Szabolcs Ferenczi <szabolcs.ferenczi@[EMAIL PROTECTED]
> writes:
> On May 2, 12:43 pm, Anthony Williams <anthony_w....@[EMAIL PROTECTED]
> wrote:
>> [...]
>> All accesses to shared data MUST be synchronized with atomics: [...]
>
> Can you elaborate this point please. How can you generally synchronise
> N processes with help of atomics? Do you mean only two processes under
> certain circumstances?
If any thread modifies shared data that is not of type atomic_xxx, the
developer must ensure appropriate synchronization with any other thread
that
accesses that shared data in order to avoid a data race (and the undefined
behaviour that comes with that). If you're using atomics, that means you
must
have (at least) a release on some atomic variable by the modifying thread
after the modify, and an acquire on the same atomic variable by the other
thread before its access (read or write).
If you have N threads accessing the shared data, and one does a modify,
all
the other N-1 threads must be properly synchronized with the modifying
thread
as above in order to avoid data races.
Of course, you could also just use a mutex lock or join with the thread
doing
the modification.
Anthony
--
Anthony Williams | Just Software Solutions Ltd
Custom Software Development | http://www.justsoftwaresolutions.co.uk
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