REUSABLE, OPERATING SYSTEM AWARE HARDWARE MUTEX

• US 20080005741A1
• Filed: 08/01/2006
• Published: 01/03/2008
• Est. Priority Date: 06/28/2006
• Status: Active Grant

• Current Assignee: NVIDIA Corporation
• Original Assignee: Portal Player Incorporated
• Inventors: Terrell, James R.
• Granted Patent: US 8,321,872 B2
• Time in Patent Office: Days
• US Class Current: 718/102
• CPC Class Codes: G06F 9/526 Mutual exclusion algorithms

Abstract

Hardware resources sharing for a computer system running software tasks. A controller stores records including a mutex ID tag and a waiter flag in a cache. Lock and unlock registers are readable by the controller and loadable by the tasks with a mutex ID specifying a hardware resource. The controller monitors whether the lock register for loading with a mutex ID, and then determines whether it corresponds with the tag of a record in the cache. If so, it sets the record'"'"'s waiter flag. If not, it adds a record having a tag corresponding with the mutex ID. The controller also monitors whether the unlock register for loading with a mutex ID, and then determines whether it corresponds with the tag of a record in the cache. If so, it determines whether that record'"'"'s waiter flag is set and, if so, it clears that record from the cache.

Claims

1. A system for sharing a plurality of hardware resources in a computer system able to run a plurality of software tasks, comprising:

(a) a mutexes controller having a locked mutex cache to store a list of records each including a mutex ID tag and a waiter flag;

(b) a lock register and an unlock register that are each read able by said mutexes controller and load able by the software tasks with a mutex ID specifying one of the hardware resources; and

(c) said mutexes controller being further to;

(1) monitor whether said lock register has been loaded with a said mutex ID and then;

(A) determine whether said mutex ID corresponds with a said mutex ID tag of a said record present in said locked mutex cache; and

(B) if so, to set said waiter flag of said record;

or

(C) if not so, to add a said record to said locked mutex cache having a said mutex ID tag that corresponds with said mutex ID; and

(2) monitor whether said unlock register has been loaded with a said mutex ID and then;

(A) determine whether said mutex ID corresponds with a said mutex ID tag of a said record presently in said locked mutex cache; and

(B) if so, determine whether said waiter flag of said record is set and, if so, to clear said record from said locked mutex cache.

2. The system of claim 1, further comprising a clear waiter register that is load able by the software tasks with a said mutex ID, and wherein said mutexes controller is further to monitor whether said clear waiter register has been loaded with a said mutex ID and then determine whether said mutex ID corresponds with a said mutex ID tag of a said record in said locked mutex cache and reset said waiter flag of such said record.

3. The system of claim 1, wherein the computer system has an operating system and said mutexes controller is further to assert an interrupt to said operating system, and further comprising an active mutex register that is that is load able by said mutexes controller and read able by said operating system.

4. The system of claim 3, wherein said mutexes controller is further at said (c)(1)(B) to load said mutex ID into said active mutex register and assert said interrupt, thereby communicating to said operating system a request for conventional handling of said one of the hardware resources.

5. The system of claim 3, wherein said mutexes controller is further at said (c)(1)(C) to determine if said locked mutex cache is full of said records and, if so, to load an error indication into said active mutex register and assert said interrupt.

6. The system of claim 3, further comprising an interrupt on free flag that is set able by said operating system, and wherein said mutexes controller is further at said (c)(2)(B) to check said interrupt on free flag and assert said interrupt.

7. A process for locking a mutex that controls access to a shared resource by software tasks running under an operating system, the process comprising:

(a) monitoring a lock register for a mutex ID having been loaded there in by one of the software tasks;

(b) determining whether said mutex ID corresponds with a mutex ID tag of a record in a locked mutex cache;

(c) if so;

(1) setting a waiter flag of said record; and

(2) communicating to said operating system a request for conventional handling of the shared resource; and

(d) if not so, adding a new said record to said locked mutex cache with a said mutex ID tag corresponding with said mutex ID, without interrupting the software tasks or the operating system.

8. The process of claim 7, further comprising, prior to said (a), setting parameters for the mutex in registers accessible to the operating system for use by the operating system after said (c)(2).

9. The process of claim 7, wherein said (c)(2) includes:

loading said mutex ID into an active mutex register that is read able by the operating system; and

asserting an interrupt.

10. The process of claim 7, wherein said (d) includes determining if said locked mutex cache is full of said records and, if so:

loading an error indication into an active mutex register; and

asserting an interrupt.

11. The process of claim 7, wherein the operating system is a real-time type operating system.

12. A process for unlocking a mutex that controls access to a shared resource by software tasks running under an operating system, the process comprising:

(a) monitoring an unlock register for a mutex ID having been loaded there in by one of the software tasks;

(b) determining whether said mutex ID corresponds with a mutex ID tag of a record in a locked mutex cache;

(c) if said mutex ID corresponds with a said record;

(1) determining whether a waiter flag of said record is set;

(A) if said waiter flag is set, asserting an interrupt;

(B) if said waiter flag is not set, clearing said record from said locked mutex cache; and

(d) if said mutex ID does not correspond with a record, asserting an interrupt.

13. The process of claim 12, wherein said (c)(1)(B) includes determining whether an interrupt on free flag is set and, if so, asserting an interrupt.

14. The process of claim 12, further comprising:

monitoring a clear waiter register for a mutex ID having been loaded there in by one of the software tasks; and

determining whether said mutex ID corresponds with a said mutex ID tag of a said record in said locked mutex cache and resetting said waiter flag of such said record.

15. The process of claim 12, wherein the operating system is a real-time type operating system.