Thread suspension system and method using trapping instructions in delay slots

A computer program product encoded in computer readable media, said computer program product comprising:

• mutator code executable on a computer as a mutator process having a thread with a safe point defined therein;
• an instance of a delayed control transfer instruction, wherein said delayed control transfer instruction instance coincides with said safe point;
• and
• an instance of an instruction encoded in a delay slot of said delayed control transfer instruction instance, said delay slot instruction instance referencing storage encodable with an exception triggering value to trigger an exception for suspending said thread at said safe point.

A computer-implemented method of providing mutator code with support for suspension of at least one execution thread thereof at a safe point, said method comprising:

• encoding an instance of a delayed control transfer instruction in an execution sequence of instructions of said mutator code;
• encoding information accessible to a collector process to identify at least a portion of a root set of storage locations at a safe point in said execution sequence of instructions coinciding with said delayed control transfer instruction instance;
• and
• encoding in a delay slot of said delayed control transfer instruction instance an instruction instance referencing storage encodable with an exception triggering value to trigger an exception for suspending execution of said mutator code at said safe point.

A method of coordinating garbage collection with execution of a multi-threaded mutator, wherein said garbage collection is performed at safe points in an execution trajectory of said multi-threaded mutator, and wherein potentially inconsistent threads of said multi-threaded mutator are suspended at said safe points to facilitate said garbage collection, said method comprising:

• upon a start garbage collection event, encoding an exception triggering value in storage referenced by exception triggering instructions in delay slots of delayed control transfer instructions coinciding with said safe points;
• thereafter, upon execution of said exception triggering instructions, suspending the corresponding one of said threads;
• and
• performing said garbage collection after each of said threads is suspended.

An apparatus comprising:

• a processor having a storage location accessible to plural execution threads thereon and having an instruction set including an exception triggering instruction and a delayed control transfer instruction;
• media readable by said processor for encoding mutator code including an instance of said delayed control transfer instruction with an instance of said exception triggering instruction in a delay slot thereof, said exception triggering instruction instance referencing said storage location;
• thread suspension means responsive to a start garbage collection event to encode said storage location with an exception triggering value;
• and
• handler means responsive to execution of said exception triggering instruction when said storage location encodes said an exception triggering value.