Mark H Weaver <m...@netris.org> skribis: > I forgot to mention an important aspect of the proposed auto-load > locking here. It would not be a global lock, but rather a lock specific > to the module being loaded. So, I guess we would need a global table of > locks for modules-being-loaded.
Right (we can’t add a mutex to the module record without breaking the ABI.) > Since Guile (unfortunately) allows cyclic module dependencies, we would > need a mechanism to avoid deadlocks in case modules A and B both import > each other, and two threads concurrently attempt to load those modules. > > The first idea that comes to mind is to also have a global structure > storing a partial order on the modules currently being loaded. If, > while module A is being loaded, there's an attempt to auto-load module > B, then an entry (A < B) would added to the partial order. The partial > order would not allow cycles to be introduced, reporting an error in > that case. In case a cycle would be introduced when adding (A < B), > then the thread would simply be given access to the partially-loaded > module B, by adding B to its local list of modules-being-loaded. Would it enough to (1) use recursive mutexes, and (2) have ‘resolve-module’ lookup modules first in the global name space, and second in the local list of modules being loaded? Thanks, Ludo’.
