Prior Operation Subsequent Operation --------------- --------------------------- C Self R W RMW Self R W DR DW RMW SV -- ---- - - --- ---- - - -- -- --- -- Relaxed store Y Y Relaxed load Y Y Y Y Relaxed RMW operation Y Y Y Y rcu_dereference() Y Y Y Y Successful *_acquire() R Y Y Y Y Y Y Successful *_release() C Y Y Y W Y smp_rmb() Y R Y Y R smp_wmb() Y W Y Y W smp_mb() & synchronize_rcu() CP Y Y Y Y Y Y Y Y Successful full non-void RMW CP Y Y Y Y Y Y Y Y Y Y Y smp_mb__before_atomic() CP Y Y Y a a a a Y smp_mb__after_atomic() CP a a Y Y Y Y Y Y Key: Relaxed: A relaxed operation is either READ_ONCE(), WRITE_ONCE(), a *_relaxed() RMW operation, an unsuccessful RMW operation, a non-value-returning RMW operation such as atomic_inc(), or one of the atomic*_read() and atomic*_set() family of operations. C: Ordering is cumulative P: Ordering propagates R: Read, for example, READ_ONCE(), or read portion of RMW W: Write, for example, WRITE_ONCE(), or write portion of RMW Y: Provides ordering a: Provides ordering given intervening RMW atomic operation DR: Dependent read (address dependency) DW: Dependent write (address, data, or control dependency) RMW: Atomic read-modify-write operation SELF: Orders self, as opposed to accesses before and/or after SV: Orders later accesses to the same variable