Nick Piggin wrote: > Stefan Richter wrote: >> Nick Piggin wrote: >> >>> I don't know why people would assume volatile of atomics. AFAIK, most >>> of the documentation is pretty clear that all the atomic stuff can be >>> reordered etc. except for those that modify and return a value. >> >> >> Which documentation is there? > > Documentation/atomic_ops.txt > > >> For driver authors, there is LDD3. It doesn't specifically cover >> effects of optimization on accesses to atomic_t. >> >> For architecture port authors, there is Documentation/atomic_ops.txt. >> Driver authors also can learn something from that document, as it >> indirectly documents the atomic_t and bitops APIs. >> > > "Semantics and Behavior of Atomic and Bitmask Operations" is > pretty direct :) > > Sure, it says that it's for arch maintainers, but there is no > reason why users can't make use of it. Note, LDD3 page 238 says: "It is worth noting that most of the other kernel primitives dealing with synchronization, such as spinlock and atomic_t operations, also function as memory barriers." I don't know about Linux 2.6.10 against which LDD3 was written, but currently only _some_ atomic_t operations function as memory barriers. Besides, judging from some posts in this thread, saying that atomic_t operations dealt with synchronization may not be entirely precise. -- Stefan Richter -=====-=-=== =--- =--=- http://arcgraph.de/sr/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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