Patent ID: 7395263

Claim:
A method for realtime-safe detection of a grace period for deferring the destruction of a shared data element until pre-existing references to the data element are removed, comprising: establishing a pair of counters for each of one or more processors; establishing a global counter selector that determines which counter of each per-processor counter pair is a current counter; when reading a shared data element at a processor: incrementing the current counter of said processor's counter pair that corresponds to said global counter selector; testing for reversal of said processor's counter pair to ensure that the incremented counter is still the current counter corresponding to said global counter selector; if a counter pair reversal has occurred such that said incremented counter has become the non-current counter, incrementing the other counter of said processor's counter pair that has become the current counter; referencing said shared data element; and decrementing whichever counter of said processor's counter pair remains incremented; updating said shared data element in a manner that preserves a pre-update version of said data element; switching said global counter selector to establish a new current counter of each per-processor counter pair; testing the non-current counter of each per-processor counter pair for zero; and destroying said shared data element's pre-update version upon the non-current counter of each per-processor counter pair being zero.