/*

 * Copyright © 2018, VideoLAN and dav1d authors

 * Copyright © 2018, Two Orioles, LLC

 * All rights reserved.

 *

 * 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.

 */

#include "config.h"

#include "common/frame.h"

#include "src/thread_task.h"

#include "src/fg_apply.h"

// This function resets the cur pointer to the first frame theoretically

// executable after a task completed (ie. each time we update some progress or

// insert some tasks in the queue).

// When frame_idx is set, it can be either from a completed task, or from tasks

// inserted in the queue, in which case we have to make sure the cur pointer

// isn't past this insert.

// The special case where frame_idx is UINT_MAX is to handle the reset after

// completing a task and locklessly signaling progress. In this case we don't

// enter a critical section, which is needed for this function, so we set an

// atomic for a delayed handling, happening here. Meaning we can call this

// function without any actual update other than what's in the atomic, hence

// this special case.

static inline int reset_task_cur(const Dav1dContext *const c,

                                 struct TaskThreadData *const ttd,

                                 unsigned frame_idx)

{

    const unsigned first = atomic_load(&ttd->first);

    unsigned reset_frame_idx = atomic_exchange(&ttd->reset_task_cur, UINT_MAX);

    if (reset_frame_idx < first) {

        if (frame_idx == UINT_MAX) return 0;

        reset_frame_idx = UINT_MAX;

    }

    if (!ttd->cur && c->fc[first].task_thread.task_cur_prev == NULL)

        return 0;

    if (reset_frame_idx != UINT_MAX) {

        if (frame_idx == UINT_MAX) {

            if (reset_frame_idx > first + ttd->cur)

                return 0;

            ttd->cur = reset_frame_idx - first;

            goto cur_found;

        }

    } else if (frame_idx == UINT_MAX)

        return 0;

    if (frame_idx < first) frame_idx += c->n_fc;

    const unsigned min_frame_idx = umin(reset_frame_idx, frame_idx);

    const unsigned cur_frame_idx = first + ttd->cur;

    if (ttd->cur < c->n_fc && cur_frame_idx < min_frame_idx)

        return 0;

    for (ttd->cur = min_frame_idx - first; ttd->cur < c->n_fc; ttd->cur++)

        if (c->fc[(first + ttd->cur) % c->n_fc].task_thread.task_head)

            break;

cur_found:

    for (unsigned i = ttd->cur; i < c->n_fc; i++)

        c->fc[(first + i) % c->n_fc].task_thread.task_cur_prev = NULL;

    return 1;

}

static inline void reset_task_cur_async(struct TaskThreadData *const ttd,

                                        unsigned frame_idx, unsigned n_frames)

{

    const unsigned first = atomic_load(&ttd->first);

    if (frame_idx < first) frame_idx += n_frames;

    unsigned last_idx = frame_idx;

    do {

        frame_idx = last_idx;

        last_idx = atomic_exchange(&ttd->reset_task_cur, frame_idx);

    } while (last_idx < frame_idx);

    if (frame_idx == first && atomic_load(&ttd->first) != first) {

        unsigned expected = frame_idx;

        atomic_compare_exchange_strong(&ttd->reset_task_cur, &expected, UINT_MAX);

    }

}

static void insert_tasks_between(Dav1dFrameContext *const f,

                                 Dav1dTask *const first, Dav1dTask *const last,

                                 Dav1dTask *const a, Dav1dTask *const b,

                                 const int cond_signal)

{

    struct TaskThreadData *const ttd = f->task_thread.ttd;

    if (atomic_load(f->c->flush)) return;

    assert(!a || a->next == b);

    if (!a) f->task_thread.task_head = first;

    else a->next = first;

    if (!b) f->task_thread.task_tail = last;

    last->next = b;

    reset_task_cur(f->c, ttd, first->frame_idx);

    if (cond_signal && !atomic_fetch_or(&ttd->cond_signaled, 1))

        pthread_cond_signal(&ttd->cond);

}

static void insert_tasks(Dav1dFrameContext *const f,

                         Dav1dTask *const first, Dav1dTask *const last,

                         const int cond_signal)

{

    // insert task back into task queue

    Dav1dTask *t_ptr, *prev_t = NULL;

    for (t_ptr = f->task_thread.task_head;

         t_ptr; prev_t = t_ptr, t_ptr = t_ptr->next)

    {

        // entropy coding precedes other steps

        if (t_ptr->type == DAV1D_TASK_TYPE_TILE_ENTROPY) {

            if (first->type > DAV1D_TASK_TYPE_TILE_ENTROPY) continue;

            // both are entropy

            if (first->sby > t_ptr->sby) continue;

            if (first->sby < t_ptr->sby) {

                insert_tasks_between(f, first, last, prev_t, t_ptr, cond_signal);

                return;

            }

            // same sby

        } else {

            if (first->type == DAV1D_TASK_TYPE_TILE_ENTROPY) {

                insert_tasks_between(f, first, last, prev_t, t_ptr, cond_signal);

                return;

            }

            if (first->sby > t_ptr->sby) continue;

            if (first->sby < t_ptr->sby) {

                insert_tasks_between(f, first, last, prev_t, t_ptr, cond_signal);

                return;

            }

            // same sby

            if (first->type > t_ptr->type) continue;

            if (first->type < t_ptr->type) {

                insert_tasks_between(f, first, last, prev_t, t_ptr, cond_signal);

                return;

            }

            // same task type

        }

        // sort by tile-id

        assert(first->type == DAV1D_TASK_TYPE_TILE_RECONSTRUCTION ||

               first->type == DAV1D_TASK_TYPE_TILE_ENTROPY);

        assert(first->type == t_ptr->type);

        assert(t_ptr->sby == first->sby);

        const int p = first->type == DAV1D_TASK_TYPE_TILE_ENTROPY;

        const int t_tile_idx = (int) (first - f->task_thread.tile_tasks[p]);

        const int p_tile_idx = (int) (t_ptr - f->task_thread.tile_tasks[p]);

        assert(t_tile_idx != p_tile_idx);

        if (t_tile_idx > p_tile_idx) continue;

        insert_tasks_between(f, first, last, prev_t, t_ptr, cond_signal);

        return;

    }

    // append at the end

    insert_tasks_between(f, first, last, prev_t, NULL, cond_signal);

}

static inline void insert_task(Dav1dFrameContext *const f,

                               Dav1dTask *const t, const int cond_signal)

{

    insert_tasks(f, t, t, cond_signal);

}

static inline void add_pending(Dav1dFrameContext *const f, Dav1dTask *const t) {

    pthread_mutex_lock(&f->task_thread.pending_tasks.lock);

    t->next = NULL;

    if (!f->task_thread.pending_tasks.head)

        f->task_thread.pending_tasks.head = t;

    else

        f->task_thread.pending_tasks.tail->next = t;

    f->task_thread.pending_tasks.tail = t;

    atomic_store(&f->task_thread.pending_tasks.merge, 1);

    pthread_mutex_unlock(&f->task_thread.pending_tasks.lock);

}

static inline int merge_pending_frame(Dav1dFrameContext *const f) {

    int const merge = atomic_load(&f->task_thread.pending_tasks.merge);

    if (merge) {

        pthread_mutex_lock(&f->task_thread.pending_tasks.lock);

        Dav1dTask *t = f->task_thread.pending_tasks.head;

        f->task_thread.pending_tasks.head = NULL;

        f->task_thread.pending_tasks.tail = NULL;

        atomic_store(&f->task_thread.pending_tasks.merge, 0);

        pthread_mutex_unlock(&f->task_thread.pending_tasks.lock);

        while (t) {

            Dav1dTask *const tmp = t->next;

            insert_task(f, t, 0);

            t = tmp;

        }

    }

    return merge;

}

static inline int merge_pending(const Dav1dContext *const c) {

    int res = 0;

    for (unsigned i = 0; i < c->n_fc; i++)

        res |= merge_pending_frame(&c->fc[i]);

    return res;

}

static int create_filter_sbrow(Dav1dFrameContext *const f,

                               const int pass, Dav1dTask **res_t)

{

    const int has_deblock = f->frame_hdr->loopfilter.level_y[0] ||

                            f->frame_hdr->loopfilter.level_y[1];

    const int has_cdef = f->seq_hdr->cdef;

    const int has_resize = f->frame_hdr->width[0] != f->frame_hdr->width[1];

    const int has_lr = f->lf.restore_planes;

    Dav1dTask *tasks = f->task_thread.tasks;

    const int uses_2pass = f->c->n_fc > 1;

    int num_tasks = f->sbh * (1 + uses_2pass);

    if (num_tasks > f->task_thread.num_tasks) {

        const size_t size = sizeof(Dav1dTask) * num_tasks;

        tasks = dav1d_realloc(ALLOC_COMMON_CTX, f->task_thread.tasks, size);

        if (!tasks) return -1;

        memset(tasks, 0, size);

        f->task_thread.tasks = tasks;

        f->task_thread.num_tasks = num_tasks;

    }

    tasks += f->sbh * (pass & 1);

    if (pass & 1) {

        f->frame_thread.entropy_progress = 0;

    } else {

        const int prog_sz = ((f->sbh + 31) & ~31) >> 5;

        if (prog_sz > f->frame_thread.prog_sz) {

            atomic_uint *const prog = dav1d_realloc(ALLOC_COMMON_CTX, f->frame_thread.frame_progress,

                                                    2 * prog_sz * sizeof(*prog));

            if (!prog) return -1;

            f->frame_thread.frame_progress = prog;

            f->frame_thread.copy_lpf_progress = prog + prog_sz;

        }

        f->frame_thread.prog_sz = prog_sz;

        memset(f->frame_thread.frame_progress, 0, prog_sz * sizeof(atomic_uint));

        memset(f->frame_thread.copy_lpf_progress, 0, prog_sz * sizeof(atomic_uint));

        atomic_store(&f->frame_thread.deblock_progress, 0);

    }

    f->frame_thread.next_tile_row[pass & 1] = 0;

    Dav1dTask *t = &tasks[0];

    t->sby = 0;

    t->recon_progress = 1;

    t->deblock_progress = 0;

    t->type = pass == 1 ? DAV1D_TASK_TYPE_ENTROPY_PROGRESS :

              has_deblock ? DAV1D_TASK_TYPE_DEBLOCK_COLS :

              has_cdef || has_lr /* i.e. LR backup */ ? DAV1D_TASK_TYPE_DEBLOCK_ROWS :

              has_resize ? DAV1D_TASK_TYPE_SUPER_RESOLUTION :

              DAV1D_TASK_TYPE_RECONSTRUCTION_PROGRESS;

    t->frame_idx = (int)(f - f->c->fc);

    *res_t = t;

    return 0;

}

int dav1d_task_create_tile_sbrow(Dav1dFrameContext *const f, const int pass,

                                 const int cond_signal)

{

    Dav1dTask *tasks = f->task_thread.tile_tasks[0];

    const int uses_2pass = f->c->n_fc > 1;

    const int n_tasks_per_pass = f->frame_hdr->tiling.cols * f->frame_hdr->tiling.rows;

    const int n_tasks = n_tasks_per_pass * (1 + uses_2pass);

    if (pass < 2) {

        if (n_tasks > f->task_thread.num_tile_tasks) {

            const size_t size = sizeof(Dav1dTask) * n_tasks;

            tasks = dav1d_realloc(ALLOC_COMMON_CTX, f->task_thread.tile_tasks[0], size);

            if (!tasks) return -1;

            memset(tasks, 0, size);

            f->task_thread.tile_tasks[0] = tasks;

            f->task_thread.num_tile_tasks = n_tasks;

        }

        f->task_thread.tile_tasks[1] = tasks + n_tasks_per_pass;

    }

    assert(n_tasks <= f->task_thread.num_tile_tasks);

    Dav1dTask *pf_t;

    if (create_filter_sbrow(f, pass, &pf_t))

        return -1;

    Dav1dTask *const p1_tasks = f->task_thread.tile_tasks[1];

    Dav1dTask *prev_t = NULL;

    if (pass == 2) {

        prev_t = &p1_tasks[n_tasks_per_pass - 1];

        // PF task is scheduled after the last sby=0 TILE task

        if (f->frame_hdr->tiling.rows == 1)

            prev_t = prev_t->next;

    }

    tasks += (pass & 1) * n_tasks_per_pass;

    for (int tile_idx = 0; tile_idx < n_tasks_per_pass; tile_idx++) {

        Dav1dTileState *const ts = &f->ts[tile_idx];

        Dav1dTask *t = &tasks[tile_idx];

        t->sby = ts->tiling.row_start >> f->sb_shift;

        if (pf_t && t->sby) {

            prev_t->next = pf_t;

            prev_t = pf_t;

            pf_t = NULL;

        }

        t->recon_progress = 0;

        t->deblock_progress = 0;

        t->deps_skip = 0;

        t->type = pass != 1 ? DAV1D_TASK_TYPE_TILE_RECONSTRUCTION :

                              DAV1D_TASK_TYPE_TILE_ENTROPY;

        t->frame_idx = (int)(f - f->c->fc);

        if (prev_t) prev_t->next = t;

        prev_t = t;

    }

    if (pf_t) {

        prev_t->next = pf_t;

        prev_t = pf_t;

    }

    prev_t->next = NULL;

    atomic_store(&f->task_thread.done[pass & 1], 0);

    // XXX in theory this could be done locklessly, at this point they are no

    // tasks in the frameQ, so no other runner should be using this lock, but

    // we must add both passes at once

    if (!(pass & 1)) {

        pthread_mutex_lock(&f->task_thread.pending_tasks.lock);

        assert(f->task_thread.pending_tasks.head == NULL);

        f->task_thread.pending_tasks.head = f->task_thread.tile_tasks[pass == 2];

        f->task_thread.pending_tasks.tail = prev_t;

        atomic_store(&f->task_thread.pending_tasks.merge, 1);

        atomic_store(&f->task_thread.init_done, 1);

        pthread_mutex_unlock(&f->task_thread.pending_tasks.lock);

    }

    return 0;

}

void dav1d_task_frame_init(Dav1dFrameContext *const f) {

    const Dav1dContext *const c = f->c;

    atomic_store(&f->task_thread.init_done, 0);

    // schedule init task, which will schedule the remaining tasks

    Dav1dTask *const t = &f->task_thread.init_task;

    t->type = DAV1D_TASK_TYPE_INIT;

    t->frame_idx = (int)(f - c->fc);

    t->sby = 0;

    t->recon_progress = t->deblock_progress = 0;

    insert_task(f, t, 1);

}

void dav1d_task_delayed_fg(Dav1dContext *const c, Dav1dPicture *const out,

                           const Dav1dPicture *const in)

{

    struct TaskThreadData *const ttd = &c->task_thread;

    ttd->delayed_fg.in = in;

    ttd->delayed_fg.out = out;

    ttd->delayed_fg.type = DAV1D_TASK_TYPE_FG_PREP;

    atomic_init(&ttd->delayed_fg.progress[0], 0);

    atomic_init(&ttd->delayed_fg.progress[1], 0);

    pthread_mutex_lock(&ttd->lock);

    ttd->delayed_fg.exec = 1;

    ttd->delayed_fg.finished = 0;

    pthread_cond_signal(&ttd->cond);

    do {

        pthread_cond_wait(&ttd->delayed_fg.cond, &ttd->lock);

    } while (!ttd->delayed_fg.finished);

    pthread_mutex_unlock(&ttd->lock);

}

static inline int ensure_progress(struct TaskThreadData *const ttd,

                                  Dav1dFrameContext *const f,

                                  Dav1dTask *const t, const enum TaskType type,

                                  atomic_int *const state, int *const target)

{

    // deblock_rows (non-LR portion) depends on deblock of previous sbrow,

    // so ensure that completed. if not, re-add to task-queue; else, fall-through

    int p1 = atomic_load(state);

    if (p1 < t->sby) {

        t->type = type;

        t->recon_progress = t->deblock_progress = 0;

        *target = t->sby;

        add_pending(f, t);

        pthread_mutex_lock(&ttd->lock);

        return 1;

    }

    return 0;

}

static inline int check_tile(Dav1dTask *const t, Dav1dFrameContext *const f,

                             const int frame_mt)

{

    const int tp = t->type == DAV1D_TASK_TYPE_TILE_ENTROPY;

    const int tile_idx = (int)(t - f->task_thread.tile_tasks[tp]);

    Dav1dTileState *const ts = &f->ts[tile_idx];

    const int p1 = atomic_load(&ts->progress[tp]);

    if (p1 < t->sby) return 1;

    int error = p1 == TILE_ERROR;

    error |= atomic_fetch_or(&f->task_thread.error, error);

    if (!error && frame_mt && !tp) {

        const int p2 = atomic_load(&ts->progress[1]);

        if (p2 <= t->sby) return 1;

        error = p2 == TILE_ERROR;

        error |= atomic_fetch_or(&f->task_thread.error, error);

    }

    if (!error && frame_mt && !IS_KEY_OR_INTRA(f->frame_hdr)) {

        // check reference state

        const Dav1dThreadPicture *p = &f->sr_cur;

        const int ss_ver = p->p.p.layout == DAV1D_PIXEL_LAYOUT_I420;

        const unsigned p_b = (t->sby + 1) << (f->sb_shift + 2);

        const int tile_sby = t->sby - (ts->tiling.row_start >> f->sb_shift);

        const int (*const lowest_px)[2] = ts->lowest_pixel[tile_sby];

        for (int n = t->deps_skip; n < 7; n++, t->deps_skip++) {

            unsigned lowest;

            if (tp) {

                // if temporal mv refs are disabled, we only need this

                // for the primary ref; if segmentation is disabled, we

                // don't even need that

                lowest = p_b;

            } else {

                // +8 is postfilter-induced delay

                const int y = lowest_px[n][0] == INT_MIN ? INT_MIN :

                              lowest_px[n][0] + 8;

                const int uv = lowest_px[n][1] == INT_MIN ? INT_MIN :

                               lowest_px[n][1] * (1 << ss_ver) + 8;

                const int max = imax(y, uv);

                if (max == INT_MIN) continue;

                lowest = iclip(max, 1, f->refp[n].p.p.h);

            }

            const unsigned p3 = atomic_load(&f->refp[n].progress[!tp]);

            if (p3 < lowest) return 1;

            atomic_fetch_or(&f->task_thread.error, p3 == FRAME_ERROR);

        }

    }

    return 0;

}

static inline int get_frame_progress(const Dav1dContext *const c,

                                     const Dav1dFrameContext *const f)

{

    unsigned frame_prog = c->n_fc > 1 ? atomic_load(&f->sr_cur.progress[1]) : 0;

    if (frame_prog >= FRAME_ERROR)

        return f->sbh - 1;

    int idx = frame_prog >> (f->sb_shift + 7);

    int prog;

    do {

        atomic_uint *state = &f->frame_thread.frame_progress[idx];

        const unsigned val = ~atomic_load(state);

        prog = val ? ctz(val) : 32;

        if (prog != 32) break;

        prog = 0;

    } while (++idx < f->frame_thread.prog_sz);

    return ((idx << 5) | prog) - 1;

}

static inline void abort_frame(Dav1dFrameContext *const f, const int error) {

    atomic_store(&f->task_thread.error, error == DAV1D_ERR(EINVAL) ? 1 : -1);

    atomic_store(&f->task_thread.task_counter, 0);

    atomic_store(&f->task_thread.done[0], 1);

    atomic_store(&f->task_thread.done[1], 1);

    atomic_store(&f->sr_cur.progress[0], FRAME_ERROR);

    atomic_store(&f->sr_cur.progress[1], FRAME_ERROR);

    dav1d_decode_frame_exit(f, error);

    f->n_tile_data = 0;

    pthread_cond_signal(&f->task_thread.cond);

}

static inline void delayed_fg_task(const Dav1dContext *const c,

                                   struct TaskThreadData *const ttd)

{

    const Dav1dPicture *const in = ttd->delayed_fg.in;

    Dav1dPicture *const out = ttd->delayed_fg.out;

#if CONFIG_16BPC

    int off;

    if (out->p.bpc != 8)

        off = (out->p.bpc >> 1) - 4;

#endif

    switch (ttd->delayed_fg.type) {

    case DAV1D_TASK_TYPE_FG_PREP:

        ttd->delayed_fg.exec = 0;

        if (atomic_load(&ttd->cond_signaled))

            pthread_cond_signal(&ttd->cond);

        pthread_mutex_unlock(&ttd->lock);

        switch (out->p.bpc) {

#if CONFIG_8BPC

        case 8:

            dav1d_prep_grain_8bpc(&c->dsp[0].fg, out, in,

                                  ttd->delayed_fg.scaling_8bpc,

                                  ttd->delayed_fg.grain_lut_8bpc);

            break;

#endif

#if CONFIG_16BPC

        case 10:

        case 12:

            dav1d_prep_grain_16bpc(&c->dsp[off].fg, out, in,

                                   ttd->delayed_fg.scaling_16bpc,

                                   ttd->delayed_fg.grain_lut_16bpc);

            break;

#endif

        default: abort();

        }

        ttd->delayed_fg.type = DAV1D_TASK_TYPE_FG_APPLY;

        pthread_mutex_lock(&ttd->lock);

        ttd->delayed_fg.exec = 1;

        // fall-through

    case DAV1D_TASK_TYPE_FG_APPLY:;

        int row = atomic_fetch_add(&ttd->delayed_fg.progress[0], 1);

        pthread_mutex_unlock(&ttd->lock);

        int progmax = (out->p.h + FG_BLOCK_SIZE - 1) / FG_BLOCK_SIZE;

        while (row < progmax) {

            if (row + 1 < progmax)

                pthread_cond_signal(&ttd->cond);

            else {

                pthread_mutex_lock(&ttd->lock);

                ttd->delayed_fg.exec = 0;

                pthread_mutex_unlock(&ttd->lock);

            }

            switch (out->p.bpc) {

#if CONFIG_8BPC

            case 8:

                dav1d_apply_grain_row_8bpc(&c->dsp[0].fg, out, in,

                                           ttd->delayed_fg.scaling_8bpc,

                                           ttd->delayed_fg.grain_lut_8bpc, row);

                break;

#endif

#if CONFIG_16BPC

            case 10:

            case 12:

                dav1d_apply_grain_row_16bpc(&c->dsp[off].fg, out, in,

                                            ttd->delayed_fg.scaling_16bpc,

                                            ttd->delayed_fg.grain_lut_16bpc, row);

                break;

#endif

            default: abort();

            }

            row = atomic_fetch_add(&ttd->delayed_fg.progress[0], 1);

            atomic_fetch_add(&ttd->delayed_fg.progress[1], 1);

        }

        pthread_mutex_lock(&ttd->lock);

        ttd->delayed_fg.exec = 0;

        int done = atomic_fetch_add(&ttd->delayed_fg.progress[1], 1) + 1;

        progmax = atomic_load(&ttd->delayed_fg.progress[0]);

        // signal for completion only once the last runner reaches this

        if (done >= progmax) {

            ttd->delayed_fg.finished = 1;

            pthread_cond_signal(&ttd->delayed_fg.cond);

        }

        break;

    default: abort();

    }

}

void *dav1d_worker_task(void *data) {

    Dav1dTaskContext *const tc = data;

    const Dav1dContext *const c = tc->c;

    struct TaskThreadData *const ttd = tc->task_thread.ttd;

    dav1d_set_thread_name("dav1d-worker");

    pthread_mutex_lock(&ttd->lock);

    for (;;) {

        if (tc->task_thread.die) break;

        if (atomic_load(c->flush)) goto park;

        merge_pending(c);

        if (ttd->delayed_fg.exec) { // run delayed film grain first

            delayed_fg_task(c, ttd);

            continue;

        }

        Dav1dFrameContext *f;

        Dav1dTask *t, *prev_t = NULL;

        if (c->n_fc > 1) { // run init tasks second

            for (unsigned i = 0; i < c->n_fc; i++) {

                const unsigned first = atomic_load(&ttd->first);

                f = &c->fc[(first + i) % c->n_fc];

                if (atomic_load(&f->task_thread.init_done)) continue;

                t = f->task_thread.task_head;

                if (!t) continue;

                if (t->type == DAV1D_TASK_TYPE_INIT) goto found;

                if (t->type == DAV1D_TASK_TYPE_INIT_CDF) {

                    // XXX This can be a simple else, if adding tasks of both

                    // passes at once (in dav1d_task_create_tile_sbrow).

                    // Adding the tasks to the pending Q can result in a

                    // thread merging them before setting init_done.

                    // We will need to set init_done before adding to the

                    // pending Q, so maybe return the tasks, set init_done,

                    // and add to pending Q only then.

                    const int p1 = f->in_cdf.progress ?

                        atomic_load(f->in_cdf.progress) : 1;

                    if (p1) {

                        atomic_fetch_or(&f->task_thread.error, p1 == TILE_ERROR);

                        goto found;

                    }

                }

            }

        }

        while (ttd->cur < c->n_fc) { // run decoding tasks last

            const unsigned first = atomic_load(&ttd->first);

            f = &c->fc[(first + ttd->cur) % c->n_fc];

            merge_pending_frame(f);

            prev_t = f->task_thread.task_cur_prev;

            t = prev_t ? prev_t->next : f->task_thread.task_head;

            while (t) {

                if (t->type == DAV1D_TASK_TYPE_INIT_CDF) goto next;

                else if (t->type == DAV1D_TASK_TYPE_TILE_ENTROPY ||

                         t->type == DAV1D_TASK_TYPE_TILE_RECONSTRUCTION)

                {

                    // if not bottom sbrow of tile, this task will be re-added

                    // after it's finished

                    if (!check_tile(t, f, c->n_fc > 1))

                        goto found;

                } else if (t->recon_progress) {

                    const int p = t->type == DAV1D_TASK_TYPE_ENTROPY_PROGRESS;

                    int error = atomic_load(&f->task_thread.error);

                    assert(!atomic_load(&f->task_thread.done[p]) || error);

                    const int tile_row_base = f->frame_hdr->tiling.cols *

                                              f->frame_thread.next_tile_row[p];

                    if (p) {

                        atomic_int *const prog = &f->frame_thread.entropy_progress;

                        const int p1 = atomic_load(prog);

                        if (p1 < t->sby) goto next;

                        atomic_fetch_or(&f->task_thread.error, p1 == TILE_ERROR);

                    }

                    for (int tc = 0; tc < f->frame_hdr->tiling.cols; tc++) {

                        Dav1dTileState *const ts = &f->ts[tile_row_base + tc];

                        const int p2 = atomic_load(&ts->progress[p]);

                        if (p2 < t->recon_progress) goto next;

                        atomic_fetch_or(&f->task_thread.error, p2 == TILE_ERROR);

                    }

                    if (t->sby + 1 < f->sbh) {

                        // add sby+1 to list to replace this one

                        Dav1dTask *next_t = &t[1];

                        *next_t = *t;

                        next_t->sby++;

                        const int ntr = f->frame_thread.next_tile_row[p] + 1;

                        const int start = f->frame_hdr->tiling.row_start_sb[ntr];

                        if (next_t->sby == start)

                            f->frame_thread.next_tile_row[p] = ntr;

                        next_t->recon_progress = next_t->sby + 1;

                        insert_task(f, next_t, 0);

                    }

                    goto found;

                } else if (t->type == DAV1D_TASK_TYPE_CDEF) {

                    atomic_uint *prog = f->frame_thread.copy_lpf_progress;

                    const int p1 = atomic_load(&prog[(t->sby - 1) >> 5]);

                    if (p1 & (1U << ((t->sby - 1) & 31)))

                        goto found;

                } else {

                    assert(t->deblock_progress);

                    const int p1 = atomic_load(&f->frame_thread.deblock_progress);

                    if (p1 >= t->deblock_progress) {

                        atomic_fetch_or(&f->task_thread.error, p1 == TILE_ERROR);

                        goto found;

                    }

                }

            next:

                prev_t = t;

                t = t->next;

                f->task_thread.task_cur_prev = prev_t;

            }

            ttd->cur++;

        }

        if (reset_task_cur(c, ttd, UINT_MAX)) continue;

        if (merge_pending(c)) continue;

    park:

        tc->task_thread.flushed = 1;

        pthread_cond_signal(&tc->task_thread.td.cond);

        // we want to be woken up next time progress is signaled

        atomic_store(&ttd->cond_signaled, 0);

        pthread_cond_wait(&ttd->cond, &ttd->lock);

        tc->task_thread.flushed = 0;

        reset_task_cur(c, ttd, UINT_MAX);

        continue;

    found:

        // remove t from list

        if (prev_t) prev_t->next = t->next;

        else f->task_thread.task_head = t->next;

        if (!t->next) f->task_thread.task_tail = prev_t;

        if (t->type > DAV1D_TASK_TYPE_INIT_CDF && !f->task_thread.task_head)

            ttd->cur++;

        t->next = NULL;

        // we don't need to check cond_signaled here, since we found a task

        // after the last signal so we want to re-signal the next waiting thread

        // and again won't need to signal after that

        atomic_store(&ttd->cond_signaled, 1);

        pthread_cond_signal(&ttd->cond);

        pthread_mutex_unlock(&ttd->lock);

    found_unlocked:;

        const int flush = atomic_load(c->flush);

        int error = atomic_fetch_or(&f->task_thread.error, flush) | flush;

        // run it

        tc->f = f;

        int sby = t->sby;

        switch (t->type) {

        case DAV1D_TASK_TYPE_INIT: {

            assert(c->n_fc > 1);

            int res = dav1d_decode_frame_init(f);

            int p1 = f->in_cdf.progress ? atomic_load(f->in_cdf.progress) : 1;

            if (res || p1 == TILE_ERROR) {

                pthread_mutex_lock(&ttd->lock);

                abort_frame(f, res ? res : DAV1D_ERR(EINVAL));

                reset_task_cur(c, ttd, t->frame_idx);

            } else {

                t->type = DAV1D_TASK_TYPE_INIT_CDF;

                if (p1) goto found_unlocked;

                add_pending(f, t);

                pthread_mutex_lock(&ttd->lock);

            }

            continue;

        }

        case DAV1D_TASK_TYPE_INIT_CDF: {

            assert(c->n_fc > 1);

            int res = DAV1D_ERR(EINVAL);

            if (!atomic_load(&f->task_thread.error))

                res = dav1d_decode_frame_init_cdf(f);

            if (f->frame_hdr->refresh_context && !f->task_thread.update_set)

                atomic_store(f->out_cdf.progress, res < 0 ? TILE_ERROR : 1);

            for (int p = 1; p <= 2 && !res; p++)

                res = dav1d_task_create_tile_sbrow(f, p, 0);

            pthread_mutex_lock(&ttd->lock);

            if (res) {

                abort_frame(f, DAV1D_ERR(ENOMEM));

                reset_task_cur(c, ttd, t->frame_idx);

                atomic_store(&f->task_thread.init_done, 1);

            }

            continue;

        }

        case DAV1D_TASK_TYPE_TILE_ENTROPY:

        case DAV1D_TASK_TYPE_TILE_RECONSTRUCTION: {

            const int p = t->type == DAV1D_TASK_TYPE_TILE_ENTROPY;

            const int tile_idx = (int)(t - f->task_thread.tile_tasks[p]);

            Dav1dTileState *const ts = &f->ts[tile_idx];

            tc->ts = ts;

            tc->by = sby << f->sb_shift;

            const int uses_2pass = c->n_fc > 1;

            tc->frame_thread.pass = !uses_2pass ? 0 :

                1 + (t->type == DAV1D_TASK_TYPE_TILE_RECONSTRUCTION);

            if (!error) error = dav1d_decode_tile_sbrow(tc);

            const int progress = error ? TILE_ERROR : 1 + sby;

            // signal progress

            atomic_fetch_or(&f->task_thread.error, error);

            if (((sby + 1) << f->sb_shift) < ts->tiling.row_end) {

                t->sby++;

                t->deps_skip = 0;

                if (!check_tile(t, f, uses_2pass)) {

                    atomic_store(&ts->progress[p], progress);

                    reset_task_cur_async(ttd, t->frame_idx, c->n_fc);

                    if (!atomic_fetch_or(&ttd->cond_signaled, 1))

                        pthread_cond_signal(&ttd->cond);

                    goto found_unlocked;

                }

                atomic_store(&ts->progress[p], progress);

                add_pending(f, t);

                pthread_mutex_lock(&ttd->lock);

            } else {

                pthread_mutex_lock(&ttd->lock);

                atomic_store(&ts->progress[p], progress);

                reset_task_cur(c, ttd, t->frame_idx);

                error = atomic_load(&f->task_thread.error);

                if (f->frame_hdr->refresh_context &&

                    tc->frame_thread.pass <= 1 && f->task_thread.update_set &&

                    f->frame_hdr->tiling.update == tile_idx)

                {

                    if (!error)

                        dav1d_cdf_thread_update(f->frame_hdr, f->out_cdf.data.cdf,

                                                &f->ts[f->frame_hdr->tiling.update].cdf);

                    if (c->n_fc > 1)

                        atomic_store(f->out_cdf.progress, error ? TILE_ERROR : 1);

                }

                if (atomic_fetch_sub(&f->task_thread.task_counter, 1) - 1 == 0 &&

                    atomic_load(&f->task_thread.done[0]) &&

                    (!uses_2pass || atomic_load(&f->task_thread.done[1])))

                {

                    error = atomic_load(&f->task_thread.error);

                    dav1d_decode_frame_exit(f, error == 1 ? DAV1D_ERR(EINVAL) :

                                            error ? DAV1D_ERR(ENOMEM) : 0);

                    f->n_tile_data = 0;

                    pthread_cond_signal(&f->task_thread.cond);

                }

                assert(atomic_load(&f->task_thread.task_counter) >= 0);

                if (!atomic_fetch_or(&ttd->cond_signaled, 1))

                    pthread_cond_signal(&ttd->cond);

            }

            continue;

        }

        case DAV1D_TASK_TYPE_DEBLOCK_COLS:

            if (!atomic_load(&f->task_thread.error))

                f->bd_fn.filter_sbrow_deblock_cols(f, sby);

            if (ensure_progress(ttd, f, t, DAV1D_TASK_TYPE_DEBLOCK_ROWS,

                                &f->frame_thread.deblock_progress,

                                &t->deblock_progress)) continue;

            // fall-through

        case DAV1D_TASK_TYPE_DEBLOCK_ROWS:

            if (!atomic_load(&f->task_thread.error))

                f->bd_fn.filter_sbrow_deblock_rows(f, sby);

            // signal deblock progress

            if (f->frame_hdr->loopfilter.level_y[0] ||

                f->frame_hdr->loopfilter.level_y[1])

            {

                error = atomic_load(&f->task_thread.error);

                atomic_store(&f->frame_thread.deblock_progress,

                             error ? TILE_ERROR : sby + 1);

                reset_task_cur_async(ttd, t->frame_idx, c->n_fc);

                if (!atomic_fetch_or(&ttd->cond_signaled, 1))

                    pthread_cond_signal(&ttd->cond);

            } else if (f->seq_hdr->cdef || f->lf.restore_planes) {

                atomic_fetch_or(&f->frame_thread.copy_lpf_progress[sby >> 5],

                                1U << (sby & 31));

                // CDEF needs the top buffer to be saved by lr_copy_lpf of the

                // previous sbrow

                if (sby) {

                    int prog = atomic_load(&f->frame_thread.copy_lpf_progress[(sby - 1) >> 5]);

                    if (~prog & (1U << ((sby - 1) & 31))) {

                        t->type = DAV1D_TASK_TYPE_CDEF;

                        t->recon_progress = t->deblock_progress = 0;

                        add_pending(f, t);

                        pthread_mutex_lock(&ttd->lock);

                        continue;

                    }

                }

            }

            // fall-through

        case DAV1D_TASK_TYPE_CDEF:

            if (f->seq_hdr->cdef) {

                if (!atomic_load(&f->task_thread.error))

                    f->bd_fn.filter_sbrow_cdef(tc, sby);

                reset_task_cur_async(ttd, t->frame_idx, c->n_fc);

                if (!atomic_fetch_or(&ttd->cond_signaled, 1))

                    pthread_cond_signal(&ttd->cond);

            }

            // fall-through

        case DAV1D_TASK_TYPE_SUPER_RESOLUTION:

            if (f->frame_hdr->width[0] != f->frame_hdr->width[1])

                if (!atomic_load(&f->task_thread.error))

                    f->bd_fn.filter_sbrow_resize(f, sby);

            // fall-through

        case DAV1D_TASK_TYPE_LOOP_RESTORATION:

            if (!atomic_load(&f->task_thread.error) && f->lf.restore_planes)

                f->bd_fn.filter_sbrow_lr(f, sby);

            // fall-through

        case DAV1D_TASK_TYPE_RECONSTRUCTION_PROGRESS:

            // dummy to cover for no post-filters

        case DAV1D_TASK_TYPE_ENTROPY_PROGRESS:

            // dummy to convert tile progress to frame

            break;

        default: abort();

        }

        // if task completed [typically LR], signal picture progress as per below

        const int uses_2pass = c->n_fc > 1;

        const int sbh = f->sbh;

        const int sbsz = f->sb_step * 4;

        if (t->type == DAV1D_TASK_TYPE_ENTROPY_PROGRESS) {

            error = atomic_load(&f->task_thread.error);

            const unsigned y = sby + 1 == sbh ? UINT_MAX : (unsigned)(sby + 1) * sbsz;

            assert(c->n_fc > 1);

            if (f->sr_cur.p.data[0] /* upon flush, this can be free'ed already */)

                atomic_store(&f->sr_cur.progress[0], error ? FRAME_ERROR : y);

            atomic_store(&f->frame_thread.entropy_progress,

                         error ? TILE_ERROR : sby + 1);

            if (sby + 1 == sbh)

                atomic_store(&f->task_thread.done[1], 1);

            pthread_mutex_lock(&ttd->lock);

            const int num_tasks = atomic_fetch_sub(&f->task_thread.task_counter, 1) - 1;

            if (sby + 1 < sbh && num_tasks) {

                reset_task_cur(c, ttd, t->frame_idx);

                continue;

            }

            if (!num_tasks && atomic_load(&f->task_thread.done[0]) &&

                atomic_load(&f->task_thread.done[1]))

            {

                error = atomic_load(&f->task_thread.error);

                dav1d_decode_frame_exit(f, error == 1 ? DAV1D_ERR(EINVAL) :

                                        error ? DAV1D_ERR(ENOMEM) : 0);

                f->n_tile_data = 0;

                pthread_cond_signal(&f->task_thread.cond);

            }

            reset_task_cur(c, ttd, t->frame_idx);

            continue;

        }

    // t->type != DAV1D_TASK_TYPE_ENTROPY_PROGRESS

        atomic_fetch_or(&f->frame_thread.frame_progress[sby >> 5],

                        1U << (sby & 31));

        pthread_mutex_lock(&f->task_thread.lock);

        sby = get_frame_progress(c, f);

        error = atomic_load(&f->task_thread.error);

        const unsigned y = sby + 1 == sbh ? UINT_MAX : (unsigned)(sby + 1) * sbsz;

        if (c->n_fc > 1 && f->sr_cur.p.data[0] /* upon flush, this can be free'ed already */)

            atomic_store(&f->sr_cur.progress[1], error ? FRAME_ERROR : y);

        pthread_mutex_unlock(&f->task_thread.lock);

        if (sby + 1 == sbh)

            atomic_store(&f->task_thread.done[0], 1);

        pthread_mutex_lock(&ttd->lock);

        const int num_tasks = atomic_fetch_sub(&f->task_thread.task_counter, 1) - 1;

        if (sby + 1 < sbh && num_tasks) {

            reset_task_cur(c, ttd, t->frame_idx);

            continue;

        }

        if (!num_tasks && atomic_load(&f->task_thread.done[0]) &&

            (!uses_2pass || atomic_load(&f->task_thread.done[1])))

        {

            error = atomic_load(&f->task_thread.error);

            dav1d_decode_frame_exit(f, error == 1 ? DAV1D_ERR(EINVAL) :

                                    error ? DAV1D_ERR(ENOMEM) : 0);

            f->n_tile_data = 0;

            pthread_cond_signal(&f->task_thread.cond);

        }

        reset_task_cur(c, ttd, t->frame_idx);

    }

    pthread_mutex_unlock(&ttd->lock);

    return NULL;

}