Fix deadlock in NamespacedHierarchicalStore.computeIfAbsent() by mpkorstanje · Pull Request #5348 · junit-team/junit-framework (original) (raw)
Co-authored-by: Marc Philipp mail@marcphilipp.de
marcphilipp pushed a commit that referenced this pull request
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)
marcphilipp pushed a commit that referenced this pull request
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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