On 13 May 2013 12:48, David Gibson <da...@gibson.dropbear.id.au> wrote: > On Mon, May 13, 2013 at 12:10:10PM +0100, Peter Maydell wrote: >> Hmm, is this the ideal semantics? Typically the owner of the >> MemoryListener isn't the owner of the AddressSpace so it isn't >> necessarily in a position to guarantee that it can unregister >> the listener before the address space is destroyed. In fact >> as the listener API is currently documented, the filter >> argument is just an optimisation to save the callbacks having >> to filter out irrelevant information themselves. > > If so, then it's broken by design. There's no guarantee that after an > AddressSpace is destroyed another one won't be created at the same > address (in fact, depending on your malloc() implementation, it could > be very likely). So references by pointer to an object *must* be > removed before the object itself is freed.
Mmm. Looking through the code it turns out we don't actually make use of the ability to pass NULL as a filter (except in target-arm/kvm.c which was just me being lazy and not passing in the system address space). Perhaps we should just drop that capability, at which point you have a clearer "you are listening on one AS and you must make sure you arrange to unregister before that AS goes away" API definition? -- PMM
