Alexander Terekhov wrote:
< 2 x Forward Inline >
[snip]
There's no COW semantics here. It's rather simple, really. Any
operation that "updates" the use-count needs to be synchronized
with respect to other readers/writers. The basic thread safety
is pretty much the same stuff as POSIX's memory synchronization
rules stated in 4.10/Base Definitions volume. Note that things
like semas and pthread_refcount_t provide STRONG thread-safety
(for themselves; from "OO" point of view, if you look at their
interface); well, with some "exceptions"... please take a look
at pthread_refcount_setvalue().
I'm a newbie, so this might seem a simple question: Wouldn't
weighted reference counts eliminate around half the synchronization.
This is because, AFAICT, the only time synchronization is needed is
when a smart weighted pointer releases it's pointee, but not
when it acquires a new pointee (because the reference count is
gotten from the other, or source, smart weighted pointer).
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