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Read-copy-update (RCU) operations with reduced memory barrier usage

  • US 7,818,306 B2
  • Filed: 04/21/2007
  • Issued: 10/19/2010
  • Est. Priority Date: 03/24/2006
  • Status: Active Grant
First Claim
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1. A method comprising:

  • to update contents of a section of memory,copying a global flip-counter bit to a local flip-counter bit, the global flip-counter bit specifying which of a first set of per-processor counters and a second set of per-processor counters is a current set of per-processor counters and which is a last set of per-processor counters, the global flip-counter-bit also specifying which of a first set of per-processor need-memory-barrier bits and a second set of per-processor need-memory-barrier bits is a current set of per-processor need-memory-barrier bits and which is a last set of per-processor need-memory-barrier bits;

    where attempting to acquire a flip-counter-bit lock on the global-flip-counter bit is successful, where the global flip-counter bit has not changed while acquiring the flip-counter-bit lock, where all of the last set of per-processor need-memory-barrier bits are equal to a first predetermined value, and where a sum of all of the last set of per-processor counters is equal to a second predetermined value,incrementing each of the last set of per-processor need-memory-barrier bits, using the local flip-counter bit;

    sending an inter-processor interrupt to execute a memory barrier if needed;

    where all of the last set of per-processor need-memory-barrier bits are equal to a second predetermined value,setting each of the current set of per-processor need-memory-barrier bits to zero, using the local flip-counter bit,inverting the global flip-counter bit; and

    ,releasing the flip-counter-bit lock.

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