This only avoided the ABA problem if the code which is ABA prone is run in-between the LL and SC instruction. But this is where the problem starts. E.g. for RI

This only avoided the ABA problem if the code which is ABA prone is run in-between the LL and SC instruction. But this is where the problem starts. E.g. for RISC when using LR/SC in a way which prevents ABA your are always losing all forward guarantees and it's totally valid for a implementation to be done in a way which will just never complete in such cases...