1. A method, comprising: using a computer to perform: determining whether an indication of ownership for a portion of a shared memory specifies that attempts to modify the portion of the shared memory should be made in a non-transactional software-mode or specifies that attempts to modify the portion of the shared memory should be made in a transactional-mode, wherein the portion of the shared memory stores the current contents of a shared data structure; and subsequent to said determining: selecting between using a transaction and using software operations for attempting to modify the portion of the shared memory, wherein selecting between using a transaction and using software operations is dependent on whether the indication of ownership specifies that attempts to modify the portion of the shared memory should be made in the transactional-mode or specifies that attempts to modify the portion of the shared memory should be made in the non-transactional software-mode; and attempting to modify a value of the portion of the shared memory using a transaction or using software operations, dependent on said selecting.