On May 2, 2:35 am, "Boehm, Hans" <hans.bo...@hp.com> wrote:
On May 1, 2:26 pm, Szabolcs Ferenczi <szabolcs.feren...@gmail.com>
wrote:> On Apr 28, 8:42 pm, "Boehm, Hans" <hans.bo...@hp.com> wrote:
On Apr 21, 10:07 am, Szabolcs Ferenczi <szabolcs.feren...@gmail.com>
wrote:
[...]
In
particular, it I write the equivalent of
Thread 1:
x = 42;
x_init = true;
Thread 2:
while (!x_init);
assert(x == 42);
this can fail (and in fact is incorrect) even if x_init is atomic.
Of course it is incorrect. Here both `x' and `x_init' are shared
variables but you miss to declare them as such. Furthermore, you are
trying to access them `in sequential manner' i.e. as if they were
variables in a sequential program. However, then, why are you
wondering that an incorrect concurrent program can fail?
This is correct in Java and the C++0x working paper if x_init is
volatile(Java)/atomic(C++). The variable x cannot be simultaneously
accessed, hence there is no data race on x. And x_init is effectively
declared shared.
First of all, can you please decide which statement of yours is what
you really hold:
1) `this can fail (and in fact is incorrect) even if x_init is
atomic.'
2) `This is correct in Java and the C++0x working paper if x_init is
volatile(Java)/atomic(C++).'
Both statements are made by you and both refer to the same code
fragment. The only difference is that the first statement is made by
you for your original code fragment and the second one is made in
response to my comments.
What do you really think about it? Is it correct or incorrect?
parts of the original message. If you had you would see that the 'this