US 6,275,857 B1Granted

System and method for freeing shared resources in a computer system

AssigneeMicrosoft Corporation

InventorColin McCartney

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Abstract

The present invention relates to systems and methods for freeing shared resources that remain allocated to a particular resource allocating process after the resource allocating process has terminated The invention is useful in a computer system where shared hardware is accessed via a shared hardware driver layer The shared hardware driver layer interfaces with either a shared API layer or a nonshared API layer. Processes wishing to access the shared hardware access the hardware through either the shared or nonshared API layer. To release resources and destroy objects in either the shared API layer or the shared hardware driver layer, the present invention uses a helper process that cleans up after termination of the resource allocation process. The helper process first calls, cleanup function in the shared API layer to release resources and destroy objects in the shared API layer and associated hardware driver. The helper process then loads a copy of the nonshared API layer and makes a call to a similar cleanup function to release any remaining resources and destroy any remaining objects. In the alternative, the helper process loads a copy of the nonshared API layer and calls to the similar cleanup function are made by the cleanup function in the shared API layer.

Claims26

Dependent claims

A method of freeing shared system resources shared among a plurality of processes running on a computer system having a central processing unit (CPU), a portion of said shared system resources being allocated for use by a process either through a shared application program interface that provides an interface to a shared hardware driver and is shared among said plurality of processes or through a local application program interface that provides an interface to a shared hardware driver and is not shared among said plurality of processes, said method comprising the steps of:

experiencing termination of said process running on the computer system, the termination being such that the portion of the shared system resources remain allocated to the terminated process by at least one of the shared application program interface and the shared hardware driver after said termination, the portion of the shared system resources further being associated with freed system resources that were allocated to the process by the local application program interface prior to said termination and have been freed upon said termination such that the freed system resources are undefined with respect to the portion of the shared system resources;
starting a helper process that frees the portion of the shared system resources that are allocated to the terminated process by performing at least one of the following steps:
calling at least one function in said shared application program interface that frees said portion of the shared system resources without attempting to reference said freed system resources associated with said portion of the shared system resources, wherein said portion of the shared system resources are available for allocation to another process;
and
calling at least one function in said local application program interface that frees said portion of the shared system resources without attempting to reference said freed system resources associated with said portion of the shared system resources, wherein said portion of the shared system resources are available for allocation to another process.

2 more elements

A computer-readable medium having computer-executable instructions comprising:

a helper process that is invoked at a computer system when a resource allocating process running at said computer system terminates without fully freeing shared system resources allocated to the resource allocating process by at least one of a shared application program interface (API) and a shared hardware driver, wherein the shared system resources include at least one of a driver resource and a shared API resource and wherein the driver resource is linked to at least one of a local resource and the shared API resource, the helper process including at least one of:
program code means for calling at least one function in the shared application program interface, which provides an interface to the shared hardware driver, said at least one function freeing at least one of the shared API resource and the driver resource allocated by said resource allocating process through said shared application program interface without attempting to reference the freed local resource that was allocated to the terminated process by a nonshared application program interface prior to termination of the process, was freed at said termination, and is associated with said shared system resources;
and
program code means for calling at least one function in the nonshared application program interface, which provides an interface to the shared hardware driver, said at least one function freeing the driver resource allocated by said resource allocating process through said nonshared application program interface without attempting to reference the freed local resource that was allocated to the terminated process by the nonshared application program interface prior to termination of the process, was freed at said termination, and is associated with said shared system resources.

1 more element

In a system including shared hardware accessed by a shared hardware driver, wherein the shared hardware driver includes a driver resource that may be allocated to one or more processes, wherein the shared hardware driver and the driver resource is accessible by a shared application programming interface (API) and a local API, wherein the shared API includes shared resources that may be allocated to the one or more processes and wherein the local API includes local resources that are specific to a particular process, and wherein the particular process allocates resources including one or more of a portion of the shared resource, a portion of the local resource, and a portion of the driver resource during execution of the particular process, a method for freeing the allocated resources when the particular process terminates, wherein the portion of the local resource is freed when the particular process terminates and the portion of the driver resource and the portion of the shared resource remain allocated to the particular process when the particular process terminates, the method comprising acts of:

starting a helper process for freeing the portion of the shared resource and the portion of the driver resource when the particular process terminates;
freeing the portion of the shared resource and the portion of the driver resource by the helper process without accessing the portion of the local resource that is referenced by the shared resource, the portion of the local resource being free and undefined with respect to the portion of the shared resource and to the portion of the driver resource;
when the portion of the driver resource is allocated by the local API:
loading the local API into an address space of the helper process;
and
calling a function of the local API that frees the portion of the driver resource without accessing the portion of the local resource that is referenced by the portion of the driver resource, the portion of the local resource being free and undefined with respect to the portion of the driver resource.

3 more elements

Dependencies are inferred from the claim text.