Virgil Palanciuc wrote:
As I said, I have a global map that keeps the "tree roots"(as shared_ptr), and potentially many "walkers" that walk the tree. If two threads get the root from the global map - they'd get to read the very same shared_ptr variable; If two threads happen to walk the same node and try to get the "father" - they'd get to "lock" on the same weak_ptr variable simultaneously. Is that a problem?
No, it should work.
(assuming that I have "read locks" in place - i.e. there is currently no "writer" thread that is trying to completely remove a tree from the global map) [BTW - that's the only way that "writing" ever occurs: a "writer thread" builds an alternate version of a tree, and then acquires a write lock and replaces the old tree in the global map; there may be still walker threads that walk the "old tree" - but that should be ok since they keep a copy of the shared_ptr, basically guaranteeing that the old tree itself is not destroyed as long as there is a walker on it ]
Everything you describe sounds fine, at least in principle. There could be a bug in weak_ptr, a bug in your logic somewhere, or a bug in Snow Leopard's gcc (such things have happened in the past). If you suspect weak_ptr you could try to write a simple test that repeatedly locks the same instance from several threads and see if it cracks under the pressure.