Mutex Locking

Mutex locking is a synchronization mechanism used in smart contracts to ensure that only one execution flow can access a specific function or state at a time. In the context of DeFi, this is the primary tool for implementing reentrancy guards, where a boolean flag is set to true when a function starts and reset to false when it finishes.

If a second call attempts to enter the function while the flag is true, the transaction is reverted, protecting the protocol's state. This is essential for ensuring that financial calculations, such as interest accruals or collateral valuations, remain atomic and consistent.

It prevents the interleaving of operations that could lead to double-spending or incorrect balance updates. While effective, developers must ensure that locks are correctly implemented to avoid permanent state deadlocks.