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Chris LuandGitHub
5d5ea18287
SetVolumeCrowded mutated the crowded map under accessLock.RLock(), while GetWritableVolumeCount reads the same map under RLock() on the Assign hot path. Two concurrent RLock holders with one writing and one reading the map triggers a fatal "concurrent map read and map write" that kills the master process (unrecoverable, bypasses recover). Take the write lock in SetVolumeCrowded instead. This event path is a low-frequency single consumer driven by the crowded-volume event loop, and every other mutation of crowded already holds Lock(); setVolumeCrowded takes no nested locks, so there is no deadlock path. The hot readers (GetWritableVolumeCount, CloneWritableVolumes) keep using RLock. Adds a -race regression test that fails (race detected) on the old RLock and passes with the write lock. Fixes #11211