MT SAFE Modules Using Explicit Locks
Although the result is not reliable, you can use explicit locks either instead of perimeters or to augment the concurrency restrictions provided by the perimeters.
 | Caution - Explicit locks cannot be used to preserve message ordering in a module because of the risk of re-entering the module. Use MT STREAMS perimeters to preserve message ordering. |
All four types of kernel synchronization primitives are available to the module writer: mutexes, readers/writer locks, semaphores, and condition variables. Because cv_wait implies a context switch, it can only be called from the module's open and close procedures, which are executed with valid process context. You must use the synchronization primitives to protect accesses and ensure the integrity of private module data structures.