job.c

/*
 * Background jobs (long-running operations)
 *
 * Copyright (c) 2011 IBM Corp.
 * Copyright (c) 2012, 2018 Red Hat, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "qemu/osdep.h"
#include "qemu-common.h"
#include "qapi/error.h"
#include "qemu/job.h"
#include "qemu/id.h"
#include "qemu/main-loop.h"
#include "trace-root.h"

static QLIST_HEAD(, Job) jobs = QLIST_HEAD_INITIALIZER(jobs);

/* Job State Transition Table */
bool JobSTT[JOB_STATUS__MAX][JOB_STATUS__MAX] = {
                                    /* U, C, R, P, Y, S, W, D, X, E, N */
    /* U: */ [JOB_STATUS_UNDEFINED] = {0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0},
    /* C: */ [JOB_STATUS_CREATED]   = {0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1},
    /* R: */ [JOB_STATUS_RUNNING]   = {0, 0, 0, 1, 1, 0, 1, 0, 1, 0, 0},
    /* P: */ [JOB_STATUS_PAUSED]    = {0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0},
    /* Y: */ [JOB_STATUS_READY]     = {0, 0, 0, 0, 0, 1, 1, 0, 1, 0, 0},
    /* S: */ [JOB_STATUS_STANDBY]   = {0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0},
    /* W: */ [JOB_STATUS_WAITING]   = {0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0},
    /* D: */ [JOB_STATUS_PENDING]   = {0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0},
    /* X: */ [JOB_STATUS_ABORTING]  = {0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0},
    /* E: */ [JOB_STATUS_CONCLUDED] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
    /* N: */ [JOB_STATUS_NULL]      = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
};

bool JobVerbTable[JOB_VERB__MAX][JOB_STATUS__MAX] = {
                                    /* U, C, R, P, Y, S, W, D, X, E, N */
    [JOB_VERB_CANCEL]               = {0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0},
    [JOB_VERB_PAUSE]                = {0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0},
    [JOB_VERB_RESUME]               = {0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0},
    [JOB_VERB_SET_SPEED]            = {0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0},
    [JOB_VERB_COMPLETE]             = {0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0},
    [JOB_VERB_FINALIZE]             = {0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0},
    [JOB_VERB_DISMISS]              = {0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0},
};

/* Right now, this mutex is only needed to synchronize accesses to job->busy
 * and job->sleep_timer, such as concurrent calls to job_do_yield and
 * job_enter. */
static QemuMutex job_mutex;

static void job_lock(void)
{
    qemu_mutex_lock(&job_mutex);
}

static void job_unlock(void)
{
    qemu_mutex_unlock(&job_mutex);
}

static void __attribute__((__constructor__)) job_init(void)
{
    qemu_mutex_init(&job_mutex);
}

/* TODO Make static once the whole state machine is in job.c */
void job_state_transition(Job *job, JobStatus s1)
{
    JobStatus s0 = job->status;
    assert(s1 >= 0 && s1 <= JOB_STATUS__MAX);
    trace_job_state_transition(job, /* TODO re-enable: job->ret */ 0,
                               JobSTT[s0][s1] ? "allowed" : "disallowed",
                               JobStatus_str(s0), JobStatus_str(s1));
    assert(JobSTT[s0][s1]);
    job->status = s1;
}

int job_apply_verb(Job *job, JobVerb verb, Error **errp)
{
    JobStatus s0 = job->status;
    assert(verb >= 0 && verb <= JOB_VERB__MAX);
    trace_job_apply_verb(job, JobStatus_str(s0), JobVerb_str(verb),
                         JobVerbTable[verb][s0] ? "allowed" : "prohibited");
    if (JobVerbTable[verb][s0]) {
        return 0;
    }
    error_setg(errp, "Job '%s' in state '%s' cannot accept command verb '%s'",
               job->id, JobStatus_str(s0), JobVerb_str(verb));
    return -EPERM;
}

JobType job_type(const Job *job)
{
    return job->driver->job_type;
}

const char *job_type_str(const Job *job)
{
    return JobType_str(job_type(job));
}

bool job_is_cancelled(Job *job)
{
    return job->cancelled;
}

bool job_is_completed(Job *job)
{
    switch (job->status) {
    case JOB_STATUS_UNDEFINED:
    case JOB_STATUS_CREATED:
    case JOB_STATUS_RUNNING:
    case JOB_STATUS_PAUSED:
    case JOB_STATUS_READY:
    case JOB_STATUS_STANDBY:
        return false;
    case JOB_STATUS_WAITING:
    case JOB_STATUS_PENDING:
    case JOB_STATUS_ABORTING:
    case JOB_STATUS_CONCLUDED:
    case JOB_STATUS_NULL:
        return true;
    default:
        g_assert_not_reached();
    }
    return false;
}

bool job_started(Job *job)
{
    return job->co;
}

bool job_should_pause(Job *job)
{
    return job->pause_count > 0;
}

Job *job_next(Job *job)
{
    if (!job) {
        return QLIST_FIRST(&jobs);
    }
    return QLIST_NEXT(job, job_list);
}

Job *job_get(const char *id)
{
    Job *job;

    QLIST_FOREACH(job, &jobs, job_list) {
        if (job->id && !strcmp(id, job->id)) {
            return job;
        }
    }

    return NULL;
}

static void job_sleep_timer_cb(void *opaque)
{
    Job *job = opaque;

    job_enter(job);
}

void *job_create(const char *job_id, const JobDriver *driver, AioContext *ctx,
                 Error **errp)
{
    Job *job;

    if (job_id) {
        if (!id_wellformed(job_id)) {
            error_setg(errp, "Invalid job ID '%s'", job_id);
            return NULL;
        }
        if (job_get(job_id)) {
            error_setg(errp, "Job ID '%s' already in use", job_id);
            return NULL;
        }
    }

    job = g_malloc0(driver->instance_size);
    job->driver        = driver;
    job->id            = g_strdup(job_id);
    job->refcnt        = 1;
    job->aio_context   = ctx;
    job->busy          = false;
    job->paused        = true;
    job->pause_count   = 1;

    job_state_transition(job, JOB_STATUS_CREATED);
    aio_timer_init(qemu_get_aio_context(), &job->sleep_timer,
                   QEMU_CLOCK_REALTIME, SCALE_NS,
                   job_sleep_timer_cb, job);

    QLIST_INSERT_HEAD(&jobs, job, job_list);

    return job;
}

void job_ref(Job *job)
{
    ++job->refcnt;
}

void job_unref(Job *job)
{
    if (--job->refcnt == 0) {
        assert(job->status == JOB_STATUS_NULL);
        assert(!timer_pending(&job->sleep_timer));

        if (job->driver->free) {
            job->driver->free(job);
        }

        QLIST_REMOVE(job, job_list);

        g_free(job->id);
        g_free(job);
    }
}

void job_enter_cond(Job *job, bool(*fn)(Job *job))
{
    if (!job_started(job)) {
        return;
    }
    if (job->deferred_to_main_loop) {
        return;
    }

    job_lock();
    if (job->busy) {
        job_unlock();
        return;
    }

    if (fn && !fn(job)) {
        job_unlock();
        return;
    }

    assert(!job->deferred_to_main_loop);
    timer_del(&job->sleep_timer);
    job->busy = true;
    job_unlock();
    aio_co_wake(job->co);
}

void job_enter(Job *job)
{
    job_enter_cond(job, NULL);
}

/* Yield, and schedule a timer to reenter the coroutine after @ns nanoseconds.
 * Reentering the job coroutine with block_job_enter() before the timer has
 * expired is allowed and cancels the timer.
 *
 * If @ns is (uint64_t) -1, no timer is scheduled and block_job_enter() must be
 * called explicitly. */
void coroutine_fn job_do_yield(Job *job, uint64_t ns)
{
    job_lock();
    if (ns != -1) {
        timer_mod(&job->sleep_timer, ns);
    }
    job->busy = false;
    job_unlock();
    qemu_coroutine_yield();

    /* Set by job_enter_cond() before re-entering the coroutine.  */
    assert(job->busy);
}

void coroutine_fn job_pause_point(Job *job)
{
    assert(job && job_started(job));

    if (!job_should_pause(job)) {
        return;
    }
    if (job_is_cancelled(job)) {
        return;
    }

    if (job->driver->pause) {
        job->driver->pause(job);
    }

    if (job_should_pause(job) && !job_is_cancelled(job)) {
        JobStatus status = job->status;
        job_state_transition(job, status == JOB_STATUS_READY
                                  ? JOB_STATUS_STANDBY
                                  : JOB_STATUS_PAUSED);
        job->paused = true;
        job_do_yield(job, -1);
        job->paused = false;
        job_state_transition(job, status);
    }

    if (job->driver->resume) {
        job->driver->resume(job);
    }
}

void coroutine_fn job_sleep_ns(Job *job, int64_t ns)
{
    assert(job->busy);

    /* Check cancellation *before* setting busy = false, too!  */
    if (job_is_cancelled(job)) {
        return;
    }

    if (!job_should_pause(job)) {
        job_do_yield(job, qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + ns);
    }

    job_pause_point(job);
}

/**
 * All jobs must allow a pause point before entering their job proper. This
 * ensures that jobs can be paused prior to being started, then resumed later.
 */
static void coroutine_fn job_co_entry(void *opaque)
{
    Job *job = opaque;

    assert(job && job->driver && job->driver->start);
    job_pause_point(job);
    job->driver->start(job);
}


void job_start(Job *job)
{
    assert(job && !job_started(job) && job->paused &&
           job->driver && job->driver->start);
    job->co = qemu_coroutine_create(job_co_entry, job);
    job->pause_count--;
    job->busy = true;
    job->paused = false;
    job_state_transition(job, JOB_STATUS_RUNNING);
    aio_co_enter(job->aio_context, job->co);
}

/* Assumes the block_job_mutex is held */
static bool job_timer_not_pending(Job *job)
{
    return !timer_pending(&job->sleep_timer);
}

void job_pause(Job *job)
{
    job->pause_count++;
}

void job_resume(Job *job)
{
    assert(job->pause_count > 0);
    job->pause_count--;
    if (job->pause_count) {
        return;
    }

    /* kick only if no timer is pending */
    job_enter_cond(job, job_timer_not_pending);
}

void job_user_pause(Job *job, Error **errp)
{
    if (job_apply_verb(job, JOB_VERB_PAUSE, errp)) {
        return;
    }
    if (job->user_paused) {
        error_setg(errp, "Job is already paused");
        return;
    }
    job->user_paused = true;
    job_pause(job);
}

bool job_user_paused(Job *job)
{
    return job->user_paused;
}

void job_user_resume(Job *job, Error **errp)
{
    assert(job);
    if (!job->user_paused || job->pause_count <= 0) {
        error_setg(errp, "Can't resume a job that was not paused");
        return;
    }
    if (job_apply_verb(job, JOB_VERB_RESUME, errp)) {
        return;
    }
    if (job->driver->user_resume) {
        job->driver->user_resume(job);
    }
    job->user_paused = false;
    job_resume(job);
}


typedef struct {
    Job *job;
    JobDeferToMainLoopFn *fn;
    void *opaque;
} JobDeferToMainLoopData;

static void job_defer_to_main_loop_bh(void *opaque)
{
    JobDeferToMainLoopData *data = opaque;
    Job *job = data->job;
    AioContext *aio_context = job->aio_context;

    aio_context_acquire(aio_context);
    data->fn(data->job, data->opaque);
    aio_context_release(aio_context);

    g_free(data);
}

void job_defer_to_main_loop(Job *job, JobDeferToMainLoopFn *fn, void *opaque)
{
    JobDeferToMainLoopData *data = g_malloc(sizeof(*data));
    data->job = job;
    data->fn = fn;
    data->opaque = opaque;
    job->deferred_to_main_loop = true;

    aio_bh_schedule_oneshot(qemu_get_aio_context(),
                            job_defer_to_main_loop_bh, data);
}