STALE POINTER DETECTION WITH OVERLAPPING VERSIONED MEMORY

• US 20140156908A1
• Filed: 11/30/2012
• Published: 06/05/2014
• Est. Priority Date: 11/30/2012
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Prakash, Raj, Lobo, Sheldon M.
• Granted Patent: US 9,519,592 B2
• Time in Patent Office: Days
• US Class Current: 711/6
• CPC Class Codes: G06F 12/10 Address translation
• CPC Class Codes: G06F 12/1416 by checking the object accessibility, e.g. type of access defined by the memory independently of subject rights G06F12/1458 takes precedence
• CPC Class Codes: G06F 2212/65 Details of virtual memory and virtual address translation
• CPC Class Codes: G06F 2212/657 Virtual address space management

Abstract

In general, in one aspect, the invention relates to a method for managing virtual memory (VM). The method includes receiving, from an application, a first access request comprising a first VM address identifying a VM location, obtaining a current VM location version value for the VM location, obtaining a first submitted VM location version value from the first VM address, and in response to a determination that the current VM location version value and the first submitted VM location version value match: servicing the first access request using the first VM address.

Claims

1. A method for managing virtual memory (VM) comprising:

receiving, from an application, a first access request comprising a first VM address identifying a VM location;

obtaining a current VM location version value for the VM location;

obtaining a first submitted VM location version value from the first VM address; and

in response to a determination that the current VM location version value and the first submitted VM location version value match;

servicing the first access request using the first VM address.

2. The method of claim 1, further comprising:

receiving, from the application, a second access request comprising a second VM address identifying the VM location;

obtaining the current VM location version value for the VM location;

obtaining a second submitted VM location version value from the second VM address; and

in response to a determination that the current VM location version value and the second submitted VM location version value do not match;

sending an error to the application.

3. The method of claim 1, further comprising:

receiving, from the application, a notification that the VM location is no longer in use, wherein the notification comprises the first VM address;

adding the first VM address to a freed VM location list.

4. The method of claim 3, further comprising:

receiving, from the application, an allocation request;

obtaining the first VM address from the freed VM location list;

incrementing the current VM location version value to obtain an updated VM location version value; and

generating a second VM address using the first VM address and the updated VM location version value.

5. The method of claim 4, further comprising:

receiving, from the application, a second access request comprising the second VM address identifying the VM location;

obtaining the updated VM location version value for the VM location;

obtaining a second submitted VM location version value from the second VM address; and

in response to a determination that the current VM location version value and the second submitted VM location version value match;

servicing the second access request using the second VM address.

6. The method of claim 1, wherein servicing the first access request using the physical memory address comprises:

translating the first VM address to obtain a physical memory address, wherein the physical memory address is mapped to the VM location.

7. The method of claim 6,

wherein the first VM address comprises the first submitted VM location version value;

and

wherein translating the first VM address to obtain the physical memory address comprises disregarding the first submitted VM location version value.

8. The method of claim 7, wherein the first VM address is translated directly without removing the first submitted VM location version value.

9. The method of claim 1, wherein servicing the first access request using the first VM address comprises one selected from a group consisting of writing data at the VM location identified by the first VM address and reading data from the VM location identified by the first VM address.

10. A non-transitory computer readable medium comprising instructions that, when executed by a processor, perform a method for managing virtual memory (VM), the method comprising:

receiving, from an application, a first access request comprising a first VM address identifying a VM location;

obtaining a current VM location version value for the VM location;

obtaining a first submitted VM location version value from the first VM address; and

in response to a determination that the current VM location version value and the first submitted VM location version value match;

service the first access request using the first VM address.

11. The non-transitory computer readable medium of claim 10, the method further comprising:

receiving, from the application, a second access request comprising a second VM address identifying the VM location;

obtaining the current VM location version value for the VM location;

obtaining a second submitted VM location version value from the second VM address; and

in response to a determination that the current VM location version value and the second submitted VM location version value do not match;

sending an error to the application.

12. The non-transitory computer readable medium of claim 10, the method further comprising:

receiving, from the application, a notification that the VM location is no longer in use, wherein the notification comprises the first VM address;

adding the first VM address to a freed VM location list.

13. The non-transitory computer readable medium of claim 10, the method further comprising:

receiving, from the application, an allocation request;

obtaining the first VM address from the freed VM location list;

incrementing the current VM location version value to obtain an updated VM location version value; and

generating a second VM address using the first VM address and the updated VM location version value.

14. The non-transitory computer readable medium of claim 10, the method further comprising:

receiving, from the application, a second access request comprising the second VM address identifying the VM location;

obtaining the updated VM location version value for the VM location;

obtaining a second submitted VM location version value from the second VM address; and

in response to a determination that the current VM location version value and the second submitted VM location version value match;

service the second access request using the second VM address.

15. The non-transitory computer readable medium of claim 10, wherein servicing the first access request using the first VM address comprises:

translating the first VM address to obtain a physical memory address, wherein the physical memory address is mapped to the VM location.

16. The non-transitory computer readable medium of claim 15,

wherein the first VM address comprises the first submitted VM location version value;

and

wherein translating the first VM address to obtain the physical memory address comprises disregarding the first submitted VM location version value.

17. The non-transitory computer readable medium of claim 16,

wherein the first VM address is translated directly without removing the first submitted VM location version value.

18. The non-transitory computer readable medium of claim 10, wherein servicing the first access request using the first VM address comprises one selected from a group consisting of writing data at the VM location identified by the first VM address and reading data from the VM location identified by the first VM address.

19. A system comprising:

physical memory;

a virtual memory (VM) manager configured to;

receive, from an application, an access request comprising a VM address corresponding to a VM location;

obtain a current VM location version value for the VM location;

obtain a submitted VM location version value from the VM address;

a central processing unit configured to;

in response to a determination that the current VM location version value and the submitted VM location version value match, service the access request using the VM address.

20. The system of claim 19, further comprising:

a memory management unit (MMU) configured to;

translate the VM address to obtain a physical memory address corresponding to a location in the physical memory, wherein the physical memory address is mapped to the VM location.