OS X and iOS Kernel Programming

Summary

• A driver runs in a multithreaded environment.
• The methods of a driver class can potentially be called from an arbitrary thread. This means that, even if a driver creates no threads of its own, it cannot escape the need for synchronized access to its shared instance variables and hardware.
• The I/O Kit provides synchronization functions that a driver can use to prevent multiple threads from modifying shared data at the same time.
• A spin lock is a suitable synchronization mechanism for code that will hold the lock only for a short period of time or for code that will execute inside a primary interrupt handler.
• A mutex is a better choice if the lock will be held for longer periods, but it cannot be used inside a primary interrupt handler. ...