Conditional access with timeout

• US 9,940,128 B2
• Filed: 10/06/2015
• Issued: 04/10/2018
• Est. Priority Date: 10/06/2015
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Steinmacher-Burow, Burkhard
• Primary Examiner(s): Padmanabhan, Mano
• Assistant Examiner(s): BORGES, PATRICK W
• Application Number:
  US14/875,829
• Publication Number:
  US 20170097779A1
• Time in Patent Office: 917 Days
• CPC Class Codes: G06F 12/00 Accessing, addressing or allocating within memory systems or architectures digital input from, or digital output to record carriers, e.g. to disk storage units, G06F3/06
• CPC Class Codes: G06F 12/0897 with two or more cache hierarchy levels with multilevel cache hierarchies G06F12/0811
• CPC Class Codes: G06F 9/30 Arrangements for executing machine instructions, e.g. instruction decode for executing microinstructions G06F9/22
• CPC Class Codes: G06F 9/3004 to perform operations on memory
• CPC Class Codes: G06F 9/30043 LOAD or STORE instructions; Clear instruction
• CPC Class Codes: G06F 9/30072 to perform conditional operations, e.g. using predicates or guards
• CPC Class Codes: G06F 9/30087 Synchronisation or serialisation instructions
• CPC Class Codes: G06F 9/46 Multiprogramming arrangements

Abstract

A method can include receiving a first memory load request by a conditional load with time out (CLT) device at a first time. The first memory load request can specify a first condition. A first determination of whether the first condition is satisfied is performed. The CLT device determines a wait period when the first condition is not satisfied. A reply is issued. The reply indicates that the first condition is satisfied when the first condition is satisfied. The reply indicates that the first condition is not satisfied when the duration of the wait period exceeds a time-out threshold. When the first condition is not satisfied, a first memory store request can be received during the wait period and a second determination of whether the first condition satisfied performed. The reply indicates that the first condition is satisfied when the second determination is that the first condition is satisfied.

Claims

1. A method for responding to memory requests, comprising:

receiving a first memory load request by a conditional load with time out (CLT) device at a first time, the first memory load request specifying a first condition and a first memory address;

performing a first determination of whether the first condition is satisfied;

starting a timer at the CLT device to determine a wait period when the first condition is not satisfied;

responding to the first memory load request with a reply, wherein the reply indicates that the first condition is not satisfied when the duration of the wait period exceeds a time-out threshold; and

when the first condition is not satisfied;

receiving a first memory store request by the CLT device at a second time subsequent to the first time and prior to the wait period exceeding the time-out threshold, the first memory store request specifying the first memory address and a value;

storing the value at the first memory address;

performing a second determination of whether the first condition is satisfied; and

responding to the first memory load request with a reply, wherein the reply indicates that the first condition is satisfied when the second determination is that the first condition is satisfied.

2. The method of claim 1, wherein the value specified by the first memory store request is used in the second determination of whether the first condition is satisfied.

3. The method of claim 1, wherein the reply indicating that the first condition is satisfied when the second determination is that the first condition is satisfied includes the value specified by the first memory store request.

4. The method of claim 1, wherein the reply indicates that the first condition is satisfied when the first condition is satisfied.

5. The method of claim 1, wherein the reply includes a value at the first memory address.

6. The method of claim 1, wherein a value at the first memory address is used in the first determination of whether the first condition is satisfied.

7. The method of claim 1, wherein the first memory load request includes an operand and the operand is used in the first determination of whether the first condition is satisfied.

8. The method of claim 1, wherein a first value at the first memory address and a second value at a second memory address are used in the first determination of whether the first condition is satisfied.

9. A conditional load with time out (CLT) device for responding to memory requests, comprising:

a timer;

a memory to store a pending memory load request; and

a logic circuit to;

receive a first memory load request at a first time, the first memory load request specifying a first condition and a first memory address;

perform a first determination of whether the first condition is satisfied;

start a timer to determine a wait period when the first condition is not satisfied;

respond to the first memory load request with a reply, wherein the reply indicates that the first condition is not satisfied when the duration of the wait period exceeds a time-out threshold; and

when the first condition is not satisfied;

receive a first memory store request at a second time subsequent to the first time and prior to the wait period exceeding the time-out threshold, the first memory store request specifying the first memory address and a value;

store the value at the first memory address;

perform a second determination of whether the first condition is satisfied; and

respond to the first memory load request with a reply, wherein the reply indicates that the first condition is satisfied when the second determination is that the first condition is satisfied.

10. The CLT device of claim 9, wherein the value specified by the first memory store request is used in the second determination of whether the first condition is satisfied.

11. The CLT device of claim 9, wherein the reply indicates that the first condition is satisfied when the first condition is satisfied.

12. The CLT device of claim 9, wherein the reply includes a value at the first memory address.

13. The CLT device of claim 9, wherein a value at the first memory address is used in the first determination of whether the first condition is satisfied.

14. The CLT device of claim 9, wherein the first memory load request includes an operand and the operand is used in the first determination of whether the first condition is satisfied.

15. A computer program product for responding to memory requests, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, wherein the computer readable storage medium is not a transitory signal per se, the program instructions executable by a conditional load with time out (CLT) device to cause the CLT device to perform a method comprising:

receiving a first memory load request by the CLT device at a first time, the first memory load request specifying a first condition and a first memory address;

performing a first determination of whether the first condition is satisfied;

starting a timer at the CLT device to determine a wait period when the first condition is not satisfied;

responding to the first memory load request with a reply, wherein the reply indicates that the first condition is not satisfied when the duration of the wait period exceeds a time-out threshold; and

when the first condition is not satisfied;

receiving a first memory store request by the CLT device at a second time subsequent to the first time and prior to the wait period exceeding the time-out threshold, the first memory store request specifying the first memory address and a value;

storing the value at the first memory address;

performing a second determination of whether the first condition is satisfied; and

responding to the first memory load request with a reply, wherein the reply indicates that the first condition is satisfied when the second determination is that the first condition is satisfied.

16. The computer program product of claim 15, wherein the reply indicates that the first condition is satisfied when the first condition is satisfied.

17. The computer program product of claim 15, wherein a value at the first memory address is used in the first determination of whether the first condition is satisfied.