How do you lock a skip list for concurrent inserts without rotations blocking readers?

Each node has a lock only on its forward pointers, not the node itself. An inserter locks the predecessor pointers it will modify, inserts at the base level, then unlocks before promoting—readers never block on insertion. Compare this to tree rotations, which need to lock multiple parent-child relationships simultaneously. The simplicity is why lock-free skip list implementations (CAS loops, no mutexes) are so much more practical than lock-free trees.

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