Multiprocessor system with cache-based software breakpoints

Techniques are disclosed for implementing software breakpoints in a multiprocessor system having a number of processors each coupled to a main memory. In an illustrative embodiment, each of the processors has an instruction cache associated therewith. An instruction for which a breakpoint is to be inserted is retrieved from a corresponding instruction address in the main memory, and a breakpoint code is inserted at the instruction address in main memory. After the breakpoint code is executed by a given one of the processors, the retrieved instruction is stored in the corresponding instruction cache for that processor, and a use-once indicator is set. The use-once indicator is operative via cache control logic to clear a validity indicator associated with the instruction after a single fetch of the instruction from the instruction cache, such that subsequent attempts by the given processor to access the instruction as stored in the instruction cache will cause the processor to retrieve the breakpoint code at the instruction address in main memory.