Understanding Locking

The information in this section is provided to assist you in understanding locking.

Lockl Locks
The lockl locks (previously called conventional locks) are provided for compatibility only and should not be used in new code: simple or complex locks should be used instead. These locks are used to protect a critical section of code which accesses a resource such as a data structure or device, serializing access to the resource. Every thread which accesses the resource must acquire the lock first, and release the lock when finished.
Simple Locks
A simple lock provides exclusive-write access to a resource such as a data structure or device.
Complex Locks
A complex lock can provide either shared or exclusive access to a resource such as a data structure or device.
Types of Critical Sections
There are two types of critical sections which must be protected from concurrent execution in order to serialize access to a resource.
Priority Promotion
When a lower priority thread owns a lock which a higher-priority thread is attempting to acquire, the owner has its priority promoted to that of the most favored thread waiting for the lock.
Locking Strategy in Kernel Mode
A hierarchy of locks exists. This hierarchy is imposed by software convention, but is not enforced by the system. The lockl kernel_lock variable, which is the global kernel lock, has the coarsest granularity. Other types of locks have finer granularity.

Parent topic: Kernel Environment

Related concepts

System Calls