Interrupt Synchronization
Writing reentrant code that executes at multiple IRQL levels requires attention to proper synchronization. This section examines the issues that arise in this kind of environment.
The Problem
If code executing at two different IRQLs attempts to access the same data structure simultaneously, the structure can become corrupted. Figure 5.1 illustrates the details of this synchronization problem.
To understand the exact problem, consider this sequence of events.
Suppose code executing at a low IRQL decides to modify several fields in the foo data structure. For this example, the code executes to the point where the field foo.x is set to 1.
An interrupt occurs and a higher-IRQL piece of code gets control of the processor. ...
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