Indicating a low priority transaction

1. A method for accessing at least one memory location by one of a plurality of transactions in a multi-processor transactional execution environment, the method comprising:

assigning, by a local processor, a conflict priority to a local transaction wherein the conflict priority is set by a conflict priority setting instruction;

receiving, by the local processor executing the local transaction, a protocol request packet from a remote processor executing a remote transaction, wherein the protocol request packet includes a request for a cache line of data from the local processor and a conflict priority of the remote transaction;

based on encountering a conflict with the remote transaction for a memory location, comparing, by the local processor, the assigned conflict priority of the local transaction with the conflict priority of the remote transaction; and

based on the conflict priority of the local transaction being a higher priority, the local processor continuing the local transaction, sending a protocol response packet rejecting the request, and the remote processor aborting the remote transaction; and

based on the conflict priority of the local transaction being a lower priority, aborting, by the local processor, the local transaction, and sending a protocol response packet including the requested cache line of data.

2. The method according to claim 1 , wherein a process includes one or more transactions and wherein the one or more transactions include one or more of a legacy transaction, a constrained transaction, and a nested transaction.

3. The method according to claim 2 , wherein a legacy transaction is assigned a default conflict priority.

4. The method according to claim 1 , wherein the assigning the conflict priority further comprises:

executing, by the local processor, the conflict priority setting instruction comprising a mnemonic field having a mnemonic value, and an operand corresponding to the conflict priority; and

immediately starting the local transaction with the assigned conflict priority.

5. The method according to claim 1 , wherein the protocol request packet comprises: a keyword; the conflict priority of the remote transaction; a tag field; an indicator corresponding to an access type; a target field identifying a storage location; and a cyclic redundancy check (CRC) field.

6. The method of claim 1 , wherein a non-transactional memory access is assigned a conflict priority including either the default conflict priority or a conflict priority specified by a thread.

7. A computer program product for accessing at least one memory location by one of a plurality of transactions in a multi-processor transactional execution environment, the computer program product comprising:

a computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising:

assigning, by a local processor, a conflict priority to a local transaction wherein the conflict priority is set by a conflict priority setting instruction;

receiving, by the local processor executing the local transaction, a protocol request packet from a remote processor executing a remote transaction, wherein the protocol request packet includes a request for a cache line of data from the local processor and a conflict priority of the remote transaction;

based on encountering a conflict with the remote transaction for a memory location, comparing, by the local processor, the assigned conflict priority of the local transaction with the conflict priority of the remote transaction;

based on the conflict priority of the local transaction being a higher priority, the local processor continuing the local transaction, sending a protocol response packet rejecting the request, and the remote processor aborting the remote transaction; and

based on the conflict priority of the local transaction being a lower priority, aborting, by the local processor, the local transaction, and sending a protocol response packet including the requested cache line of data.

8. The computer program product according to claim 7 , wherein a process includes one or more transactions and wherein the one or more transactions include one or more of a legacy transaction, a constrained transaction, and a nested transaction.

9. The computer program product according to claim 8 , wherein a legacy transaction is assigned a default conflict priority.

10. The computer program product according to claim 7 , wherein the assigning the conflict priority further comprises:

executing, by the local processor, the conflict priority setting instruction comprising a mnemonic field having a mnemonic value, and an operand corresponding to the conflict priority; and

immediately starting the local transaction with the assigned conflict priority.

11. The computer program product according to claim 7 , wherein the protocol request packet comprises: a keyword; the conflict priority of the remote transaction; a tag field; an indicator corresponding to an access type; a target field identifying a storage location; and a cyclic redundancy check (CRC) field.

12. The computer program product according to claim 7 , wherein the conflict priority further comprises at least one of:

a continuous range of values;

a Boolean value;

an integer value;

a floating point value;

a decimal value;

a hexadecimal value; and

a binary value.

13. The computer program product of claim 7 , wherein a non-transactional memory access is assigned a conflict priority including either the default conflict priority or a conflict priority specified by a thread.

14. A computer system for accessing at least one memory location by one of a plurality of transactions in a multi-processor transactional execution environment, the computer system comprising:

a memory; and

a processor in communications with the memory, wherein the computer system is configured to perform a method, said method comprising:

assigning, by a local processor, a conflict priority to a local transaction wherein the conflict priority is set by a conflict priority setting instruction;

receiving, by the local processor executing the local transaction, a protocol request packet from a remote processor executing a remote transaction, wherein the protocol request packet includes a request for a cache line of data from the local processor and a conflict priority of the remote transaction;

based on encountering a conflict with the remote transaction for a memory location, comparing, by the local processor, the assigned conflict priority of the local transaction with the conflict priority of the remote transaction; and

based on the conflict priority of the local transaction being a higher priority, the local processor continuing the local transaction, sending a protocol response packet rejecting the request, and the remote processor aborting the remote transaction; and

based on the conflict priority of the local transaction being a lower priority, aborting, by the local processor, the local transaction, and sending a protocol response packet including the requested cache line of data.

15. The computer system according to claim 14 , wherein a process includes one or more transactions and wherein the one or more transactions include one or more of a legacy transaction, a constrained transaction, and a nested transaction.

16. The computer system according to claim 15 , wherein a legacy transaction is assigned a default conflict priority.

17. The computer system of claim 14 , wherein a non-transactional memory access is assigned a conflict priority including either the default conflict priority or a conflict priority specified by a thread.

18. The computer system according to claim 14 , wherein the protocol request packet comprises: a keyword; the conflict priority of the remote transaction; a tag field; an indicator corresponding to an access type; a target field identifying a storage location; and a cyclic redundancy check (CRC) field.

19. The computer system according to claim 14 , wherein the assigning the conflict priority further comprises:

executing, by the local processor, the conflict priority setting instruction comprising a mnemonic field having a mnemonic value, and an operand corresponding to the conflict priority; and

immediately starting the local transaction with the assigned conflict priority.

20. The computer system according to claim 19 , wherein the operand further comprises at least one of:

a control register;

a special purpose register;

a general purpose register;

a location calculated as an offset from a base address;

a floating point register; and

an immediate parameter.