Covered every arm of the SMP thread stack check with a new test

2026-09-19T19:03:03Z

TX_THREAD_STACK_CHECK sits on nine sites in the SMP scheduler and scores seven conditions at each of them. Ordinary use only ever takes the clean arm of five of those, so the nine sites sat between eight and eleven of fourteen -- 44 uncovered branch outcomes. A new test applies one fault to every thread the sites look at, drives one site with it in place, and takes it out again: the lowest recorded stack pointer put above the thread's own, each of the two fences around the stack overwritten, the recorded pointer dropped below the stack, the word under it made used, and the thread identifier cleared. The fault is applied per step rather than per pass, because the first site to see a bad recorded pointer repairs it on the way through. Three sites look at the thread the core is about to run rather than the one being operated on, and only a time-slice rotation separates the two, so those steps rotate the ready list and hold preemption off across the rotation and the service that follows it -- except the preemption check, which does nothing while preemption is held off. A cleared identifier is incompatible with the published entry points, so the steps drive the internal ones. The file also covers the two parts of the stack machinery no fault reaches: the realignment a create performs when it is handed an odd stack address, and the error handler's MISRA build, where there is no application handler to call and the function exists only to keep its argument referenced. 36 of the 44 outcomes close, with one branch and one line in tx_thread_create.c and two branches and three lines in tx_thread_stack_error_handler.c. The eight left are the macro's own null-thread arm. Four of the nine sites guard it in the source with a null test of their own, so it cannot be taken there at all; four more are handed a thread the caller has already dereferenced; the ninth, in tx_thread_relinquish, already takes it. 113/113 tests in each of eight build configurations, from clean, with retries disabled. Assisted-by: Claude Code (Opus 5)

threadx.git/test/smp/regression/threadx_thread_stack_check_test.c, branch v6.4.1_cert

Covered every arm of the SMP thread stack check with a new test