customers. Risks: This fix adjusts a lock so that it will not switch to preemptive mode, and we will run some file I/O while under that lock. This may cause GC latency spikes on some customer workloads. This issue is mitigated by the new switch which can be used to avoid the problem in its entirety at the cost of slightly less accurate profile data for a limited set of scenarios. **IMPORTANT**: If this backport is for a servicing release, please verify that: - For .NET 8 and .NET 9: The PR target branch is `release/X.0-staging`, not `release/X.0`. - For .NET 10+: The PR target branch is `release/X.0` (no `-staging` suffix). ## Package authoring no longer needed in .NET 9 **IMPORTANT**: Starting with .NET 9, you no longer need to edit a NuGet package's csproj to enable building and bump the version. Keep in mind that we still need package authoring in .NET 8 and older versions. --------- Co-authored-by: Jan Kotas <jkotas@microsoft.com>

davidwrighton · 2026-06-04T22:52:28Z

And make sure all logic run under the crst is safe for running in such a place

Also, add logic to handle some simple cases where moving to preemptive is fairly simple. Notably, the VirtualCallStub logic needed these fixes.

…ore ideal for perfmap scenarios

dotnet-policy-service · 2026-06-04T22:53:48Z

Tagging subscribers to this area: @agocke
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

This PR adjusts CoreCLR’s perfmap logging synchronization to avoid GC-mode toggle deadlocks by switching the PerfMap lock to CRST_UNSAFE_ANYMODE, and updates VSD (virtual call stub) stub-generation paths to safely enter preemptive mode where needed when perfmap logging is enabled.

Changes:

Switch PerfMap’s s_csPerfMap to CRST_UNSAFE_ANYMODE to avoid deadlock cycles involving GC-mode toggles during lock acquisition.
Update VirtualCallStubManager stub-generation call sites to temporarily enter preemptive GC mode when perfmap logging is enabled, and reinitialize hash probers after mode transitions.
Add a non-FEATURE_PERFMAP stub PerfMap implementation in perfmap.h so call sites can compile without #ifdef FEATURE_PERFMAP wrappers.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
src/coreclr/vm/virtualcallstub.cpp	Wrap specific stub-generation paths in `GCX_MAYBE_PREEMP` when perfmap is enabled, and reset probers after potential invalidation.
src/coreclr/vm/perfmap.h	Add a stub `PerfMap` class for builds where `FEATURE_PERFMAP` is not defined.
src/coreclr/vm/perfmap.cpp	Initialize the PerfMap lock as `CRST_UNSAFE_ANYMODE` and slightly reduce time holding the lock in `LogPreCompiledMethod`.

Correct LogStubs contract for use on Windows

Copilot

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

davidwrighton · 2026-06-08T21:45:55Z

/backport to release/10.0

github-actions · 2026-06-08T21:46:03Z

Started backporting to release/10.0 (link to workflow run)

github-actions · 2026-06-08T21:47:41Z

@davidwrighton backporting to release/10.0 failed, the patch most likely resulted in conflicts. Please backport manually!

git am output

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patchApplying: Add logic to handle some simple cases where moving to preemptive is more ideal for perfmap scenariosUsing index info to reconstruct a base tree...M	src/coreclr/vm/perfmap.cppM	src/coreclr/vm/perfmap.hM	src/coreclr/vm/virtualcallstub.cppFalling back to patching base and 3-way merge...Auto-merging src/coreclr/vm/perfmap.cppCONFLICT (content): Merge conflict in src/coreclr/vm/perfmap.cppAuto-merging src/coreclr/vm/perfmap.hAuto-merging src/coreclr/vm/virtualcallstub.cpperror: Failed to merge in the changes.hint: Use 'git am --show-current-patch=diff' to see the failed patchhint: When you have resolved this problem, run "git am --continue".hint: If you prefer to skip this patch, run "git am --skip" instead.hint: To restore the original branch and stop patching, run "git am --abort".hint: Disable this message with "git config set advice.mergeConflict false"Patch failed at 0001 Add logic to handle some simple cases where moving to preemptive is more ideal for perfmap scenariosError: The process '/usr/bin/git' failed with exit code 128

Link to workflow output

@leculver

…129142) Backport of #129021 to release/10.0 Fixes#128401 /cc @leculver ## Customer Impact - [x] Customer reported - [ ] Found internally This was reported by customers which found that a service in production would deadlock occasionally when perfmap generation was enabled. ## Regression - [x] Yes - [ ] No This was introduced in #113943 ## Testing Fix was verified through analysis, and the fix also includes an escape hatch environment variable (DOTNET_PerfMapGranularity=4) which will disable the problematic code entirely. ## Risk 1. This fix is only applicable to customers which use perfmaps 2. The fix not only includes code changes which fix the deadlock problem from happening, but also includes a change to add a config switch to avoid the problematic code entirely while keeping the perfmap generation for most scenarios which are interesting to customers. Risks: This fix adjusts a lock so that it will not switch to preemptive mode, and we will run some file I/O while under that lock. This may cause GC latency spikes on some customer workloads. This issue is mitigated by the new switch which can be used to avoid the problem in its entirety at the cost of slightly less accurate profile data for a limited set of scenarios. **IMPORTANT**: If this backport is for a servicing release, please verify that: - For .NET 8 and .NET 9: The PR target branch is `release/X.0-staging`, not `release/X.0`. - For .NET 10+: The PR target branch is `release/X.0` (no `-staging` suffix). ## Package authoring no longer needed in .NET 9 **IMPORTANT**: Starting with .NET 9, you no longer need to edit a NuGet package's csproj to enable building and bump the version. Keep in mind that we still need package authoring in .NET 8 and older versions. --------- Co-authored-by: Jan Kotas <jkotas@microsoft.com>

davidwrighton · 2026-06-04T22:52:28Z

And make sure all logic run under the crst is safe for running in such a place

Also, add logic to handle some simple cases where moving to preemptive is fairly simple. Notably, the VirtualCallStub logic needed these fixes.

…ore ideal for perfmap scenarios

dotnet-policy-service · 2026-06-04T22:53:48Z

Tagging subscribers to this area: @agocke
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

This PR adjusts CoreCLR’s perfmap logging synchronization to avoid GC-mode toggle deadlocks by switching the PerfMap lock to CRST_UNSAFE_ANYMODE, and updates VSD (virtual call stub) stub-generation paths to safely enter preemptive mode where needed when perfmap logging is enabled.

Changes:

Switch PerfMap’s s_csPerfMap to CRST_UNSAFE_ANYMODE to avoid deadlock cycles involving GC-mode toggles during lock acquisition.
Update VirtualCallStubManager stub-generation call sites to temporarily enter preemptive GC mode when perfmap logging is enabled, and reinitialize hash probers after mode transitions.
Add a non-FEATURE_PERFMAP stub PerfMap implementation in perfmap.h so call sites can compile without #ifdef FEATURE_PERFMAP wrappers.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
src/coreclr/vm/virtualcallstub.cpp	Wrap specific stub-generation paths in `GCX_MAYBE_PREEMP` when perfmap is enabled, and reset probers after potential invalidation.
src/coreclr/vm/perfmap.h	Add a stub `PerfMap` class for builds where `FEATURE_PERFMAP` is not defined.
src/coreclr/vm/perfmap.cpp	Initialize the PerfMap lock as `CRST_UNSAFE_ANYMODE` and slightly reduce time holding the lock in `LogPreCompiledMethod`.

Correct LogStubs contract for use on Windows

Copilot

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

davidwrighton · 2026-06-08T21:45:55Z

/backport to release/10.0

github-actions · 2026-06-08T21:46:03Z

Started backporting to release/10.0 (link to workflow run)

github-actions · 2026-06-08T21:47:41Z

@davidwrighton backporting to release/10.0 failed, the patch most likely resulted in conflicts. Please backport manually!

git am output

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patchApplying: Add logic to handle some simple cases where moving to preemptive is more ideal for perfmap scenariosUsing index info to reconstruct a base tree...M	src/coreclr/vm/perfmap.cppM	src/coreclr/vm/perfmap.hM	src/coreclr/vm/virtualcallstub.cppFalling back to patching base and 3-way merge...Auto-merging src/coreclr/vm/perfmap.cppCONFLICT (content): Merge conflict in src/coreclr/vm/perfmap.cppAuto-merging src/coreclr/vm/perfmap.hAuto-merging src/coreclr/vm/virtualcallstub.cpperror: Failed to merge in the changes.hint: Use 'git am --show-current-patch=diff' to see the failed patchhint: When you have resolved this problem, run "git am --continue".hint: If you prefer to skip this patch, run "git am --skip" instead.hint: To restore the original branch and stop patching, run "git am --abort".hint: Disable this message with "git config set advice.mergeConflict false"Patch failed at 0001 Add logic to handle some simple cases where moving to preemptive is more ideal for perfmap scenariosError: The process '/usr/bin/git' failed with exit code 128

Link to workflow output

@leculver

…129142) Backport of #129021 to release/10.0 Fixes#128401 /cc @leculver ## Customer Impact - [x] Customer reported - [ ] Found internally This was reported by customers which found that a service in production would deadlock occasionally when perfmap generation was enabled. ## Regression - [x] Yes - [ ] No This was introduced in #113943 ## Testing Fix was verified through analysis, and the fix also includes an escape hatch environment variable (DOTNET_PerfMapGranularity=4) which will disable the problematic code entirely. ## Risk 1. This fix is only applicable to customers which use perfmaps 2. The fix not only includes code changes which fix the deadlock problem from happening, but also includes a change to add a config switch to avoid the problematic code entirely while keeping the perfmap generation for most scenarios which are interesting to customers. Risks: This fix adjusts a lock so that it will not switch to preemptive mode, and we will run some file I/O while under that lock. This may cause GC latency spikes on some customer workloads. This issue is mitigated by the new switch which can be used to avoid the problem in its entirety at the cost of slightly less accurate profile data for a limited set of scenarios. **IMPORTANT**: If this backport is for a servicing release, please verify that: - For .NET 8 and .NET 9: The PR target branch is `release/X.0-staging`, not `release/X.0`. - For .NET 10+: The PR target branch is `release/X.0` (no `-staging` suffix). ## Package authoring no longer needed in .NET 9 **IMPORTANT**: Starting with .NET 9, you no longer need to edit a NuGet package's csproj to enable building and bump the version. Keep in mind that we still need package authoring in .NET 8 and older versions. --------- Co-authored-by: Jan Kotas <jkotas@microsoft.com>

davidwrighton · 2026-06-04T22:52:28Z

And make sure all logic run under the crst is safe for running in such a place

Also, add logic to handle some simple cases where moving to preemptive is fairly simple. Notably, the VirtualCallStub logic needed these fixes.

…ore ideal for perfmap scenarios

dotnet-policy-service · 2026-06-04T22:53:48Z

Tagging subscribers to this area: @agocke
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

This PR adjusts CoreCLR’s perfmap logging synchronization to avoid GC-mode toggle deadlocks by switching the PerfMap lock to CRST_UNSAFE_ANYMODE, and updates VSD (virtual call stub) stub-generation paths to safely enter preemptive mode where needed when perfmap logging is enabled.

Changes:

Switch PerfMap’s s_csPerfMap to CRST_UNSAFE_ANYMODE to avoid deadlock cycles involving GC-mode toggles during lock acquisition.
Update VirtualCallStubManager stub-generation call sites to temporarily enter preemptive GC mode when perfmap logging is enabled, and reinitialize hash probers after mode transitions.
Add a non-FEATURE_PERFMAP stub PerfMap implementation in perfmap.h so call sites can compile without #ifdef FEATURE_PERFMAP wrappers.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
src/coreclr/vm/virtualcallstub.cpp	Wrap specific stub-generation paths in `GCX_MAYBE_PREEMP` when perfmap is enabled, and reset probers after potential invalidation.
src/coreclr/vm/perfmap.h	Add a stub `PerfMap` class for builds where `FEATURE_PERFMAP` is not defined.
src/coreclr/vm/perfmap.cpp	Initialize the PerfMap lock as `CRST_UNSAFE_ANYMODE` and slightly reduce time holding the lock in `LogPreCompiledMethod`.

Correct LogStubs contract for use on Windows

Copilot

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

davidwrighton · 2026-06-08T21:45:55Z

/backport to release/10.0

github-actions · 2026-06-08T21:46:03Z

Started backporting to release/10.0 (link to workflow run)

github-actions · 2026-06-08T21:47:41Z

@davidwrighton backporting to release/10.0 failed, the patch most likely resulted in conflicts. Please backport manually!

git am output

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patchApplying: Add logic to handle some simple cases where moving to preemptive is more ideal for perfmap scenariosUsing index info to reconstruct a base tree...M	src/coreclr/vm/perfmap.cppM	src/coreclr/vm/perfmap.hM	src/coreclr/vm/virtualcallstub.cppFalling back to patching base and 3-way merge...Auto-merging src/coreclr/vm/perfmap.cppCONFLICT (content): Merge conflict in src/coreclr/vm/perfmap.cppAuto-merging src/coreclr/vm/perfmap.hAuto-merging src/coreclr/vm/virtualcallstub.cpperror: Failed to merge in the changes.hint: Use 'git am --show-current-patch=diff' to see the failed patchhint: When you have resolved this problem, run "git am --continue".hint: If you prefer to skip this patch, run "git am --skip" instead.hint: To restore the original branch and stop patching, run "git am --abort".hint: Disable this message with "git config set advice.mergeConflict false"Patch failed at 0001 Add logic to handle some simple cases where moving to preemptive is more ideal for perfmap scenariosError: The process '/usr/bin/git' failed with exit code 128

Link to workflow output

@leculver

…129142) Backport of #129021 to release/10.0 Fixes#128401 /cc @leculver ## Customer Impact - [x] Customer reported - [ ] Found internally This was reported by customers which found that a service in production would deadlock occasionally when perfmap generation was enabled. ## Regression - [x] Yes - [ ] No This was introduced in #113943 ## Testing Fix was verified through analysis, and the fix also includes an escape hatch environment variable (DOTNET_PerfMapGranularity=4) which will disable the problematic code entirely. ## Risk 1. This fix is only applicable to customers which use perfmaps 2. The fix not only includes code changes which fix the deadlock problem from happening, but also includes a change to add a config switch to avoid the problematic code entirely while keeping the perfmap generation for most scenarios which are interesting to customers. Risks: This fix adjusts a lock so that it will not switch to preemptive mode, and we will run some file I/O while under that lock. This may cause GC latency spikes on some customer workloads. This issue is mitigated by the new switch which can be used to avoid the problem in its entirety at the cost of slightly less accurate profile data for a limited set of scenarios. **IMPORTANT**: If this backport is for a servicing release, please verify that: - For .NET 8 and .NET 9: The PR target branch is `release/X.0-staging`, not `release/X.0`. - For .NET 10+: The PR target branch is `release/X.0` (no `-staging` suffix). ## Package authoring no longer needed in .NET 9 **IMPORTANT**: Starting with .NET 9, you no longer need to edit a NuGet package's csproj to enable building and bump the version. Keep in mind that we still need package authoring in .NET 8 and older versions. --------- Co-authored-by: Jan Kotas <jkotas@microsoft.com>

davidwrighton · 2026-06-04T22:52:28Z

And make sure all logic run under the crst is safe for running in such a place

Also, add logic to handle some simple cases where moving to preemptive is fairly simple. Notably, the VirtualCallStub logic needed these fixes.

…ore ideal for perfmap scenarios

dotnet-policy-service · 2026-06-04T22:53:48Z

Tagging subscribers to this area: @agocke
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

This PR adjusts CoreCLR’s perfmap logging synchronization to avoid GC-mode toggle deadlocks by switching the PerfMap lock to CRST_UNSAFE_ANYMODE, and updates VSD (virtual call stub) stub-generation paths to safely enter preemptive mode where needed when perfmap logging is enabled.

Changes:

Switch PerfMap’s s_csPerfMap to CRST_UNSAFE_ANYMODE to avoid deadlock cycles involving GC-mode toggles during lock acquisition.
Update VirtualCallStubManager stub-generation call sites to temporarily enter preemptive GC mode when perfmap logging is enabled, and reinitialize hash probers after mode transitions.
Add a non-FEATURE_PERFMAP stub PerfMap implementation in perfmap.h so call sites can compile without #ifdef FEATURE_PERFMAP wrappers.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
src/coreclr/vm/virtualcallstub.cpp	Wrap specific stub-generation paths in `GCX_MAYBE_PREEMP` when perfmap is enabled, and reset probers after potential invalidation.
src/coreclr/vm/perfmap.h	Add a stub `PerfMap` class for builds where `FEATURE_PERFMAP` is not defined.
src/coreclr/vm/perfmap.cpp	Initialize the PerfMap lock as `CRST_UNSAFE_ANYMODE` and slightly reduce time holding the lock in `LogPreCompiledMethod`.

Correct LogStubs contract for use on Windows

Copilot

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

davidwrighton · 2026-06-08T21:45:55Z

/backport to release/10.0

github-actions · 2026-06-08T21:46:03Z

Started backporting to release/10.0 (link to workflow run)

github-actions · 2026-06-08T21:47:41Z

@davidwrighton backporting to release/10.0 failed, the patch most likely resulted in conflicts. Please backport manually!

git am output

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patchApplying: Add logic to handle some simple cases where moving to preemptive is more ideal for perfmap scenariosUsing index info to reconstruct a base tree...M	src/coreclr/vm/perfmap.cppM	src/coreclr/vm/perfmap.hM	src/coreclr/vm/virtualcallstub.cppFalling back to patching base and 3-way merge...Auto-merging src/coreclr/vm/perfmap.cppCONFLICT (content): Merge conflict in src/coreclr/vm/perfmap.cppAuto-merging src/coreclr/vm/perfmap.hAuto-merging src/coreclr/vm/virtualcallstub.cpperror: Failed to merge in the changes.hint: Use 'git am --show-current-patch=diff' to see the failed patchhint: When you have resolved this problem, run "git am --continue".hint: If you prefer to skip this patch, run "git am --skip" instead.hint: To restore the original branch and stop patching, run "git am --abort".hint: Disable this message with "git config set advice.mergeConflict false"Patch failed at 0001 Add logic to handle some simple cases where moving to preemptive is more ideal for perfmap scenariosError: The process '/usr/bin/git' failed with exit code 128

Link to workflow output

@leculver

…129142) Backport of #129021 to release/10.0 Fixes#128401 /cc @leculver ## Customer Impact - [x] Customer reported - [ ] Found internally This was reported by customers which found that a service in production would deadlock occasionally when perfmap generation was enabled. ## Regression - [x] Yes - [ ] No This was introduced in #113943 ## Testing Fix was verified through analysis, and the fix also includes an escape hatch environment variable (DOTNET_PerfMapGranularity=4) which will disable the problematic code entirely. ## Risk 1. This fix is only applicable to customers which use perfmaps 2. The fix not only includes code changes which fix the deadlock problem from happening, but also includes a change to add a config switch to avoid the problematic code entirely while keeping the perfmap generation for most scenarios which are interesting to customers. Risks: This fix adjusts a lock so that it will not switch to preemptive mode, and we will run some file I/O while under that lock. This may cause GC latency spikes on some customer workloads. This issue is mitigated by the new switch which can be used to avoid the problem in its entirety at the cost of slightly less accurate profile data for a limited set of scenarios. **IMPORTANT**: If this backport is for a servicing release, please verify that: - For .NET 8 and .NET 9: The PR target branch is `release/X.0-staging`, not `release/X.0`. - For .NET 10+: The PR target branch is `release/X.0` (no `-staging` suffix). ## Package authoring no longer needed in .NET 9 **IMPORTANT**: Starting with .NET 9, you no longer need to edit a NuGet package's csproj to enable building and bump the version. Keep in mind that we still need package authoring in .NET 8 and older versions. --------- Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Add logic to handle some simple cases where moving to preemptive is m…
4f02657
…ore ideal for perfmap scenarios

CopilotAI review requested due to automatic review settings June 4, 2026 22:52

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github-actionsBot added the area-VM-coreclr label Jun 4, 2026

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davidwrighton mentioned this pull request Jun 5, 2026
Call into PerfMap logic exclusively in preemptive mode #129019
Merged

davidwrighton added 2 commits June 5, 2026 13:59

Code review feedback
4e4a6f6

Add feature to disable reporting of stubs via PerfMap
95630a4
Correct LogStubs contract for use on Windows

CopilotAI review requested due to automatic review settings June 5, 2026 22:17

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Comment threadsrc/coreclr/vm/perfmap.cpp
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davidwrighton added 2 commits June 5, 2026 15:29

Reverse polarity of new flag
fa3cfe6

And update env flag doc in clrconfigvalues.h
2f6a3cd

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davidwrighton merged commit 1b366f4 into dotnet:mainJun 8, 2026
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davidwrighton added a commit to davidwrighton/runtime that referenced this pull request Jun 8, 2026
Backportdotnet#129021to release/10.0
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davidwrighton mentioned this pull request Jun 8, 2026
[release/10.0] : Change the PerfMap crst into an UNSAFE_ANYMODE crst #129142
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dotnet-maestroBot mentioned this pull request Jun 9, 2026
[main] Source code updates from dotnet/runtime dotnet/dotnet#7143
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dotnet-milestone-botBot added this to the 11.0-preview6 milestone Jun 9, 2026

github-actionsBot locked and limited conversation to collaborators Jul 10, 2026