Kernel lock validator

From Ingo Molnar and Arjan van de Ven

• Adds instrumentation to kernel locking code

• Detect violations of locking rules during system life, such as:

• Locks acquired in different order (keeps track of locking sequences and compares them).
• Spinlocks acquired in interrupt handlers and also in process context when interrupts are enabled.

• Not suitable for production systems but acceptable overhead in development.

See Documentation/lockdep-design.txt for details