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Hello, I have been reading up on atomics and struggle to grasp when exactly I need explicit memory barriers. While the documentation (Documentat/atomic_ops.txt), talks about operations needing explicit barriers both sides, I assume this is only half true. If I for instance only want to use an atomic as a flag to show that some operation is complete I reckon that a barrier before is sufficient. Furthermore I found the following lines: 288 If a caller requires memory barrier semantics around an atomic_t 289 operation which does not return a value, a set of interfaces are 290 defined which accomplish this: 291 292 void smp_mb__before_atomic(void); 293 void smp_mb__after_atomic(void);note how it refers to "operation which does not return a value", why can't I use these for atomic operations that do return a value? What should I use instead, normal barriers like mb? Please enlighten me Malte |
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