Replace GCX_COOP with EBR for EEHashTable bucket reclamation#124822
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Replace GCX_COOP with EBR for EEHashTable bucket reclamation#124822AaronRobinsonMSFT wants to merge 1 commit intodotnet:mainfrom
AaronRobinsonMSFT wants to merge 1 commit intodotnet:mainfrom
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Pull request overview
This PR replaces the prior GC cooperative-mode based scheme for safely reclaiming obsolete EEHashTable bucket arrays with Epoch-Based Reclamation (EBR), aligning EEHashTable resizing behavior with the earlier HashMap EBR work.
Changes:
- Add a dedicated global EBR collector (
g_EEHashEbr) and initialize it during EE startup; trigger cleanup from the finalizer thread’s “extra work” loop. - Refactor EEHashTable bucket allocation/freeing into helpers and use EBR critical regions + deferred deletion during table growth instead of
GCX_COOP_NO_THREAD_BROKEN+SyncClean. - Simplify
SyncCleanby removing the EEHashTable-specific cleanup list and related APIs.
Reviewed changes
Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.
Show a summary per file
| File | Description |
|---|---|
| src/coreclr/vm/syncclean.hpp | Removes EEHashTable cleanup list API; leaves SyncClean::CleanUp() only. |
| src/coreclr/vm/syncclean.cpp | Removes EEHashTable cleanup list storage and freeing logic. |
| src/coreclr/vm/finalizerthread.cpp | Adds g_EEHashEbr cleanup request detection and processing in finalizer extra-work path. |
| src/coreclr/vm/eehash.inl | Replaces COOP transitions with EBR critical regions; defers old bucket array deletion via EBR during growth. |
| src/coreclr/vm/eehash.h | Declares EEHashTable bucket allocation/free helpers. |
| src/coreclr/vm/eehash.cpp | Implements AllocateEEHashBuckets / FreeEEHashBuckets. |
| src/coreclr/vm/ebr.h | Declares extern EbrCollector g_EEHashEbr. |
| src/coreclr/vm/ebr.cpp | Defines global g_EEHashEbr. |
| src/coreclr/vm/ceemain.cpp | Initializes g_EEHashEbr during EE startup. |
Replace cooperative GC mode transitions (GCX_COOP_NO_THREAD_BROKEN) with Epoch-Based Reclamation for safe deferred deletion of old EEHashTable bucket arrays during resize. - Add dedicated g_EEHashEbr collector (init, cleanup, critical regions) - Add AllocateEEHashBuckets/FreeEEHashBuckets helpers in eehash.cpp - Remove SyncClean::AddEEHashTable and associated cleanup infrastructure - Remove redundant MemoryBarrier before VolatilePtr::Store (release semantics) Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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This was referenced Feb 25, 2026
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Replace cooperative GC mode transitions (
GCX_COOP_NO_THREAD_BROKEN) with Epoch-Based Reclamation for safe deferred deletion of oldEEHashTablebucket arrays during resize.Changes
g_EEHashEbrcollector (separate fromHashMap'sg_HashMapEbr), with initialization inceemain.cppand cleanup inf inalizerthread.cppAllocateEEHashBucketsFreeEEHashBucketshelpers ineehash.cpp, following the same pattern asHashMap'sAllocateBucketsFreeBucketsSyncClean::AddEEHashTableand associated cleanup infrastructure fromsyncclean.cpp/.hppMemoryBarrier()beforeVolatilePtr::Store()— release semantics already provide the ordering guaranteeFollow-up to #124307 (Replace
HashMapCOOP transitions with EBR). Specifically see #124307 (comment).