Fix deadlock in NamespacedHierarchicalStore.computeIfAbsent()#5348
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mpkorstanje merged 7 commits intoFeb 11, 2026
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Thanks for taking care of this! The reasoning makes sense to me. I only added a few nitpicks regarding explanatory comment.
Co-authored-by: Marc Philipp <mail@marcphilipp.de>
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In #5231 evaluation of the default value creator was deferred until after an entry was created in the concurrent hash map backing the store. This enables recursive updates. However, by calling `evaluateIfNotNull` inside `compute` threads that lost the race would wait inside `Map::compute` for the value to be evaluated. Waiting here is a problem when the backing concurrent hashmap is reaching capacity. The thread waiting inside compute holds a lock while at the same time the thread that won the race will try to acquire a lock to resize the map. By making the threads that lost the race wait outside of `Map::compute` we can prevent this dead lock. This does require that each thread retries when another thread failed to insert a value. But eventually either one other thread either successfully inserts a value or the thread uses its own default value creator. Fixes: #5346 Co-authored-by: Marc Philipp <mail@marcphilipp.de> (cherry picked from commit f29de38)
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In #5231 evaluation of the default value creator was deferred until after an entry was created in the concurrent hash map backing the store. This enables recursive updates. However, by calling `evaluateIfNotNull` inside `compute` threads that lost the race would wait inside `Map::compute` for the value to be evaluated. Waiting here is a problem when the backing concurrent hashmap is reaching capacity. The thread waiting inside compute holds a lock while at the same time the thread that won the race will try to acquire a lock to resize the map. By making the threads that lost the race wait outside of `Map::compute` we can prevent this dead lock. This does require that each thread retries when another thread failed to insert a value. But eventually either one other thread either successfully inserts a value or the thread uses its own default value creator. Fixes: #5346 Co-authored-by: Marc Philipp <mail@marcphilipp.de> (cherry picked from commit f29de38)
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In #5231 evaluation of the default value creator was deferred until after an entry was created in the concurrent hash map backing the store. This enables recursive updates. However, by calling
evaluateIfNotNullinsidecomputethreads that lost the race would wait insideMap::computefor the value to be evaluated.junit-framework/junit-platform-engine/src/main/java/org/junit/platform/engine/support/store/NamespacedHierarchicalStore.java
Lines 272 to 280 in bfd70fd
Waiting here is a problem when the backing concurrent hashmap is reaching capacity. The thread waiting inside compute holds a lock while at the same time the thread that won the race will try to acquire a lock to resize the map.
By making the threads that lost the race wait outside of
Map::computewe can prevent this dead lock. This does require that each thread retries when another thread failed to insert a value. But eventually either one other thread either successfully inserts a value or the thread uses its own default value creator.Fixes: #5346
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@APIannotations