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
<http://users.sosdg.org/%7Eqiyong/lxr/source/Documentation/atomic_ops.txt#L288>
If a caller requires memory barrier semantics around an atomic_t
289
<http://users.sosdg.org/%7Eqiyong/lxr/source/Documentation/atomic_ops.txt#L289>
operation which does not return a value, a set of interfaces are
290
<http://users.sosdg.org/%7Eqiyong/lxr/source/Documentation/atomic_ops.txt#L290>
defined which accomplish this:
291 <http://users.sosdg.org/%7Eqiyong/lxr/source/Documentation/atomic_ops.txt#L291>
292 <http://users.sosdg.org/%7Eqiyong/lxr/source/Documentation/atomic_ops.txt#L292> void smp_mb__before_atomic(void);
293
<http://users.sosdg.org/%7Eqiyong/lxr/source/Documentation/atomic_ops.txt#L293>
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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