Vinzent Höfler schrieb:
On Tue, 28 Jun 2011 15:54:35 +0200, Michael Schnell <mschn...@lumino.de>
wrote:
But if you do the same with
volatile static int x;
the code will stay and another thread can watch x growing in a time
sharing system.
No, it can't. "volatile" just ensures that accessing the variable
results in
actual memory accesses. That does not mean cache-coherence, so another core
may still see other (as in "older") values.
I dare to disagree. When reading a volatile variable requires a memory
(RAM) read in one core, it will require the same read in any other core,
and updates have to occur in write-through into the RAM.
A difference could occur only, when the "memory" access may end up in
the cache instead of in RAM. Question is, what makes one variable use
read/write-through, while other variables can be read from the cache,
with lazy-write? Is this a compiler requirement, which has to enforce
read/write-through for all volatile variables? But if so, which
variables (class fields...) can ever be treated as non-volatile, when
they can be used from threads other than the main thread?
DoDi
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