Scheduling of duplicate threads

A non-transitory computer readable storage medium having stored thereon a computer readable dataset description that, when processed in an integrated circuit manufacturing system, causes the integrated circuit manufacturing system to manufacture an integrated circuit embodying a processing system comprising:

• a plurality of parallel execution units each operable to execute a respective series of threads, wherein at least some of the threads executed by at least some of the execution units are non-critical threads not being designated as critical;
• request buffering storage operable to receive a request indicating that one of the threads in the respective series executed by a first one of the execution units is designated as a critical thread;
• safety thread scheduling circuitry arranged to read the request from the request buffering storage, and in response to schedule a check thread, being a duplicate of the critical thread, to be executed on a second one of the plurality of execution units other than the first execution unit;
• result buffering storage arranged to buffer one of:
• a first result being a result of the execution of the critical thread on the first execution unit, and a second result being a result of the execution of the check thread on the second execution unit;
• and
• comparison circuitry arranged to compare said one of the first and second results from the result buffering storage with the other of the first and second results, and to raise error signal if the first and second results do not match according to said comparison;
• wherein the request includes an indication of a safety time-window;
• and
• wherein the safety thread scheduling circuitry is configured to detect when at least one of the execution units is idle, and if none of the execution units is detected to be idle by the expiry of the safety time-window, to interrupt one of the non-critical threads executing on a non-idle one of the execution units and select the non-idle execution unit as the second execution unit to execute the check thread in place of the interrupted thread.

A method comprising:

• scheduling a respective series of threads to execute on each of a plurality of parallel execution units, wherein at least some of the threads executed by at least some of the execution units are non-critical threads not being designated as critical;
• receiving a request indicating that one of the threads in the respective series executed by a first one of the execution units is designated as a critical thread;
• scheduling a check thread in response to the request, the check thread being a duplicate of the critical thread, to be executed on a second one of the plurality of execution units other than the first execution unit;
• buffering one of:
• a first result being a result of the execution of the critical thread on the first execution unit, and a second result being a result of the execution of the check thread on the second execution unit;
• comparing a first result with a second result, the first result being a result of the execution of the critical thread on the first execution unit, and the second result being a result of the execution of the check thread on the second execution unit;
• and
• detecting whether the first and second results match according to said comparison;
• wherein the request includes an indication of a safety time-window;
• and
• wherein the method further comprises detecting when at least one of the execution units is idle, and upon none of the execution units being detected to be idle by the expiry of the safety time-window, interrupting one of the non-critical threads executing on a non-idle one of the execution units and select the non-idle execution unit as the second execution unit to execute the check thread in place of the interrupted thread.