source: rtems/cpukit/libtest/t-test-interrupt.c @ cc3fd8fc

/* SPDX-License-Identifier: BSD-2-Clause */

/**
 * @file
 *
 * @ingroup RTEMSTestFrameworkImpl
 *
 * @brief Implementation of T_interrupt_test().
 */

/*
 * Copyright (C) 2020 embedded brains GmbH (http://www.embedded-brains.de)
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <rtems/test.h>

#include <rtems/score/atomic.h>
#include <rtems/score/percpu.h>
#include <rtems/score/thread.h>
#include <rtems/score/timecounter.h>
#include <rtems/score/timestampimpl.h>
#include <rtems/score/userextimpl.h>
#include <rtems/score/watchdogimpl.h>

typedef T_interrupt_test_state (*T_interrupt_test_handler)(void *);

#define T_INTERRUPT_SAMPLE_COUNT 8

typedef struct {
        uint_fast32_t one_tick_busy;
        int64_t t0;
        Thread_Control *self;
        Atomic_Uint state;
        void (*prepare)(void *);
        void (*action)(void *);
        T_interrupt_test_state (*interrupt)(void *);
        void (*blocked)(void *);
        void *arg;
        Watchdog_Control wdg;
        User_extensions_Control ext;
        T_fixture_node node;
} T_interrupt_context;

typedef struct {
        int64_t t;
        int64_t d;
} T_interrupt_clock_time;

static void
T_interrupt_sort(T_interrupt_clock_time *ct, size_t n)
{
        size_t i;

        /* Bubble sort */
        for (i = 1; i < n ; ++i) {
                size_t j;

                for (j = 0; j < n - i; ++j) {
                         if (ct[j].d > ct[j + 1].d) {
                                T_interrupt_clock_time tmp;

                                tmp = ct[j];
                                ct[j] = ct[j + 1];
                                ct[j + 1] = tmp;
                         }
                }
        }
}

static int64_t
T_interrupt_time_close_to_tick(void)
{
        Watchdog_Interval c0;
        Watchdog_Interval c1;
        T_interrupt_clock_time ct[12];
        Timestamp_Control t;
        int32_t ns_per_tick;
        size_t i;
        size_t n;

        ns_per_tick = (int32_t)_Watchdog_Nanoseconds_per_tick;
        n = RTEMS_ARRAY_SIZE(ct);
        c0 = _Watchdog_Ticks_since_boot;

        for (i = 0; i < n; ++i) {
                do {
                        c1 = _Watchdog_Ticks_since_boot;
                        t = _Timecounter_Sbinuptime();
                } while (c0 == c1);

                c0 = c1;
                ct[i].t = sbttons(t);
        }

        for (i = 1; i < n; ++i) {
                int64_t d;

                d = (ct[i].t - ct[1].t) % ns_per_tick;

                if (d > ns_per_tick / 2) {
                        d -= ns_per_tick;
                }

                ct[i].d = d;
        }

        /*
         * Use the median and not the arithmetic mean since on simulator
         * platforms there may be outliers.
         */
        T_interrupt_sort(&ct[1], n - 1);
        return ct[1 + (n - 1) / 2].t;
}

static void
T_interrupt_watchdog(Watchdog_Control *wdg)
{
        T_interrupt_context *ctx;
        ISR_Level level;
        T_interrupt_test_state state;
        unsigned int expected;

        ctx = RTEMS_CONTAINER_OF(wdg, T_interrupt_context, wdg);

        _ISR_Local_disable(level);
        _Watchdog_Per_CPU_insert_ticks(&ctx->wdg,
            _Watchdog_Get_CPU(&ctx->wdg), 1);
        _ISR_Local_enable(level);

        state = (*ctx->interrupt)(ctx->arg);

        expected = T_INTERRUPT_TEST_ACTION;
        _Atomic_Compare_exchange_uint(&ctx->state, &expected,
            state, ATOMIC_ORDER_RELAXED, ATOMIC_ORDER_RELAXED);
}

static void
T_interrupt_watchdog_insert(T_interrupt_context *ctx)
{
        ISR_Level level;

        _ISR_Local_disable(level);
        _Watchdog_Per_CPU_insert_ticks(&ctx->wdg, _Per_CPU_Get(), 1);
        _ISR_Local_enable(level);
}

static void
T_interrupt_watchdog_remove(T_interrupt_context *ctx)
{
        ISR_Level level;

        _ISR_Local_disable(level);
        _Watchdog_Per_CPU_remove_ticks(&ctx->wdg);
        _ISR_Local_enable(level);
}

static void
T_interrupt_init_once(T_interrupt_context *ctx)
{
        ctx->t0 = T_interrupt_time_close_to_tick();
        ctx->one_tick_busy = T_get_one_clock_tick_busy();
}

static T_interrupt_test_state
T_interrupt_continue(void *arg)
{
        (void)arg;
        return T_INTERRUPT_TEST_CONTINUE;
}

static void
T_interrupt_do_nothing(void *arg)
{
        (void)arg;
}

static void T_interrupt_thread_switch(Thread_Control *, Thread_Control *);

static T_interrupt_context T_interrupt_instance = {
        .interrupt = T_interrupt_continue,
        .blocked = T_interrupt_do_nothing,
        .wdg = WATCHDOG_INITIALIZER(T_interrupt_watchdog),
        .ext = {
                .Callouts = {
                        .thread_switch = T_interrupt_thread_switch
                }
        }
};

T_interrupt_test_state
T_interrupt_test_change_state(T_interrupt_test_state expected_state,
    T_interrupt_test_state desired_state)
{
        T_interrupt_context *ctx;
        unsigned int expected;

        ctx = &T_interrupt_instance;
        expected = expected_state;
        _Atomic_Compare_exchange_uint(&ctx->state, &expected,
            desired_state, ATOMIC_ORDER_RELAXED, ATOMIC_ORDER_RELAXED);

        return expected;
}

T_interrupt_test_state
T_interrupt_test_get_state(void)
{
        T_interrupt_context *ctx;

        ctx = &T_interrupt_instance;
        return _Atomic_Load_uint(&ctx->state, ATOMIC_ORDER_RELAXED);
}

void
T_interrupt_test_busy_wait_for_interrupt(void)
{
        T_interrupt_context *ctx;
        unsigned int state;

        ctx = &T_interrupt_instance;

        do {
                state = _Atomic_Load_uint(&ctx->state, ATOMIC_ORDER_RELAXED);
        } while (state == T_INTERRUPT_TEST_ACTION);
}

static void
T_interrupt_thread_switch(Thread_Control *executing, Thread_Control *heir)
{
        T_interrupt_context *ctx;

        (void)heir;
        ctx = &T_interrupt_instance;

        if (ctx->self == executing) {
                T_interrupt_test_state state;

                state = _Atomic_Load_uint(&ctx->state, ATOMIC_ORDER_RELAXED);

                if (state != T_INTERRUPT_TEST_INITIAL) {
                        (*ctx->blocked)(ctx->arg);
                }
        }
}

static T_interrupt_context *
T_interrupt_setup(const T_interrupt_test_config *config, void *arg)
{
        T_interrupt_context *ctx;

        T_quiet_assert_not_null(config->action);
        T_quiet_assert_not_null(config->interrupt);
        ctx = &T_interrupt_instance;
        ctx->self = _Thread_Get_executing();
        ctx->arg = arg;
        ctx->interrupt = config->interrupt;

        if (config->blocked != NULL) {
                ctx->blocked = config->blocked;
        }

        if (ctx->t0 == 0) {
                T_interrupt_init_once(ctx);
        }

        _User_extensions_Add_set(&ctx->ext);
        T_interrupt_watchdog_insert(ctx);
        return ctx;
}

static void
T_interrupt_teardown(void *arg)
{
        T_interrupt_context *ctx;

        ctx = arg;
        ctx->interrupt = T_interrupt_continue;
        ctx->blocked = T_interrupt_do_nothing;
        T_interrupt_watchdog_remove(ctx);
        _User_extensions_Remove_set(&ctx->ext);
        ctx->self = NULL;
        ctx->arg = NULL;
}

static T_fixture T_interrupt_fixture = {
        .teardown = T_interrupt_teardown,
        .initial_context = &T_interrupt_instance
};

T_interrupt_test_state
T_interrupt_test(const T_interrupt_test_config *config, void *arg)
{
        T_interrupt_context *ctx;
        uint_fast32_t lower_bound[T_INTERRUPT_SAMPLE_COUNT];
        uint_fast32_t upper_bound[T_INTERRUPT_SAMPLE_COUNT];
        uint_fast32_t lower_sum;
        uint_fast32_t upper_sum;
        int32_t ns_per_tick;
        size_t sample;
        uint32_t iter;

        ctx = T_interrupt_setup(config, arg);
        T_push_fixture(&ctx->node, &T_interrupt_fixture);
        ns_per_tick = (int32_t)_Watchdog_Nanoseconds_per_tick;
        lower_sum = 0;
        upper_sum = T_INTERRUPT_SAMPLE_COUNT * ctx->one_tick_busy;

        for (sample = 0; sample < T_INTERRUPT_SAMPLE_COUNT; ++sample) {
                lower_bound[sample] = 0;
                upper_bound[sample] = ctx->one_tick_busy;
        }

        sample = 0;

        for (iter = 0; iter < config->max_iteration_count; ++iter) {
                T_interrupt_test_state state;
                int64_t t;
                int64_t d;
                Timestamp_Control s1;
                Timestamp_Control s0;
                uint_fast32_t busy;
                uint_fast32_t delta;

                if (config->prepare != NULL) {
                        (*config->prepare)(arg);
                }

                /*
                 * We use some sort of a damped bisection to find the right
                 * interrupt time point.
                 */
                busy = (lower_sum + upper_sum) /
                    (2 * T_INTERRUPT_SAMPLE_COUNT);

                t = sbttons(_Timecounter_Sbinuptime());
                d = (t - ctx->t0) % ns_per_tick;
                t += ns_per_tick / 4 - d;

                if (d > ns_per_tick / 8) {
                        t += ns_per_tick;
                }

                /*
                 * The s1 value is a future time point close to 25% of a clock
                 * tick interval.
                 */
                s1 = nstosbt(t);

                /*
                 * The path from here to the action call must avoid anything
                 * which can cause jitters.  We wait until 25% of the clock
                 * tick interval are elapsed using the timecounter.  Then we do
                 * a busy wait and call the action.  The interrupt time point
                 * is controlled by the busy count.
                 */

                do {
                        s0 = _Timecounter_Sbinuptime();
                } while (s0 < s1);

                _Atomic_Store_uint(&ctx->state, T_INTERRUPT_TEST_ACTION,
                    ATOMIC_ORDER_RELAXED);
                T_busy(busy);
                (*config->action)(arg);

                state = _Atomic_Exchange_uint(&ctx->state,
                    T_INTERRUPT_TEST_INITIAL, ATOMIC_ORDER_RELAXED);

                if (state == T_INTERRUPT_TEST_DONE) {
                        break;
                }

                /* Adjust the lower/upper bound of the bisection interval */
                if (state == T_INTERRUPT_TEST_EARLY) {
                        uint_fast32_t lower;

                        upper_sum -= upper_bound[sample];
                        upper_sum += busy;
                        upper_bound[sample] = busy;

                        /* Round down to make sure no underflow happens */
                        lower = lower_bound[sample];
                        delta = lower / 32;
                        lower_sum -= delta;
                        lower_bound[sample] = lower - delta;

                        sample = (sample + 1) % T_INTERRUPT_SAMPLE_COUNT;
                } else if (state == T_INTERRUPT_TEST_LATE) {
                        uint_fast32_t upper;

                        lower_sum -= lower_bound[sample];
                        lower_sum += busy;
                        lower_bound[sample] = busy;

                        /*
                         * The one tick busy count value is not really
                         * trustable on some platforms.  Allow the upper bound
                         * to grow over this value in time.
                         */
                        upper = upper_bound[sample];
                        delta = (upper + 31) / 32;
                        upper_sum += delta;
                        upper_bound[sample] = upper + delta;

                        sample = (sample + 1) % T_INTERRUPT_SAMPLE_COUNT;
                }
        }

        T_pop_fixture();

        if (iter == config->max_iteration_count) {
                return T_INTERRUPT_TEST_TIMEOUT;
        }

        return T_INTERRUPT_TEST_DONE;
}