Mutators only trigger VM_G1CollectForAllocation safepoint after failing to allocate. However, in the safepoint, without any intervening GC completed, VM_G1CollectForAllocation allocation attempts may succeed without completing a GC. This is because an active GCLocker may force expansion of the eden regions while the VM_G1CollectForAllocation is stalling waiting to execute.

This is rare sequence of events, and should be highlighted with a comment. Additionally, if GCLocker is eventually removed, this allocation attempt should also be removed.