Alexander Terekhov wrote:
[...]
> Pavel Vasiliev wrote:
>> I place here the corrected version of my previous code.
> Well,
> Given: two threads -- A and B,
> thread A has "strong" one,
> thread B has "weak" one,
> strong_count == 1, weak_count == 2.
> Thread A, in release_strong:
> atomic_decrement(&strong_count) == 0,
> Thread B, in acquire_strong_from_weak:
> lock,
> see atomic_increment(&strong_count) > 0,
> (strong_count == 1, weak_count == 2)
> return true (and unlock),
> ...
> enter release_strong()
> atomic_decrement(&strong_count) == 0,
> enter strong_refs_lost(),
> see strong_count == 0,
> set strong_count < 0,
> unlock,
> destroy,
> enter release_weak(),
> atomic_decrement(&weak_count) == 1,
> (strong_count < 0, weak_count == 1)
> ...
> enter release_weak(),
> atomic_decrement(&weak_count) == 0,
> destruct_self()
> Thread A, enter strong_refs_lost():
Yeah... This attempt failed :-(. Thanks for preventing me from getting
into troubles!
However,
> WHA.. Nah, Lukashenko retires and establishes peace and democracy in
> the Middle East. ``Not bad.'' ;-)
I'd better leave my code as is. Or even dereference a NULL-pointer :-).
[...]
> pthread_refcount_decrement() // with msync for proper mut.obj-cleanup
> pthread_refcount_decrement_nomsync() // without any msync whatsoever
"nomsync" here stands for "no memory view update even when counter drops
to 0"? If yes, then you probably should not use it in
> void release_weak() {
> int status = pthread_refcount_decrement_no_msync(&weak_count);
> if (PTHREAD_REFCOUNT_DROPPED_TO_ZERO == status)
> destruct_self();
> }
Consider the following:
> Given: two threads -- A and B,
> thread A has "strong" one,
> thread B has "weak" one,
> strong_count == 1, weak_count == 2.
Thread A releases the last "strong" reference.
destruct_object() deletes p_object AND modifies the refs instance
(e.g. sets p_object to NULL for debug reasons).
strong_count == 0, weak_count == 1
Thread B releases the last "weak" reference.
release_weak() calls destruct_self() on expired memory view.
"Or am I just missing and/or misunderstanding something?" :-)
Pavel
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