Best Practices for Managing Thread Context and IRQL in KMDF Drivers

To avoid problems related to thread context and IRQL, adopt these practices:

• Unless you are certain that a driver function is called in a particular thread context, never make any assumptions about the contents of the user-mode address space.

• Know which driver functions can be called at IRQL>=DISPATCH_LEVEL and understand the restrictions that running at this level places on driver code.

• Store any data that can be accessed at IRQL>=DISPATCH_LEVEL in nonpaged memory.

  Possible locations are the device object context area, a driver-allocated space in nonpaged pool memory, or the kernel-mode stack.

• Use Driver Verifier, the PAGED_CODE and PAGED_CODE_LOCKED macros, SDV, PREfast for Drivers, and debugger extensions to help find IRQL-related bugs in drivers.

• Test drivers on as many hardware configurations as possible, including multiprocessor systems.