fix: race condition in Tree.FindEntry() and Tree.entry()#1922
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majiayu000 wants to merge 2 commits intogo-git:mainfrom
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fix: race condition in Tree.FindEntry() and Tree.entry()#1922majiayu000 wants to merge 2 commits intogo-git:mainfrom
majiayu000 wants to merge 2 commits intogo-git:mainfrom
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Add sync.Once for the entry name map (t.m) in entry() and sync.Mutex for the tree path cache (t.t) in FindEntry() to make concurrent access to the same Tree instance thread-safe. Fixes go-git#1917 Signed-off-by: majiayu000 <1835304752@qq.com>
Remove pre-warming that populated caches before the concurrent phase, making the race detector ineffective. Use top-level entry names and a start barrier (sync.WaitGroup gate) so all goroutines begin simultaneously, exercising concurrent t.m and t.t cache initialization. Signed-off-by: majiayu000 <1835304752@qq.com>
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Fixes #1917
Summary
Three data races exist on the
Treestruct whenFindEntry()is called concurrently:FindEntry()readt.t == niland writet.t = make(...)without synchronizationentry()race on the nil-check andbuildMap()callt.mwhile another is still populating it viabuildMap()Approach
sync.Oncefort.m(Races 2 & 3): Replace the nil-check-then-buildMap pattern inentry()witht.mOnce.Do(t.buildMap). buildMap is a one-time lazy init from immutableEntries, sosync.Onceis the idiomatic solution with zero overhead after first call. Reset inDecode()wheret.mis set to nil.sync.Mutexfort.t(Race 1): Protect accesses to the tree path cache with fine-grained locking. I/O operations (tree.dir()) happen outside the lock to preserve concurrency.Both caches are preserved — no performance regression (ref: #1238 was rejected for removing caches, causing 24x regression).
Test Plan
TestFindEntryConcurrent— spawns 10 goroutines callingFindEntryconcurrently on the sameTreeinstance, verifying both same-entry and different-entry access patterns-raceflag