Conditional transaction end instruction
A Conditional Transaction End (CTEND) instruction is provided that allows a program executing in a nonconstrained transactional execution mode to inspect a storage location that is modified by either another central processing unit or the Input/Output subsystem. Based on the inspected data, transactional execution may be ended or aborted, or the decision to end/abort may be delayed, e.g., until a predefined event occurs. For instance, when the instruction executes, the processor is in a nonconstrained transaction execution mode, and the transaction nesting depth is one at the beginning of the instruction, a second operand of the instruction is inspected, and based on the inspected data, transaction execution may be ended or aborted, or the decision to end/abort may be delayed, e.g., until a predefined event occurs, such as the value of the second operand becomes a prespecified value or a time interval is exceeded.
1. A computer program product for executing an instruction in a computing environment, said computer program product comprising:
a computer readable storage medium readable by a processing circuit and storing instructions for performing a method comprising:
obtaining the instruction for execution, the instruction having associated therewith an operation code to specify a conditional transaction end operation; and
executing, by a processor, the instruction, the executing comprising:
determining whether the processor is in a nonconstrained transactional execution mode;
determining whether a transaction nesting depth is of a predefined value;
based on the processor being in the nonconstrained transactional execution mode and the transaction nesting depth being of the predefined value, fetching an operand from a location specified by the instruction;
based on the operand comprising one value, ending a transaction associated with the instruction; and
based on the operand comprising another value, delaying completion of the instruction until a predefined action occurs.
2. The computer program product of claim 1 , wherein based on the operand comprising a further value, transactional execution of the transaction is aborted.
3. The computer program product of claim 2 , wherein the further value comprises a negative value, the one value comprises zero, and the other value comprises a positive value.
4. The computer program product of claim 2 , wherein based on aborting the transactional execution, a condition code in a transaction abort program status word is set to a defined value.
5. The computer program product of claim 1 , wherein the instruction includes one or more fields to provide the location from which the operand is fetched.
6. The computer program product of claim 5 , wherein the one or more fields comprise an index field, a base field, a first displacement field and a second displacement field, wherein contents of registers designated by one or more of the index field and the base field are added to a concatenation of the second displacement field and the first displacement field to provide the location.
7. The computer program product of claim 1 , wherein the operand is stored by another processor or an input/output subsystem coupled to the processor.
8. The computer program product of claim 1 , wherein the predefined action comprises exceeding an interval of time, and wherein the executing further comprises:
aborting transactional execution of the transaction; and
setting a condition code in a transaction abort program status word to a defined value.
9. The computer program product of claim 1 , wherein based on ending the transaction, store accesses made by the transaction are committed, a transaction nesting depth is set to zero, the processor exits transactional execution mode, and a condition code is set to a defined value.
10. A computer system for executing an instruction in a computing environment, said computer system comprising:
a memory; and
a processor in communication with the memory, wherein the computer system is configured to perform a method, said method comprising:
obtaining the instruction for execution, the instruction having associated therewith an operation code to specify a conditional transaction end operation; and
executing, by the processor, the instruction, the executing comprising:
determining whether the processor is in a nonconstrained transactional execution mode:
determining whether a transaction nesting depth is of a predefined value;
based on the processor being in the nonconstrained transactional execution mode and the transaction nesting depth being of the predefined value, fetching an operand from a location specified by the instruction;
based on the operand comprising one value, ending a transaction associated with the instruction; and
based on the operand comprising another value, delaying completion of the instruction until a predefined action occurs.
11. The computer system of claim 10 , wherein based on the operand comprising a further value, transactional execution of the transaction is aborted.
12. The computer system of claim 10 , wherein the predefined action comprises exceeding an interval of time, and wherein the executing further comprises:
aborting transactional execution of the transaction; and
setting a condition code in a transaction abort program status word to a defined value.
13. The computer system of claim 10 , wherein based on ending the transaction, store accesses made by the transaction are committed, a transaction nesting depth is set to zero, the processor exits transactional execution mode, and a condition code is set to a defined value.
14. A computer-implemented method of executing an instruction in a computing environment, said computer-implemented method comprising:
obtaining the instruction for execution, the instruction having associated therewith an operation code to specify a conditional transaction end operation; and
executing, by a processor, the instruction, the executing comprising:
determining whether the processor is in a nonconstrained transactional execution mode;
determining whether a transaction nesting depth is of a predefined. value;
based on the processor being in the nonconstrained transactional execution mode and the transaction nesting depth being of the predefined value, fetching an operand from a location specified by the instruction;
based on the operand comprising one value, ending a transaction associated with the instruction; and
based on the operand comprising another value, delaying completion of the instruction until a predefined action occurs.
15. The computer-implemented method of claim 14 , wherein based on the operand comprising a further value, transactional execution of the transaction is aborted.
16. The computer-implemented method of claim 14 , wherein the predefined action comprises exceeding an interval of time, and wherein the executing further comprises:
aborting transactional execution of the transaction; and
setting a condition code in a transaction abort program status word to a defined value.
17. The computer-implemented method of claim 14 , wherein based on ending the transaction, store accesses made by the transaction are committed, a transaction nesting depth is set to zero, the processor exits transactional execution mode, and a condition code is set to a defined value.
18. The computer-implemented method of claim 14 , wherein the instruction includes one or more fields to provide the location from which the operand is fetched.
19. The computer system of claim 10 , wherein the instruction includes one or more fields to provide the location from which the operand is fetched.
20. The computer system of claim 10 , wherein the operand is stored by another processor or an input/output subsystem coupled to the processor.