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Marco Elver authored
The definition of "conflict" should not include the type of access nor whether the accesses are concurrent or not, which this patch addresses. The definition of "data race" remains unchanged. The definition of "conflict" as we know it and is cited by various papers on memory consistency models appeared in [1]: "Two accesses to the same variable conflict if at least one is a write; two operations conflict if they execute conflicting accesses." The LKMM as well as the C11 memory model are adaptations of data-race-free, which are based on the work in [2]. Necessarily, we need both conflicting data operations (plain) and synchronization operations (marked). For example, C11's definition is based on [3], which defines a "data race" as: "Two memory operations conflict if they access the same memory location, and at least one of them is a store, atomic store, or atomic read-modify-write operation. In a sequentially consistent execution, two memory operations from different threads form a type 1 data race if they conflict, at least one of them is a data operation, and they are adjacent in <T (i.e., they may be executed concurrently)." [1] D. Shasha, M. Snir, "Efficient and Correct Execution of Parallel Programs that Share Memory", 1988. URL: http://snir.cs.illinois.edu/listed/J21.pdf [2] S. Adve, "Designing Memory Consistency Models for Shared-Memory Multiprocessors", 1993. URL: http://sadve.cs.illinois.edu/Publications/thesis.pdf [3] H.-J. Boehm, S. Adve, "Foundations of the C++ Concurrency Memory Model", 2008. URL: https://www.hpl.hp.com/techreports/2008/HPL-2008-56.pdfSigned-off-by: Marco Elver <elver@google.com> Co-developed-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Acked-by: Andrea Parri <parri.andrea@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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