Messages in this thread | | | From | Segher Boessenkool <> | Subject | Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures | Date | Tue, 11 Sep 2007 04:27:22 +0200 |
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>> "volatile" has nothing to do with reordering. atomic_dec() writes >> to memory, so it _does_ have "volatile semantics", implicitly, as >> long as the compiler cannot optimise the atomic variable away >> completely -- any store counts as a side effect. > > Stores can be reordered. Only x86 has (mostly) implicit write ordering. > So no atomic_dec has no volatile semantics
Read again: I said the C "volatile" construct has nothing to do with CPU memory access reordering.
> and may be reordered on a variety > of processors. Writes to memory may not follow code order on several > processors.
The _compiler_ isn't allowed to reorder things here. Yes, of course you do need stronger barriers for many purposes, volatile isn't all that useful you know.
Segher
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