t-test-interrupt.c

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

/*
 * 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>

#ifdef RTEMS_SMP
#include <rtems/score/smpimpl.h>
#endif

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;
#ifdef RTEMS_SMP
    Per_CPU_Job job;
    Per_CPU_Job_context job_context;
#endif
    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;
}

#ifdef RTEMS_SMP
static void
T_interrupt_blocked(void *arg)
{
    T_interrupt_context *ctx;

    ctx = arg;
    (*ctx->blocked)(ctx->arg);
}
#endif

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,
#ifdef RTEMS_SMP
    .job = {
        .context = &T_interrupt_instance.job_context
    },
    .job_context = {
        .handler = T_interrupt_blocked,
        .arg = &T_interrupt_instance
    },
#endif
    .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) {
#ifdef RTEMS_SMP
            Per_CPU_Control *cpu_self;

            /*
             * In SMP configurations, the thread switch extension
             * runs in a very restricted environment.  Interrupts
             * are disabled and the caller owns the per-CPU lock.
             * In order to avoid deadlocks at SMP lock level, we
             * have to use an SMP job which runs later in the
             * context of the inter-processor interrupt.
             */
            cpu_self = _Per_CPU_Get();
            _Per_CPU_Add_job(cpu_self, &ctx->job);
            _SMP_Send_message(_Per_CPU_Get_index(cpu_self),
                SMP_MESSAGE_PERFORM_JOBS);
#else
            (*ctx->blocked)(ctx->arg);
#endif
        }
    }
}

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 const 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;
}