tx_systick_ready.c File Reference

Storage for the ThreadX-ready latch that gates SysTick -> _tx_timer_interrupt. More...

#include <stdint.h>

Include dependency graph for tx_systick_ready.c:

Go to the source code of this file.

Variables
volatile uint32_t	g_ra8_threadx_systick_ready = 0U
	0 until _tx_initialize_low_level has armed ThreadX's SysTick + timer state; 1 afterwards.

Detailed Description

Storage for the ThreadX-ready latch that gates SysTick -> _tx_timer_interrupt.

The shared SysTick handler in libs/ra8_core/src/ra8_time.c takes a weak external reference to _tx_timer_interrupt (issue #8 port- level fix) so any app that links ThreadX gets a ticking kernel timer for free. That works fine when tx_kernel_enter is called back-to-back with ra8_time_init: the SysTick window between them is short enough that no tick fires.

But apps that do a long synchronous job (PHY MDIO bring-up, NetX Duo IP-thread create, USB enumeration setup) between ra8_time_init and tx_kernel_enter give SysTick plenty of time to fire. If the handler calls _tx_timer_interrupt at that point the kernel timer subsystem is still in TX_INITIALIZE_IN_PROGRESS and _tx_timer_expiration_process dereferences a NULL _tx_timer_current_ptr or returns through a stack frame the ISR prologue did not author – the CPU then exception-returns into a value that fails its EXC_RETURN integrity check and HardFaults with UFSR.INVPC == 1.

Reproduced on bench 2026-05-23 with threadx_netx_tcp_echo (CFSR=0x400, HFSR=0x40000000, stacked PC inside __tx_timer_dont_activate).

The fix: this file owns a single volatile uint32_t that starts at 0 (zero-initialised .bss) and is set to 1 by the project's _tx_initialize_low_level (the .S file in this directory) as the very last instruction before it returns to _tx_initialize_kernel_enter. By that point ThreadX has already armed its own SysTick and the timer subsystem is safe to call into.

The shared SysTick handler in ra8_time.c declares g_ra8_threadx_systick_ready as a WEAK EXTERN and skips _tx_timer_interrupt while the flag reads 0. Non-ThreadX apps never link this TU, so the weak extern resolves to NULL and the corresponding if short-circuits at runtime to false.

Copyright

Copyright (c) 2026 Brighton Sikarskie SPDX-License-Identifier: MIT

Since

0.1.0

Definition in file tx_systick_ready.c.

Variable Documentation

g_ra8_threadx_systick_ready

volatile uint32_t g_ra8_threadx_systick_ready = 0U

0 until _tx_initialize_low_level has armed ThreadX's SysTick + timer state; 1 afterwards.

Set by the kernel once tx_initialize_low_level has run.

Read by the shared SysTick handler in libs/ra8_core/src/ra8_time.c.

Note

Single-writer (assembly, once); multi-reader (every SysTick).

Since

0.1.0

Definition at line 58 of file tx_systick_ready.c.

Referenced by _tx_timer_interrupt(), internal_systick_handler(), ns_systick_handler(), and SysTick_Handler().