1 Prior Operation Subsequent Operation 2 --------------- --------------------------- 3 C Self R W RMW Self R W DR DW RMW SV 4 -- ---- - - --- ---- - - -- -- --- -- 5 6 Relaxed store Y Y 7 Relaxed load Y Y Y Y 8 Relaxed RMW operation Y Y Y Y 9 rcu_dereference() Y Y Y Y 10 Successful *_acquire() R Y Y Y Y Y Y 11 Successful *_release() C Y Y Y W Y 12 smp_rmb() Y R Y Y R 13 smp_wmb() Y W Y Y W 14 smp_mb() & synchronize_rcu() CP Y Y Y Y Y Y Y Y 15 Successful full non-void RMW CP Y Y Y Y Y Y Y Y Y Y Y 16 smp_mb__before_atomic() CP Y Y Y a a a a Y 17 smp_mb__after_atomic() CP a a Y Y Y Y Y Y 18 19 20 Key: Relaxed: A relaxed operation is either READ_ONCE(), WRITE_ONCE(), 21 a *_relaxed() RMW operation, an unsuccessful RMW 22 operation, a non-value-returning RMW operation such 23 as atomic_inc(), or one of the atomic*_read() and 24 atomic*_set() family of operations. 25 C: Ordering is cumulative 26 P: Ordering propagates 27 R: Read, for example, READ_ONCE(), or read portion of RMW 28 W: Write, for example, WRITE_ONCE(), or write portion of RMW 29 Y: Provides ordering 30 a: Provides ordering given intervening RMW atomic operation 31 DR: Dependent read (address dependency) 32 DW: Dependent write (address, data, or control dependency) 33 RMW: Atomic read-modify-write operation 34 SELF: Orders self, as opposed to accesses before and/or after 35 SV: Orders later accesses to the same variable
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