rust/src/rt/rust_task_thread.cpp

#include <stdarg.h>
#include <cassert>
#include <pthread.h>
#include "rust_internal.h"
#include "rust_util.h"
#include "globals.h"
#include "rust_scheduler.h"

#ifndef _WIN32
pthread_key_t rust_task_thread::task_key;
#else
DWORD rust_task_thread::task_key;
#endif

bool rust_task_thread::tls_initialized = false;

rust_task_thread::rust_task_thread(rust_scheduler *sched,
                                   rust_srv *srv,
                                   int id) :
    ref_count(1),
    _log(srv, this),
    log_lvl(log_debug),
    srv(srv),
    // TODO: calculate a per scheduler name.
    name("main"),
    newborn_tasks(this, "newborn"),
    running_tasks(this, "running"),
    blocked_tasks(this, "blocked"),
    dead_tasks(this, "dead"),
    cache(this),
    kernel(sched->kernel),
    sched(sched),
    id(id),
    min_stack_size(kernel->env->min_stack_size),
    env(kernel->env),
    should_exit(false)
{
    LOGPTR(this, "new dom", (uintptr_t)this);
    isaac_init(kernel, &rctx);
#ifndef __WIN32__
    pthread_attr_init(&attr);
    pthread_attr_setstacksize(&attr, 1024 * 1024);
    pthread_attr_setdetachstate(&attr, true);
#endif

    if (!tls_initialized)
        init_tls();
}

rust_task_thread::~rust_task_thread() {
    DLOG(this, dom, "~rust_task_thread %s @0x%" PRIxPTR, name, (uintptr_t)this);

    newborn_tasks.delete_all();
    running_tasks.delete_all();
    blocked_tasks.delete_all();
    dead_tasks.delete_all();
#ifndef __WIN32__
    pthread_attr_destroy(&attr);
#endif
}

void
rust_task_thread::activate(rust_task *task) {
    task->ctx.next = &c_context;
    DLOG(this, task, "descheduling...");
    lock.unlock();
    task->ctx.swap(c_context);
    lock.lock();
    DLOG(this, task, "task has returned");
}

void
rust_task_thread::log(rust_task* task, uint32_t level, char const *fmt, ...) {
    char buf[BUF_BYTES];
    va_list args;
    va_start(args, fmt);
    vsnprintf(buf, sizeof(buf), fmt, args);
    _log.trace_ln(task, level, buf);
    va_end(args);
}

void
rust_task_thread::fail() {
    log(NULL, log_err, "domain %s @0x%" PRIxPTR " root task failed",
        name, this);
    kernel->fail();
}

void
rust_task_thread::kill_all_tasks() {
    I(this, !lock.lock_held_by_current_thread());
    scoped_lock with(lock);

    for (size_t i = 0; i < running_tasks.length(); i++) {
        // We don't want the failure of these tasks to propagate back
        // to the kernel again since we're already failing everything
        running_tasks[i]->unsupervise();
        running_tasks[i]->kill();
    }

    for (size_t i = 0; i < blocked_tasks.length(); i++) {
        blocked_tasks[i]->unsupervise();
        blocked_tasks[i]->kill();
    }
}

size_t
rust_task_thread::number_of_live_tasks() {
    return running_tasks.length() + blocked_tasks.length();
}

/**
 * Delete any dead tasks.
 */
void
rust_task_thread::reap_dead_tasks() {
    I(this, lock.lock_held_by_current_thread());
    if (dead_tasks.length() == 0) {
        return;
    }

    // First make a copy of the dead_task list with the lock held
    size_t dead_tasks_len = dead_tasks.length();
    rust_task **dead_tasks_copy = (rust_task**)
        srv->malloc(sizeof(rust_task*) * dead_tasks_len);
    for (size_t i = 0; i < dead_tasks_len; ++i) {
        dead_tasks_copy[i] = dead_tasks.pop_value();
    }

    // Now unlock again because we have to actually free the dead tasks,
    // and that may end up wanting to lock the kernel lock. We have
    // a kernel lock -> scheduler lock locking order that we need
    // to maintain.
    lock.unlock();

    for (size_t i = 0; i < dead_tasks_len; ++i) {
        rust_task *task = dead_tasks_copy[i];
        if (task) {
            kernel->release_task_id(task->user.id);
            task->deref();
        }
    }
    srv->free(dead_tasks_copy);

    lock.lock();
}

/**
 * Schedules a running task for execution. Only running tasks can be
 * activated.  Blocked tasks have to be unblocked before they can be
 * activated.
 *
 * Returns NULL if no tasks can be scheduled.
 */
rust_task *
rust_task_thread::schedule_task() {
    I(this, this);
    // FIXME: in the face of failing tasks, this is not always right.
    // I(this, n_live_tasks() > 0);
    if (running_tasks.length() > 0) {
        size_t k = isaac_rand(&rctx);
        // Look around for a runnable task, starting at k.
        for(size_t j = 0; j < running_tasks.length(); ++j) {
            size_t  i = (j + k) % running_tasks.length();
            return (rust_task *)running_tasks[i];
        }
    }
    return NULL;
}

void
rust_task_thread::log_state() {
    if (log_rt_task < log_debug) return;

    if (!running_tasks.is_empty()) {
        log(NULL, log_debug, "running tasks:");
        for (size_t i = 0; i < running_tasks.length(); i++) {
            log(NULL, log_debug, "\t task: %s @0x%" PRIxPTR,
                running_tasks[i]->name,
                running_tasks[i]);
        }
    }

    if (!blocked_tasks.is_empty()) {
        log(NULL, log_debug, "blocked tasks:");
        for (size_t i = 0; i < blocked_tasks.length(); i++) {
            log(NULL, log_debug, "\t task: %s @0x%" PRIxPTR ", blocked on: 0x%"
                PRIxPTR " '%s'",
                blocked_tasks[i]->name, blocked_tasks[i],
                blocked_tasks[i]->cond, blocked_tasks[i]->cond_name);
        }
    }

    if (!dead_tasks.is_empty()) {
        log(NULL, log_debug, "dead tasks:");
        for (size_t i = 0; i < dead_tasks.length(); i++) {
            log(NULL, log_debug, "\t task: %s 0x%" PRIxPTR,
                dead_tasks[i]->name, dead_tasks[i]);
        }
    }
}
/**
 * Starts the main scheduler loop which performs task scheduling for this
 * domain.
 *
 * Returns once no more tasks can be scheduled and all task ref_counts
 * drop to zero.
 */
void
rust_task_thread::start_main_loop() {
    lock.lock();

    DLOG(this, dom, "started domain loop %d", id);

    while (!should_exit) {
        DLOG(this, dom, "worker %d, number_of_live_tasks = %d",
             id, number_of_live_tasks());

        rust_task *scheduled_task = schedule_task();

        if (scheduled_task == NULL) {
            log_state();
            DLOG(this, task,
                 "all tasks are blocked, scheduler id %d yielding ...",
                 id);
            lock.wait();
            reap_dead_tasks();
            DLOG(this, task,
                 "scheduler %d resuming ...", id);
            continue;
        }

        I(this, scheduled_task->running());

        DLOG(this, task,
             "activating task %s 0x%" PRIxPTR
             ", sp=0x%" PRIxPTR
             ", state: %s",
             scheduled_task->name,
             (uintptr_t)scheduled_task,
             scheduled_task->user.rust_sp,
             scheduled_task->state->name);

        place_task_in_tls(scheduled_task);

        DLOG(this, task,
             "Running task %p on worker %d",
             scheduled_task, id);
        activate(scheduled_task);

        DLOG(this, task,
             "returned from task %s @0x%" PRIxPTR
             " in state '%s', sp=0x%x, worker id=%d" PRIxPTR,
             scheduled_task->name,
             (uintptr_t)scheduled_task,
             scheduled_task->state->name,
             scheduled_task->user.rust_sp,
             id);

        reap_dead_tasks();
    }

    A(this, newborn_tasks.is_empty(), "Should have no newborn tasks");
    A(this, running_tasks.is_empty(), "Should have no running tasks");
    A(this, blocked_tasks.is_empty(), "Should have no blocked tasks");
    A(this, dead_tasks.is_empty(), "Should have no dead tasks");

    DLOG(this, dom, "finished main-loop %d", id);

    lock.unlock();
}

rust_crate_cache *
rust_task_thread::get_cache() {
    return &cache;
}

rust_task_id
rust_task_thread::create_task(rust_task *spawner, const char *name,
                            size_t init_stack_sz) {
    rust_task *task =
        new (this->kernel, "rust_task")
        rust_task (this, &newborn_tasks, spawner, name, init_stack_sz);
    DLOG(this, task, "created task: " PTR ", spawner: %s, name: %s",
                        task, spawner ? spawner->name : "null", name);

    {
        scoped_lock with(lock);
        newborn_tasks.append(task);
    }

    kernel->register_task(task);
    return task->user.id;
}

void rust_task_thread::run() {
    this->start_main_loop();
    sched->release_task_thread();
}

#ifndef _WIN32
void
rust_task_thread::init_tls() {
    int result = pthread_key_create(&task_key, NULL);
    assert(!result && "Couldn't create the TLS key!");
    tls_initialized = true;
}

void
rust_task_thread::place_task_in_tls(rust_task *task) {
    int result = pthread_setspecific(task_key, task);
    assert(!result && "Couldn't place the task in TLS!");
    task->record_stack_limit();
}

rust_task *
rust_task_thread::get_task() {
    if (!tls_initialized)
        return NULL;
    rust_task *task = reinterpret_cast<rust_task *>
        (pthread_getspecific(task_key));
    assert(task && "Couldn't get the task from TLS!");
    return task;
}
#else
void
rust_task_thread::init_tls() {
    task_key = TlsAlloc();
    assert(task_key != TLS_OUT_OF_INDEXES && "Couldn't create the TLS key!");
    tls_initialized = true;
}

void
rust_task_thread::place_task_in_tls(rust_task *task) {
    BOOL result = TlsSetValue(task_key, task);
    assert(result && "Couldn't place the task in TLS!");
    task->record_stack_limit();
}

rust_task *
rust_task_thread::get_task() {
    if (!tls_initialized)
        return NULL;
    rust_task *task = reinterpret_cast<rust_task *>(TlsGetValue(task_key));
    assert(task && "Couldn't get the task from TLS!");
    return task;
}
#endif

void
rust_task_thread::exit() {
    A(this, !lock.lock_held_by_current_thread(), "Shouldn't have lock");
    scoped_lock with(lock);
    should_exit = true;
    lock.signal();
}

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