1. A computer-implemented method, comprising: initiating execution of a thread on a processor in a transactional memory system; the thread attempting execution of a transaction; a hardware mechanism detecting an abort event for the transaction, wherein said detecting an abort event comprises detecting that the transaction has aborted or will abort; in response to said detecting, the hardware mechanism providing information about the detected abort event to a contention management mechanism wherein said providing comprises updating a value stored in a register on the processor on which the thread is attempting execution of the transaction whose value explicitly identifies a processor that caused an abort event with a value that identifies a processor that caused the detected abort event; and the contention management mechanism making a contention management decision dependent, at least in part, on the information about the detected abort event that is provided by the hardware mechanism, wherein said making a contention management decision comprises determining an action to be taken in response to the detected abort event, and wherein said determining an action comprises determining, dependent on the information about the detected abort event, whether to retry execution of the transaction using transactional lock elision or to attempt execution of the transaction using mutual exclusion.