Abstract: Various embodiments of systems and methods for variable length data protected by Seqlock are described herein. Seqlock is a special locking mechanism used in data structures for multithreaded applications that can be read very quickly, when there are no changes being made, at the cost of needing to repeat a read operation when writing has occurred. A Seqlock, in normal use, can only protect a fixed-size data structure with no pointers. This is because the writing thread may invalidate a pointer after a reading thread has followed it. The embodiments specify an algorithm where a Seqlock-protected pointer, once written, is never invalidated. This removes the “no pointers” restriction, allowing the Seqlock to protect a simple singly-linked list, which can be safely increased in size while being read by other threads. The innovation includes the use of the write-once head and next pointers, and the always valid end iterator.

Abstract: Various embodiments of systems and methods for variable length data protected by Seqlock are described herein. Seqlock is a special locking mechanism used in data structures for multithreaded applications that can be read very quickly, when there are no changes being made, at the cost of needing to repeat a read operation when writing has occurred. A Seqlock, in normal use, can only protect a fixed-size data structure with no pointers. This is because the writing thread may invalidate a pointer after a reading thread has followed it. The embodiments specify an algorithm where a Seqlock-protected pointer, once written, is never invalidated. This removes the “no pointers” restriction, allowing the Seqlock to protect a simple singly-linked list, which can be safely increased in size while being read by other threads. The innovation includes the use of the write-once head and next pointers, and the always valid end iterator.