Changelog

Version History

Software Version History

Software Version	Revision	Date	Notes
1.2.1	4	Oct 10, 2026	Changed: QRT_CFG_SCHED_TIME_SLICE_MIN_US, the shortest round-robin time slice, is required in qrt_cfg.h; pthread_attr_settimeslice_np() and pthread_create() reject shorter slices a preempted thread resumes before the ready threads of its priority and finishes its round-robin time slice; pthread_setschedparam() at an unchanged priority yields to equal-priority ready threads a {0, 0} absolute time is an ordinary past deadline: timed waits return ETIMEDOUT instead of EAGAIN or EBUSY; an absolute time before the epoch has passed instead of reporting EINVAL qrt_kernel_boot() and qrt_systimer_configure() return EBUSY once the kernel is running the resources of a detached thread are released one scheduling pass after it exits MPU builds: EPERM for unprivileged callers that would have the kernel run their code privileged
			Fixed: a priority change after an earlier lowering takes effect and is reported by pthread_getschedparam() a mutex owner boosted by priority inheritance returns to its own priority on unlock, also after nested boosts, and the unlock yields to a higher-priority ready thread pthread_setschedprio() and pthread_setschedparam() at a thread’s own priority keep an active priority-inheritance boost a thread releasing its last mutex a second time keeps its priority instead of dropping to 0 a priority change of a waiting thread, of a timed-out thread that has not run yet or from a timer callback takes effect without corrupting the wait a round-robin time slice is armed at dispatch and refilled after a timed wait
			PTHREAD_INHERIT_SCHED inherits the creator’s scheduling policy and own priority pthread_create() and pthread_mutex_init() reject attribute values their setters would not store pthread_attr_setschedparam() and the stack setters reject out-of-range values the initial stack pointer of a new thread is 8-byte aligned a detached thread’s stack is freed after its last context switch, and cleanup handlers run before the stack is freed NULL arguments to pthread_cancel(), pthread_setschedprio(), pthread_setprivilege_np() and four mutex getters return EINVAL, and pthread_getname_np() with a zero length returns ERANGE
			PTHREAD_MUTEX_INITIALIZER compiles with GCC 14 and later pthread_mutex_timedlock() and pthread_mutex_clocklock() return ETIMEDOUT or EINVAL instead of EBUSY relocking a NORMAL mutex from its owner returns EBUSY or times out instead of blocking forever pthread_mutex_setprioceiling() sets the ceiling of an unowned mutex a failed first lock of a statically initialised mutex can be retried
			huge timeouts saturate instead of wrapping and firing at once unsupported clock identifiers are rejected with EINVAL; failing clock calls and timer_create() return -1 instead of 255 the E2BIG error number is corrected timer_settime() rejects a NULL value, disarms with a malformed it_interval and works from the timer’s own callback qrt_systimer_getmonotonic() before the kernel starts returns EINVAL
			sem_init() clears the wait list, and sem_trywait() works from a deferred function mq_open() takes only mq_maxmsg and mq_msgsize from the attributes, which stops a queue still in use being freed on mq_close() mq_getattr() reports O_NONBLOCK, mq_open() rejects sizes that overflow and mq_send() rejects lengths of 16 MiB or more qrt_defer_call() keeps every call from nested interrupts and restores the caller’s interrupt mask
			a wake-up or timeout in the pass that parks a thread returns the correct result, and a retried call keeps the thread’s saved FPU registers intact ARMv8-M MPU: an interrupt arriving during a context switch no longer raises a spurious memory management fault ARMv8-M MPU regions honour the requested shareability, and invalid permissions return EINVAL pthread_cancel() works from a deferred function or timer callback on MPU builds ARMv8-M stack limits are cleared when checking is off, loaded from the right address on Baseline Secure and kept inside the thread’s stack qrt_systimer_configure() writes the timer interrupt’s priority to the right address on ARMv6-M and ARMv8-M Baseline
1.2.0	3	Sep 16, 2026	New: cycle-accurate worst-case execution time (WCET) profiling (QRT_CFG_PERF_ENABLE) and the Profiling chapter the Memory Footprint chapter constant-time O(1) scheduler and kernel services bounded-time kernel heap allocation priority-ordered message queues per-system-call configuration switches boot console and banner showing the version and release date pthread_setfpcontext_np() SEM_VALUE_MAX
			Changed: kernel objects are allocated from the kernel heap, so QRT_CFG_MUTEX_LIST_SIZE, QRT_CFG_MESSAGE_QUEUE_LIMIT, QRT_CFG_MESSAGE_QUEUE_NAME_LIMIT and QRT_CFG_TIMER_LIMIT are removed qrt_fpu_ctxenable() and qrt_fpu_ctxdisable() are replaced by pthread_setfpcontext_np() qrt_systimer_getmonotonic() takes a signed 64-bit count kernel linker sections .text2/.data2/.bss2 are renamed .qrt_text/.qrt_data/.qrt_bss (update custom linker scripts) a system call whose configuration switch is absent from qrt_cfg.h is compiled out and reports ENOSYS, so start from the shipped qrt_cfg.h when upgrading evaluation build limits count live objects
			Fixed: timed pthread waits return ETIMEDOUT instead of -1 nanosleep() intervals no longer truncated to 32 bits scheduling policy from thread attributes honoured at creation opaque POSIX types sized correctly pthread_attr_t sized correctly on MPU-enabled builds MPU region alignment, ARMv7-M memory attribute encoding and thread stack alignment errno access from unprivileged threads monotonic clock reads during a pending timer expiry 8-byte stack alignment in exception handlers demo linker script loads kernel data from flash (warm-reset HardFault)
1.1.1	2	May 9, 2026	Added pthread thread-local storage (pthread_key) and pthread_once()
1.1.0	1	Mar 5, 2026	Added POSIX user-space APIs
1.0.0	0	May 24, 2025	Initial release