Method and system for protecting shared code and data in a multitasking operating system

A computer-readable medium whose contents cause a computer system to handle a call to an application programming interface routine of a preemptive multitasking subsystem of an operating system, the operating system also having a cooperative multitasking subsystem, by:

• receiving a call to the application programming interface routine by an application executing in the preemptive multitasking subsystem of the operating system;
• determining that the routine is implemented in the cooperative multitasking subsystem;
• in response to the receiving and determining steps, thunking the call by:
• converting the call to the application programming interface routine in the preemptive multitasking subsystem into a call to the implementation of the application programming interface routine in the cooperative multitasking subsystem;
• obtaining ownership of a synchronization mechanism regulating the invocation of all application programming interface routine implementations ih the cooperative multitasking subsystem;
• and
• only after ownership of the synchronization mechanism has been obtained, calling the implementation of the application programming interface routine in the cooperative multitasking subsystem using the converted call.

A computer-readable medium having computer-executable instructions which are configured to, when executed, implement a thunk layer for handling a call to an application programming interface routine of a preemptive multitasking subsystem of an operating system that is implemented in the cooperative multitasking subsystem, the operating system also having a cooperative multitasking subsystem, comprising:

• a call receiver that received a call to the application programming interface routine by an application executing in the preemptive multitasking subsystem of the operating system;
• a call converter that converts the call to the application programming interface routine in the preemptive multitasking subsystem into a call to the implementation of the application programming interface routine in the cooperative multitasking subsystem;
• a synchronization mechanism regulating the invocation of all application programming interface routine implementations in the cooperative multitasking subsystem;
• and
• a call initiator that calls the implementation of the application programming interface routine in the cooperative multitasking subsystem using the converted call only after ownership of the synchronization mechanism has been obtained.

A computer system having a computer-readable medium whose contents cause the computer system to handle a call to an application programming interface routine of a preemptive multitasking subsystem of an operating system, the operating system also having a cooperative multitasking subsystem, comprising:

• a call receiver adapted to receive a call to the application programming interface routine by an application executing in the preemptive multitasking subsystem of the operating system and determine whether the routine is implemented in the cooperative multitasking subsystem;
• a thunk layer adapted to, where the call received by the call receiver is determined to be implemented in the cooperative multitasking subsystem, thunk the call by:
• converting the call to the application programming interface routine in the preemptive multitasking subsystem into a call to the implementation of the
• application programming interface routine in the cooperative multitasking subsystem;
• obtaining ownership of a synchronization mechanism regulating the invocation of all application programming interface routine implementations in the cooperative multitasking subsystem;
• and
• only after ownership of the synchronization mechanism has been obtained, calling the implementation of the application programming interface routine in the cooperative multitasking subsystem using the converted call.