TRANSPARENT USER MODE SCHEDULING ON TRADITIONAL THREADING SYSTEMS

• US 20100083275A1
• Filed: 09/30/2008
• Published: 04/01/2010
• Est. Priority Date: 09/30/2008
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Kishan, Arun U., Teixeira, Pedro, Probert, Dave, Jayamohan, Ajith
• Granted Patent: US 8,473,964 B2
• Time in Patent Office: Days
• US Class Current: 718/108
• CPC Class Codes: G06F 13/1626 by reordering requests
• CPC Class Codes: G06F 9/461 Saving or restoring of program or task context
• CPC Class Codes: G06F 9/4843 by program, e.g. task dispatcher, supervisor, operating system
• CPC Class Codes: G06F 9/4881 Scheduling strategies for dispatcher, e.g. round robin, multi-level priority queues
• CPC Class Codes: G06F 9/54 Interprogram communication
• CPC Class Codes: G06F 9/545 where tasks reside in different layers, e.g. user- and kernel-space

Abstract

Embodiments for performing cooperative user mode scheduling between user mode schedulable (UMS) threads and primary threads are disclosed. In accordance with one embodiment, an asynchronous procedure call (APC) is received on a kernel portion of a user mode schedulable (UMS) thread. The status of the UMS thread as it is being processed in a multi-processor environment is determined. Based on the determined status, the APC is processed on the UMS thread.

Claims

1. A method, comprising:

receiving an original asynchronous procedure call (APC) on a kernel portion of a user mode schedulable (UMS) thread;

determining a status of the UMS thread that is being processed in a multi-processor environment; and

processing the original APC on the UMS thread based on the determined status of the UMS thread.

2. The method of claim 1, wherein the status includes one of the UMS thread executing in kernel mode, the UMS thread executing via a primary thread in user mode, the UMS thread engaging in a context migration with the primary thread, and the UMS thread being idle.

3. The method of claim 1, wherein the status includes one of the UMS thread engaging in a context loading with the primary thread and the UMS thread engaging in a context saving with the primary thread, and wherein the primary thread includes first context information from a CPU, and the UMS thread includes second context information from a memory.

4. The method of claim 1, wherein the determining includes determining that the UMS thread is executing in kernel mode, and wherein the execution further comprise executing the original APC on a UMS thread kernel portion to one of retrieve or modify context information of the kernel portion.

5. The method of claim 1, further comprising inserting an identifier (ID) of the primary thread into a client identifier (CID) field of the UMS thread prior to executing the UMS thread via the primary thread in user mode, and wherein the determining includes determining that the UMS thread is associated with the primary thread based on the CID.

6. The method of claim 1, wherein the determining includes determining that the UMS thread is idle, and wherein the processing further comprises:

placing a lock on a UMS thread user portion when the UMS thread is not being executed, the lock preventing the UMS thread from being executed in one of kernel mode or user mode; and

executing the original APC on the UMS thread user portion to one of retrieve or modify context information of the UMS thread user portion.

7. The method of claim 1, wherein the determining includes determining that the UMS thread is executing via a primary thread in user mode, and wherein the processing further comprises:

firing a disassociate APC at the primary thread to cause the primary thread to abandon execution in user mode and return to kernel mode;

returning context information from a primary thread kernel portion to a UMS thread user portion; and

executing the original APC on the UMS thread user portion to one of retrieve or modify the context information of the UMS thread user portion.

8. The method of claim 1, wherein determining includes determining that the UMS thread is engaging in a context migration with a primary thread, and wherein the processing further comprises:

pulling new context information from a primary thread kernel portion to a staging area in a UMS thread kernel portion via an original APC; and

executing the original APC on the UMS thread user portion to one of retrieve or modify the new context information of the UMS thread kernel portion.

9. The method of claim 1, wherein determining includes determining that the UMS thread is engaging in a context migration with a primary thread, and wherein the processing further comprises:

providing an indicator to signal that the primary thread is ready to transfer new context information to the UMS thread in response to an disassociate APC that is generated based on an original APC;

pulling new context information from a primary thread kernel portion to a staging area in a UMS thread kernel portion the an original APC;

replacing old context information of the UMS thread kernel portion with the new context information in the staging area; and

executing the original APC on the UMS thread user portion to one of retrieve or modify the new context information of the UMS thread kernel portion.

10. The method of claim 1, wherein determining includes determining that the UMS thread is engaging in a context loading with a primary thread, and wherein the processing further comprises:

completing a transfer of context information from a UMS thread user portion to a primary thread user portion that is in progress in response to a disassociate APC, the disassociate APC being generated based on an original APC; and

executing the original APC on the UMS thread user portion to one of retrieve or modify the context information of the UMS thread user portion.

11. The method of claim 1, wherein determining includes determining that the UMS thread is engaged in context saving with a primary thread, and wherein the processing further comprises:

completing a replacement of first context information in a UMS thread user portion with second context information from a primary thread user portion in response to a disassociate APC, the disassociate APC being generated based on an original APC;

executing the original APC on the UMS thread user portion to one of retrieve or modify the first context information of the UMS thread user portion; and

repeating the replacement of the first context information in the UMS thread user portion with the second context information from the primary thread user portion.

12. The method of claim 1, wherein determining includes determining that the UMS thread is engaged in context saving with a primary thread as a result of a page fault, and wherein the processing further comprises:

terminating a replacement of first context information in a UMS thread user portion with second context information from a primary thread user portion in response to a disassociate APC, the disassociate APC being generated based on an original APC;

restoring the first context information of the UMS user portion to states prior to the replacement;

executing the original APC on the UMS thread user portion to one of retrieve or modify the first context information of the UMS thread user portion; and

processing a primary thread kernel portion in kernel mode instead of the primary thread user portion in user mode as a result of the page fault.

13. The method of claim 1, wherein the UMS thread includes a data bit to indicate that the UMS thread is executing in kernel mode, and wherein determining includes determining that the UMS thread is executing in kernel mode based on a value of the data bit.

14. The method of claim 1, wherein the UMS thread includes an identifier field to indicate that the UMS thread is switched with a primary thread, and wherein determining includes determining that the UMS thread is switched with the primary thread based on a value of the identifier field.

15. A computer readable medium storing computer-executable instructions that, when executed, cause one or more processors to perform acts comprising:

creating a primary thread from a standard thread, the created primary thread including an original user thread descriptor that resides in the upper portion of a user virtual address (VA) space of the created primary thread; and

creating a duplicate user thread descriptor in a lower portion of the user VA space of the created primary thread when the user thread descriptor is only accessible via a 32-bit data segment,

wherein each of the original user thread descriptor and the duplicate user thread descriptor includes a self-pointer, the self-pointers leading to an identical address in a physical memory.

16. The computer readable medium of claim 15, wherein the upper portion includes an upper 4 gigabyte (GB) portion, and the lower portion includes a lower 4 GB portion.

17. The computer readable medium of claim 15, wherein the 32-bit data segment is implemented on an AMD 64/Intel EM64T architecture.

18. The computer readable medium of claim 15, wherein the standard thread is a NT thread.

19. A system, comprising:

a context holder to store privileged hardware states of a UMS thread;

a primary thread to enter kernel mode via a system call;

a user mode scheduler to replace first context information of the primary thread kernel portion with second context information from the UMS thread kernel portion,

wherein the primary thread is configured to load the stored privileged hardware states into its primary thread kernel portion after the replacement of the first context information with the second context information.

20. The system of claim 19, wherein the privileged hardware states include debug register states.