Synchronizing communication over shared memory

• US 8,555,292 B2
• Filed: 06/27/2008
• Issued: 10/08/2013
• Est. Priority Date: 06/27/2008
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Haba, Erez
• Primary Examiner(s): Ho, Andy
• Assistant Examiner(s): Kraft, Shih-Wei
• Application Number:
  US12/147,531
• Publication Number:
  US 20090328059A1
• Time in Patent Office: 1,929 Days
• Field of Search: None
• US Class Current: 719/312
• CPC Class Codes: G06F 9/544 Buffers; Shared memory; Pipes

Abstract

Two threads may communicate via shared memory using two different modes. In a polling mode, a receiving thread may poll an indicator set by the sending thread to determine if a message is present. In a blocking mode, the receiving thread may wait until a synchronization object is set by the sending thread which may cause the receiving thread to return to the polling mode. The polling mode may have low latency buy may use processor activity of the receiving thread to repetitively check the indictor. The blocking mode may have a higher latency but may allow the receiving thread to enter a sleep mode or perform other activities.

Claims

1. A method of communicating between a sender thread and a receiving thread through shared memory, the method comprising:

sending a first message by said sender thread by a polling transmission method comprising;

storing said first message;

changing a transmit index; and

forcing a purge of a second memory pipeline for said sender thread after said changing said transmit index;

receiving said first message by said receiving thread by a polling receiving method comprising;

reading said transmit index to determine that said first message is ready to be read; and

reading said first message;

changing to a synchronization object receiving method by said receiving thread by a first changeover method comprising;

forcing a purge of a first memory pipeline for said receiving thread prior to setting a wait object;

setting said wait object, said wait object being an indicator that said receiving thread is not polling for messages;

transmitting a second message by said sender thread by a synchronization object transmission method comprising;

detecting that said wait object is set;

setting an awake object;

storing said second message; and

changing said transmit index;

determining that no new messages are available; and

changing from a synchronization object receiving method by said receiving thread to said polling transmission method by a second changeover method comprising;

receiving said awake object; and

executing said polling receiving method.

2. The method of claim 1, said changing said transmit index comprising toggling said transmit index.

3. The method of claim 1, said changing said transmit index comprising incrementing said transmit index.

4. The method of claim 3, said transmit index comprising a first pointer to a buffer.

5. The method of claim 4, said polling transmission method further comprising:

storing a second pointer in said buffer, said second pointer comprising an address to said first message.

6. The method of claim 4, said buffer being a circular buffer.

7. The method of claim 1, said polling receiving method further comprising:

comparing said transmit index to a receive index to determine said first message is ready to be read.

8. The method of claim 7, said polling receiving method further comprising:

incrementing said receive index after said reading said first message from said shared memory.

9. A system comprising:

a first thread;

a second thread;

a shared memory capable of being accessed by said first thread and said second thread;

one of said first thread and said second thread being a sender thread and the other of said first thread and said second thread being a receiving thread, said sender thread and said receiving thread being configured to communicate using a method comprising;

sending a first message by said sender thread by a polling transmission method comprising;

storing said first message in said shared memory;

changing a transmit index; and

forcing a purge of a second memory pipeline for said sender thread after said changing said transmit index;

receiving said first message by said receiving thread by a polling receiving method comprising;

reading said transmit index to determine that said first message is ready to be read; and

reading said first message from said shared memory;

changing to a synchronization object receiving method by said receiving thread by a first changeover method comprising;

forcing a purge of a first memory pipeline for said receiving thread prior to setting a wait object;

setting said wait object, said wait object being an indicator that said receiving thread is not polling for messages;

transmitting a second message by said sender thread by a synchronization object transmission method comprising;

detecting that said wait object is set;

setting an awake object;

storing said second message in said shared memory; and

changing said transmit index;

determining that no new messages are available; and

changing from a synchronization object receiving method by said receiving thread to said polling transmission method by a second changeover method comprising;

receiving said awake object; and

executing said polling receiving method.

10. The system of claim 9, said first thread being said sender thread and said second thread being said receiving thread.

11. The system of claim 10, said second thread being configurable as said sender thread and said first thread being configurable as said receiving thread.

12. The system of claim 9, said changing said transmit index comprising incrementing said transmit index.

13. The system of claim 12, said transmit index comprising a first pointer to a buffer.

14. The system of claim 13, said polling transmission method further comprising:

storing a second pointer in said buffer, said second pointer comprising an address to said first message.

15. The system of claim 14, said buffer being a circular buffer.

16. A method of communicating between a sender thread and a receiving thread through shared memory, the method comprising:

sending a first message by said sender thread by a polling transmission method comprising;

storing said first message in said shared memory;

storing a pointer to said first message in a first register of a first buffer;

changing a transmit index to indicate said first register of said first buffer; and

purging a memory pipeline of said sender thread after said changing said transmit index;

receiving said first message by said receiving thread by a polling receiving method comprising;

reading said transmit index;

reading a receive index;

comparing said transmit index to said receive index to determine that said transmit index and said receive index are different;

incrementing said receive index;

reading said first register from said first buffer, said first register corresponding to said receive index; and

reading said first message from said shared memory;

changing to a synchronization object receiving method by said receiving thread by a first changeover method comprising;

forcing a purge of a second memory pipeline for said receiving thread prior to setting a wait object;

setting said wait object, said wait object being an indicator that said receiving thread is not polling for messages;

transmitting a second message by said sender thread by a synchronization object transmission method comprising;

detecting that said wait object is set;

setting an awake object;

storing said second message in said shared memory; and

changing said transmit index;

determining that no new messages are available; and

changing from a synchronization object receiving method by said receiving thread to said polling transmission method by a second changeover method comprising;

receiving said awake object; and

executing said polling receiving method.