modules: release kernel stack when deleting module threads

[prashit-vora]

Fixes #400.

User-mode module threads allocate a separate kernel stack from the module object pool. The thread-delete dispatcher freed the TX_THREAD object but left that kernel stack allocated.

This change releases the kernel stack after _txe_thread_delete() succeeds and before releasing the thread object.

Testing:

• Built the Cortex-M3 GNU module and module-manager images.
• Ran the reproduction in QEMU using mps2-an385.
• Without the fix, tx_thread_create() returned TX_NO_MEMORY after 18 create/delete cycles.
• With the fix, all 64 cycles completed.

Temporary QEMU reproduction

#define TXM_MODULE

#include "txm_module.h"

#define LEAK_TEST_ITERATION_COUNT  64
#define LEAK_TEST_STACK_SIZE       512

#define LEAK_TEST_PASS             0x600D600DUL
#define LEAK_TEST_ALLOCATE_FAILED  0xA1000000UL
#define LEAK_TEST_CREATE_FAILED    0xA2000000UL
#define LEAK_TEST_TERMINATE_FAILED 0xA3000000UL
#define LEAK_TEST_DELETE_FAILED    0xA4000000UL

TX_THREAD     *leak_test_thread_ptr;
ULONG          leak_test_stack[LEAK_TEST_STACK_SIZE / sizeof(ULONG)];
volatile ULONG leak_test_iterations;
volatile ULONG leak_test_result;

static void leak_test_thread_entry(ULONG input)
{
    (void) input;
}

void demo_module_start(ULONG id)
{
UINT iteration;
UINT status;

    (void) id;
    leak_test_iterations = 0;
    leak_test_result = 0;

    for (iteration = 0; iteration < LEAK_TEST_ITERATION_COUNT; iteration++)
    {
        status = txm_module_object_allocate((VOID **) &leak_test_thread_ptr,
                                            sizeof(TX_THREAD));
        if (status != TX_SUCCESS)
        {
            leak_test_result = LEAK_TEST_ALLOCATE_FAILED | status;
            break;
        }

        status = tx_thread_create(leak_test_thread_ptr, "leak test thread",
                                  leak_test_thread_entry, 0,
                                  leak_test_stack, sizeof(leak_test_stack),
                                  16, 16, TX_NO_TIME_SLICE, TX_DONT_START);
        if (status != TX_SUCCESS)
        {
            leak_test_result = LEAK_TEST_CREATE_FAILED | status;
            break;
        }

        status = tx_thread_terminate(leak_test_thread_ptr);
        if (status != TX_SUCCESS)
        {
            leak_test_result = LEAK_TEST_TERMINATE_FAILED | status;
            break;
        }

        status = tx_thread_delete(leak_test_thread_ptr);
        if (status != TX_SUCCESS)
        {
            leak_test_result = LEAK_TEST_DELETE_FAILED | status;
            break;
        }

        leak_test_iterations = iteration + 1;
    }

    if (leak_test_iterations == LEAK_TEST_ITERATION_COUNT)
    {
        leak_test_result = LEAK_TEST_PASS;
    }

}

QEMU results

Parent revision without the fix:
leak_test_iterations = 18
leak_test_result = 0xA2000010
                       ^ create failed with TX_NO_MEMORY

Revision with the fix:
leak_test_iterations = 64
leak_test_result = 0x600D600D
                       ^ pass

NOTE: This was not tested on physical hardware.

[prashit-vora]

Hi @fdesbiens, Could you approve the workflow runs for this PR?

[prashit-vora]

@fdesbiens could you review it ? i think its ready to merge.