Thanks a lot
pon., 24 paź 2022, 05:09 użytkownik Peter Veentjer <[email protected]>
napisał:
> The program isn't clear to me. I guess you want something like this:
>
> int x;
> volatile int v;
>
> CPU1:
> write(x, 1) (1)
> write(v, 1) (2)
>
> CPU2
> read(v) (3)
> read(x) (4)
>
> Then there exists an execution where (4) sees value written by (1) it is
> in a data race with. E.g. (1)->(3)->(4).
>
> So since the program has at least 1 execution with a data race. So your
> observation that the program is not data race free, is correct.
>
> To resolve the data race, you want to do something like this:
>
> int x;
> volatile int v;
>
> CPU1:
> write(x, 1) (1)
> write(v, 1) (2)
>
> CPU2
> if(read(v)==1){ (3)
> print(read(x)); (4)
> }
>
> When (3) has observed the value written by (2) there is a happens-before
> edge between (2) and (3). And due to the program order between (1)/(2) and
> (3)/(4) and the transitive nature of happens-before, there is a
> happens-before edge between (1) and (4). So the value'1' should be printed.
>
> This program is data race free.
>
>
>
>
> On Sun, Oct 23, 2022 at 7:59 PM r r <[email protected]> wrote:
>
>> int x;
>> volatile int v;
>>
>> write(x, 1) read(v)
>> write(v, 1) read(x)
>>
>> Is that program data race free? On my eye it is not not because there is
>> an execution that write(x, 1) and read(x) are not in happens-before
>> relationship.
>>
>> --
>> You received this message because you are subscribed to the Google Groups
>> "mechanical-sympathy" group.
>> To unsubscribe from this group and stop receiving emails from it, send an
>> email to [email protected].
>> To view this discussion on the web, visit
>> https://groups.google.com/d/msgid/mechanical-sympathy/9a25a145-5271-4f7a-ad3d-3633367becd4n%40googlegroups.com
>> <https://groups.google.com/d/msgid/mechanical-sympathy/9a25a145-5271-4f7a-ad3d-3633367becd4n%40googlegroups.com?utm_medium=email&utm_source=footer>
>> .
>>
> --
> You received this message because you are subscribed to the Google Groups
> "mechanical-sympathy" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to [email protected].
> To view this discussion on the web, visit
> https://groups.google.com/d/msgid/mechanical-sympathy/CAGuAWdCCq8bLneYkLR%3D4Ddbjfk1dsJ8RrGx%3DyPgssPvzYKuQiw%40mail.gmail.com
> <https://groups.google.com/d/msgid/mechanical-sympathy/CAGuAWdCCq8bLneYkLR%3D4Ddbjfk1dsJ8RrGx%3DyPgssPvzYKuQiw%40mail.gmail.com?utm_medium=email&utm_source=footer>
> .
>
--
You received this message because you are subscribed to the Google Groups
"mechanical-sympathy" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion on the web, visit
https://groups.google.com/d/msgid/mechanical-sympathy/CAFKLJkwdYbY6PshKFd%3DHCv9OA2WA4gxXZxOv9N0GtUwutsKb%3DQ%40mail.gmail.com.
