Synchronizing exception control in a multiprocessor system using processing unit exception states and group exception states

A data processing apparatus comprising:

• a plurality of processing means for executing program instructions, each processing means executing a stream of program instructions corresponding to a processing thread;
• a plurality of groups comprising the plurality of processing means, wherein each processing means is in one of said plurality of groups;
• and
• exception control means for controlling exception processing of a group of said plurality of groups in response to an exception triggering event that corresponds with only said group out of said plurality of groups wherein said exception control means is configured to control each of said processing means within said group to respond to said exception triggering event by in sequence interrupting execution of said stream of program instructions associated with that processing means, executing a stream of exception handling program instructions to perform exception processing, and resuming execution of said stream of program instructions associated with that processing means,
• wherein for each processing means of said processing means within said group said exception control means is configured to control traversal only once for said exception triggering event of a sequence of processing means exception states,
• wherein said sequence of processing means exception states are in turn:
• (i) normal corresponding to processing of said stream of program instructions associated with that processing means;
• (ii) in-exception corresponding to processing of said exception handling program instructions;
• and
• (iii) done-exception corresponding to resumed processing of said stream of program instructions associated with that processing means;
• and
• wherein said exception control means is configured to move all of said processing means within said group from said done-exception state to said normal state upon starting of exception processing by all of said processing means within said group.

A method of processing data comprising the steps of:

• executing program instructions with a plurality of processing units, each processing unit executing a stream of program instructions corresponding to a processing thread, wherein a plurality of groups comprise the plurality of processing units and each processing unit is in one of said plurality of groups;
• controlling exception processing of a group of said plurality of groups in response to an exception triggering event that corresponds with only said group out of said plurality of groups;
• and
• controlling each processing unit of said processing units within said group to respond to said exception triggering event by in sequence interrupting execution of said stream of program instructions associated with that processing unit, executing a stream of exception handling program instructions to perform exception processing, and resuming execution of said stream of program instructions associated with that processing unit, wherein for each processing unit of said processing units within said group said step of controlling controls traversal only once for each exception triggering event of a sequence of processing unit exception states,
• wherein said sequence of processing unit exception states are in turn:
• (i) normal corresponding to processing of said stream of program instructions associated with that processing unit;
• (ii) in-exception corresponding to processing of said exception handling program instructions;
• and
• (iii) done-exception corresponding to resumed processing of said stream of program instructions associated with that processing unit;
• and
• wherein all of said processing units within said group are moved from said done-exception state to said normal state upon starting of exception processing by all of said processing units within said group.