path: root/gs/base/gxclthrd.c

/* Copyright (C) 2001-2006 Artifex Software, Inc.
   All Rights Reserved.

   This software is provided AS-IS with no warranty, either express or
   implied.

   This software is distributed under license and may not be copied, modified
   or distributed except as expressly authorized under the terms of that
   license.  Refer to licensing information at http://www.artifex.com/
   or contact Artifex Software, Inc.,  7 Mt. Lassen Drive - Suite A-134,
   San Rafael, CA  94903, U.S.A., +1(415)492-9861, for further information.
*/

/* $Id$ */
/* Command list - Support for multiple rendering threads */
#include "memory_.h"
#include "gx.h"
#include "gp.h"
#include "gpcheck.h"
#include "gxsync.h"
#include "gserrors.h"
#include "gxdevice.h"
#include "gsdevice.h"
#include "gxdevmem.h"           /* must precede gxcldev.h */
#include "gdevprn.h"            /* must precede gxcldev.h */
#include "gxcldev.h"
#include "gxgetbit.h"
#include "gdevplnx.h"
#include "gsmemory.h"
#include "gsmchunk.h"
#include "gsmemlok.h"
#include "gxclthrd.h"
#include "gdevdevn.h"
#include "gsicc_cache.h"

/* Forward reference prototypes */
static int clist_start_render_thread(gx_device *dev, int thread_index, int band);
static void clist_render_thread(void *param);

/* Set up and start the render threads */
static int
clist_setup_render_threads(gx_device *dev, int y)
{
    gx_device_printer *pdev = (gx_device_printer *)dev;
    gx_device_clist *cldev = (gx_device_clist *)dev;
    gx_device_clist_common *cdev = (gx_device_clist_common *)cldev;
    gx_device_clist_reader *crdev = &cldev->reader;
    gs_memory_t *mem = cdev->bandlist_memory;
    gs_memory_t *chunk_base_mem = mem->thread_safe_memory;
    gs_memory_status_t mem_status;
    gx_device *protodev;
    gs_c_param_list paramlist;
    int i, code, band;
    int band_count = cdev->nbands;
    char fmode[4];
    gs_devn_params *pclist_devn_params;
    crdev->num_render_threads = pdev->num_render_threads_requested;

    if(gs_debug[':'] != 0)
        dprintf1("%% %d rendering threads requested.\n", pdev->num_render_threads_requested);

    if (crdev->num_render_threads > band_count)
        crdev->num_render_threads = band_count; /* don't bother starting more threads than bands */

    /* Allocate and initialize an array of thread control structures */
    crdev->render_threads = (clist_render_thread_control_t *)
              gs_alloc_byte_array(mem, crdev->num_render_threads,
              sizeof(clist_render_thread_control_t), "clist_setup_render_threads" );
    /* fallback to non-threaded if allocation fails */
    if (crdev->render_threads == NULL) {
        emprintf(mem, " VMerror prevented threads from starting.\n");
        return_error(gs_error_VMerror);
    }

    memset(crdev->render_threads, 0, crdev->num_render_threads *
            sizeof(clist_render_thread_control_t));
    crdev->main_thread_data = cdev->data;               /* save data area */
    /* Based on the line number requested, decide the order of band rendering */
    /* Almost all devices go in increasing line order (except the bmp* devices ) */
    crdev->thread_lookahead_direction = (y < (cdev->height - 1)) ? 1 : -1;
    band = y / crdev->page_info.band_params.BandHeight;

    /* Close the files so we can open them in multiple threads */
    if ((code = cdev->page_info.io_procs->fclose(cdev->page_cfile, cdev->page_cfname, false)) < 0 ||
        (code = cdev->page_info.io_procs->fclose(cdev->page_bfile, cdev->page_bfname, false)) < 0) {
        gs_free_object(mem, crdev->render_threads, "clist_setup_render_threads");
        crdev->render_threads = NULL;
        emprintf(mem, "Closing clist files prevented threads from starting.\n");
        return_error(gs_error_unknownerror); /* shouldn't happen */
    }
    cdev->page_cfile = cdev->page_bfile = NULL;
    strcpy(fmode, "r");                 /* read access for threads */
    strncat(fmode, gp_fmode_binary_suffix, 1);
    /* Find the prototype for this device (needed so we can copy from it) */
    for (i=0; (protodev = (gx_device *)gs_getdevice(i)) != NULL; i++)
        if (strcmp(protodev->dname, dev->dname) == 0)
            break;
    if (protodev == NULL) {
        emprintf(mem,
                 "Could not find prototype device. Rendering threads not started.\n");
        return gs_error_rangecheck;
    }

    gs_c_param_list_write(&paramlist, mem);
    if ((code = gs_getdeviceparams(dev, (gs_param_list *)&paramlist)) < 0) {
        emprintf1(mem,
                  "Error getting device params, code=%d. Rendering threads not started.\n",
                  code);
        return code;
    }

    /* If the 'mem' is not thread safe, we need to wrap it in a locking memory */
    gs_memory_status(chunk_base_mem, &mem_status);
    if (mem_status.is_thread_safe == false) {
            return_error(gs_error_VMerror);
    }

    /* Loop creating the devices and semaphores for each thread, then start them */
    for (i=0; (i < crdev->num_render_threads) && (band >= 0) && (band < band_count);
            i++, band += crdev->thread_lookahead_direction) {
        gx_device *ndev;
        gx_device_clist *ncldev;
        gx_device_clist_common *ncdev;
        clist_render_thread_control_t *thread = &(crdev->render_threads[i]);

        /* Every thread will have a 'chunk allocator' to reduce the interaction
         * with the 'base' allocator which has 'mutex' (locking) protection.
         * This improves performance of the threads.
         */
        if ((code = gs_memory_chunk_wrap(&(thread->memory), chunk_base_mem )) < 0) {
            emprintf1(mem, "chunk_wrap returned error code: %d\n", code);
            break;
        }

        thread->band = -1;              /* a value that won't match any valid band */
        if ((code = gs_copydevice((gx_device **) &ndev, protodev, thread->memory)) < 0) {
            code = 0;           /* even though we failed, no cleanup needed */
            break;
        }
        ncldev = (gx_device_clist *)ndev;
        ncdev = (gx_device_clist_common *)ndev;
        gx_device_fill_in_procs(ndev);
        ((gx_device_printer *)ncdev)->buffer_memory = ncdev->memory =
                ncdev->bandlist_memory = thread->memory;
        gs_c_param_list_read(&paramlist);
        ndev->PageCount = dev->PageCount;       /* copy to prevent mismatch error */
#if CMM_THREAD_SAFE
        ndev->icc_struct = dev->icc_struct;  /* Set before put params */
        rc_increment(ndev->icc_struct);
#endif
        if ((code = gs_putdeviceparams(ndev, (gs_param_list *)&paramlist)) < 0)
            break;
        /* In the case of a separation device, we need to make sure we get the
           devn params copied over */
        pclist_devn_params = dev_proc(dev, ret_devn_params)(dev);
        if (pclist_devn_params != NULL) {
            code = devn_copy_params(dev, (gx_device*) ncdev);
            if (code < 0) return_error(gs_error_VMerror);
        }
        ncdev->page_uses_transparency = cdev->page_uses_transparency;
        if_debug3(gs_debug_flag_icc,"[icc] MT clist device = 0x%x profile = 0x%x handle = 0x%x\n", 
                  ncdev,
                  ncdev->icc_struct->device_profile[0],
                  ncdev->icc_struct->device_profile[0]->profile_handle);
        /* gdev_prn_allocate_memory sets the clist for writing, creating new files.
         * We need  to unlink those files and open the main thread's files, then
         * reset the clist state for reading/rendering
         */
        if ((code = gdev_prn_allocate_memory(ndev, NULL, ndev->width, ndev->height)) < 0)
            break;
        /* Needed for case when the target has cielab profile and pdf14 device
           has a RGB profile stored in the profile list of the clist */
        ncdev->trans_dev_icc_hash = cdev->trans_dev_icc_hash;
        thread->cdev = ndev;
        /* close and unlink the temp files just created */
        cdev->page_info.io_procs->fclose(ncdev->page_cfile, ncdev->page_cfname, true);
        cdev->page_info.io_procs->fclose(ncdev->page_bfile, ncdev->page_bfname, true);
        /* open the main thread's files for this thread */
        if ((code=cdev->page_info.io_procs->fopen(cdev->page_cfname, fmode, &ncdev->page_cfile,
                            thread->memory, thread->memory, true)) < 0 ||
             (code=cdev->page_info.io_procs->fopen(cdev->page_bfname, fmode, &ncdev->page_bfile,
                            thread->memory, thread->memory, false)) < 0)
            break;
        clist_render_init(ncldev);      /* Initialize clist device for reading */
        ncdev->page_bfile_end_pos = cdev->page_bfile_end_pos;
        /* Use the same link cache in each thread and the same profile table.
           The threads are maintained until clist_finish_page.  At which
           point, the threads are torn down and the master clist reader device
           is destroyed along with the icc_table and the icc_cache_cl */
#if CMM_THREAD_SAFE
        ncdev->icc_cache_cl = cdev->icc_cache_cl;
#else
        ncdev->icc_cache_cl = gsicc_cache_new(crdev->memory);
#endif
        ncdev->icc_table = cdev->icc_table;
        /* create the buf device for this thread, and allocate the semaphores */
        if ((code = gdev_create_buf_device(cdev->buf_procs.create_buf_device,
                                &(thread->bdev), cdev->target,
                                band*crdev->page_band_height, NULL,
                                thread->memory, clist_get_band_complexity(dev,y)) < 0))
            break;
        if ((thread->sema_this = gx_semaphore_alloc(thread->memory)) == NULL ||
            (thread->sema_group = gx_semaphore_alloc(thread->memory)) == NULL) {
            code = gs_error_VMerror;
            break;
        }
        /* Start thread 'i' to do band */
        if ((code = clist_start_render_thread(dev, i, band)) < 0)
            break;
    }
    gs_c_param_list_release(&paramlist);
    /* If the code < 0, the last thread creation failed -- clean it up */
    if (code < 0) {
        /* the following relies on 'free' ignoring NULL pointers */
        gx_semaphore_free(crdev->render_threads[i].sema_group);
        gx_semaphore_free(crdev->render_threads[i].sema_this);
        if (crdev->render_threads[i].bdev != NULL)
            cdev->buf_procs.destroy_buf_device(crdev->render_threads[i].bdev);
        if (crdev->render_threads[i].cdev != NULL) {
            gx_device_clist_common *thread_cdev = (gx_device_clist_common *)crdev->render_threads[i].cdev;

            /* Close the file handles, but don't delete (unlink) the files */
            thread_cdev->page_info.io_procs->fclose(thread_cdev->page_bfile, thread_cdev->page_bfname, false);
            thread_cdev->page_info.io_procs->fclose(thread_cdev->page_cfile, thread_cdev->page_cfname, false);
            thread_cdev->do_not_open_or_close_bandfiles = true; /* we already closed the files */

            gdev_prn_free_memory((gx_device *)thread_cdev);
            gs_free_object(crdev->render_threads[i].memory, thread_cdev,
            "clist_setup_render_threads");
        }
        if (crdev->render_threads[i].memory != NULL)
            gs_memory_chunk_release(crdev->render_threads[i].memory);
    }
    /* If we weren't able to create at least one thread, punt   */
    /* Although a single thread isn't any more efficient, the   */
    /* machinery still works, so that's OK.                     */
    if (i == 0) {
        if (crdev->render_threads[0].memory != NULL) {
            gs_memory_chunk_release(crdev->render_threads[0].memory);
            /* free up the locking wrapper if we allocated one */
            if (chunk_base_mem != mem) {
                gs_memory_locked_release((gs_memory_locked_t *)chunk_base_mem);
                gs_free_object(mem, chunk_base_mem, "clist_setup_render_threads(locked allocator)");
            }
        }
        gs_free_object(mem, crdev->render_threads, "clist_setup_render_threads");
        crdev->render_threads = NULL;
        /* restore the file pointers */
        if (cdev->page_cfile == NULL) {
            char fmode[4];

            strcpy(fmode, "a+");        /* file already exists and we want to re-use it */
            strncat(fmode, gp_fmode_binary_suffix, 1);
            cdev->page_info.io_procs->fopen(cdev->page_cfname, fmode, &cdev->page_cfile,
                                mem, cdev->bandlist_memory, true);
            cdev->page_info.io_procs->fseek(cdev->page_cfile, 0, SEEK_SET, cdev->page_cfname);
            cdev->page_info.io_procs->fopen(cdev->page_bfname, fmode, &cdev->page_bfile,
                                mem, cdev->bandlist_memory, false);
            cdev->page_info.io_procs->fseek(cdev->page_bfile, 0, SEEK_SET, cdev->page_bfname);
        }
        emprintf1(mem, "Rendering threads not started, code=%d.\n", code);
        return_error(code);
    }
    crdev->num_render_threads = i;
    crdev->curr_render_thread = 0;

    if(gs_debug[':'] != 0)
        dprintf1("%% Using %d rendering threads\n", i);

    return 0;
}

void
clist_teardown_render_threads(gx_device *dev)
{
    gx_device_clist *cldev = (gx_device_clist *)dev;
    gx_device_clist_common *cdev = (gx_device_clist_common *)dev;
    gx_device_clist_reader *crdev = &cldev->reader;
    gs_memory_t *mem = cdev->bandlist_memory, *chunk_base_mem;
    int i;

    if (crdev->render_threads != NULL) {

        chunk_base_mem = gs_memory_chunk_target(crdev->render_threads[0].memory);
        /* Wait for each thread to finish then free its memory */
        for (i = (crdev->num_render_threads - 1); i >= 0; i--) {
            clist_render_thread_control_t *thread = &(crdev->render_threads[i]);
            gx_device_clist_common *thread_cdev = (gx_device_clist_common *)thread->cdev;

            if (thread->status == RENDER_THREAD_BUSY)
                gx_semaphore_wait(thread->sema_this);
            gp_thread_finish(thread->thread);
            thread->thread = NULL;
            /* Free control semaphores */
            gx_semaphore_free(thread->sema_group);
            gx_semaphore_free(thread->sema_this);
            /* destroy the thread's buffer device */
            thread_cdev->buf_procs.destroy_buf_device(thread->bdev);
            /*
             * Free the BufferSpace, close the band files
             * Note that the BufferSpace is freed using 'ppdev->buf' so the 'data'
             * pointer doesn't need to be the one that the thread started with
             */
            /* Close the file handles, but don't delete (unlink) the files */
            thread_cdev->page_info.io_procs->fclose(thread_cdev->page_bfile, thread_cdev->page_bfname, false);
            thread_cdev->page_info.io_procs->fclose(thread_cdev->page_cfile, thread_cdev->page_cfname, false);
            thread_cdev->do_not_open_or_close_bandfiles = true; /* we already closed the files */
            gdev_prn_free_memory((gx_device *)thread_cdev);
            /* Free the device copy this thread used.  Note that the
               deviceN stuff if was allocated and copied earlier for the device
               will be freed with this call and the icc_struct ref count will be decremented. */
            gs_free_object(thread->memory, thread_cdev, "clist_teardown_render_threads");
#ifdef DEBUG
            if (gs_debug[':'])
                dprintf2("%% Thread %d total usertime=%ld msec\n", i, thread->cputime);
            dprintf1("\nthread: %d ending memory state...\n", i);
            gs_memory_chunk_dump_memory(thread->memory);
            dprintf("                                    memory dump done.\n");
#endif

            gs_memory_chunk_release(thread->memory);
        }
        cdev->data = crdev->main_thread_data;   /* restore the pointer for writing */
        gs_free_object(mem, crdev->render_threads, "clist_teardown_render_threads");
        crdev->render_threads = NULL;

        /* Now re-open the clist temp files so we can write to them */
        if (cdev->page_cfile == NULL) {
            char fmode[4];

            strcpy(fmode, "a+");        /* file already exists and we want to re-use it */
            strncat(fmode, gp_fmode_binary_suffix, 1);
            cdev->page_info.io_procs->fopen(cdev->page_cfname, fmode, &cdev->page_cfile,
                                mem, cdev->bandlist_memory, true);
            cdev->page_info.io_procs->fseek(cdev->page_cfile, 0, SEEK_SET, cdev->page_cfname);
            cdev->page_info.io_procs->fopen(cdev->page_bfname, fmode, &cdev->page_bfile,
                                mem, cdev->bandlist_memory, false);
            cdev->page_info.io_procs->fseek(cdev->page_bfile, 0, SEEK_SET, cdev->page_bfname);
        }
    }
}

static int
clist_start_render_thread(gx_device *dev, int thread_index, int band)
{
    gx_device_clist *cldev = (gx_device_clist *)dev;
    gx_device_clist_reader *crdev = &cldev->reader;
    int code;

    crdev->render_threads[thread_index].band = band;
    crdev->render_threads[thread_index].status = RENDER_THREAD_BUSY;

    /* Finally, fire it up */
    code = gp_thread_start(clist_render_thread,
                           &(crdev->render_threads[thread_index]),
                           &(crdev->render_threads[thread_index].thread));

    return code;
}

static void
clist_render_thread(void *data)
{
    clist_render_thread_control_t *thread = (clist_render_thread_control_t *)data;
    gx_device *dev = thread->cdev;
    gx_device_clist *cldev = (gx_device_clist *)dev;
    gx_device_clist_reader *crdev = &cldev->reader;
    gx_device *bdev = thread->bdev;
    gs_int_rect band_rect;
    byte *mdata = crdev->data + crdev->page_tile_cache_size;
    uint raster = bitmap_raster(dev->width * dev->color_info.depth);
    int code;
    int band_height = crdev->page_band_height;
    int band = thread->band;
    int band_begin_line = band * band_height;
    int band_end_line = band_begin_line + band_height;
    int band_num_lines;
#ifdef DEBUG
    long starttime[2], endtime[2];

    gp_get_usertime(starttime); /* thread start time */
#endif
    if (band_end_line > dev->height)
        band_end_line = dev->height;
    band_num_lines = band_end_line - band_begin_line;

    code = crdev->buf_procs.setup_buf_device
            (bdev, mdata, raster, NULL, 0, band_num_lines, band_num_lines);
    band_rect.p.x = 0;
    band_rect.p.y = band_begin_line;
    band_rect.q.x = dev->width;
    band_rect.q.y = band_end_line;
    if (code >= 0)
        code = clist_render_rectangle(cldev, &band_rect, bdev, NULL, true);
    /* Reset the band boundaries now */
    crdev->ymin = band_begin_line;
    crdev->ymax = band_end_line;
    crdev->offset_map = NULL;
    if (code < 0)
        thread->status = code;          /* shouldn't happen */
    else
        thread->status = RENDER_THREAD_DONE;    /* OK */

#ifdef DEBUG
    gp_get_usertime(endtime);
    thread->cputime += (endtime[0] - starttime[0]) * 1000 +
             (endtime[1] - starttime[1]) / 1000000;
#endif
    /*
     * Signal the semaphores. We signal the 'group' first since even if
     * the waiter is released on the group, it still needs to check
     * status on the thread
     */
    gx_semaphore_signal(thread->sema_group);
    gx_semaphore_signal(thread->sema_this);
}

/*
 * Copy the raster data from the completed thread to the caller's
 * device (the main thread)
 * Return 0 if OK, < 0 is the error code from the thread
 *
 * After swapping the pointers, start up the completed thread with the
 * next band remaining to do (if any)
 */
static int
clist_get_band_from_thread(gx_device *dev, int band_needed)
{
    gx_device_clist *cldev = (gx_device_clist *)dev;
    gx_device_clist_common *cdev = (gx_device_clist_common *)dev;
    gx_device_clist_reader *crdev = &cldev->reader;
    int i, next_band, code = 0;
    int thread_index = crdev->curr_render_thread;
    clist_render_thread_control_t *thread = &(crdev->render_threads[thread_index]);
    gx_device_clist_common *thread_cdev = (gx_device_clist_common *)thread->cdev;
    int band_height = crdev->page_info.band_params.BandHeight;
    int band_count = cdev->nbands;
    byte *tmp;                  /* for swapping data areas */

    /* We expect that the thread needed will be the 'current' thread */
    if (thread->band != band_needed) {
        int band = band_needed;

        /* Probably we went in the wrong direction, so let the threads */
        /* all complete, then restart them in the opposite direction   */
        /* If the caller is 'bouncing around' we may end up back here, */
        /* but that is a VERY rare case (we haven't seen it yet).      */
        for (i=0; i < crdev->num_render_threads; i++) {
            clist_render_thread_control_t *thread = &(crdev->render_threads[i]);

            if (thread->status == RENDER_THREAD_BUSY)
                gx_semaphore_wait(thread->sema_this);
        }
        crdev->thread_lookahead_direction *= -1;      /* reverse direction (but may be overruled below) */
        if (band_needed == band_count-1)
            crdev->thread_lookahead_direction = -1;   /* assume backwards if we are asking for the last band */
        if (band_needed == 0)
            crdev->thread_lookahead_direction = 1;    /* force forward if we are looking for band 0 */
        /* Loop creating the devices and semaphores for each thread, then start them */
        for (i=0; (i < crdev->num_render_threads) && (band >= 0) && (band < band_count);
                i++, band += crdev->thread_lookahead_direction) {
            thread = &(crdev->render_threads[i]);

            thread->band = -1;          /* a value that won't match any valid band */
            /* Start thread 'i' to do band */
            if ((code = clist_start_render_thread(dev, i, band)) < 0)
                break;
        }
        crdev->curr_render_thread = thread_index = 0;
        thread = &(crdev->render_threads[0]);
    }
    /* Wait for this thread */
    gx_semaphore_wait(thread->sema_this);
    gp_thread_finish(thread->thread);
    thread->thread = NULL;
    if (thread->status < 0)
        return thread->status;          /* FAIL */

    /* Swap the data areas to avoid the copy */
    tmp = cdev->data;
    cdev->data = thread_cdev->data;
    thread_cdev->data = tmp;
    thread->status = RENDER_THREAD_IDLE;        /* the data is no longer valid */
    thread->band = -1;
    /* Update the bounds for this band */
    cdev->ymin =  band_needed * band_height;
    cdev->ymax =  cdev->ymin + band_height;
    if (cdev->ymax > dev->height)
        cdev->ymax = dev->height;

    /* If we are not at the final band, start up this thread with the next one to do */
    next_band = band_needed + (crdev->num_render_threads * crdev->thread_lookahead_direction);
    if (next_band >= 0 && next_band < band_count)
        code = clist_start_render_thread(dev, thread_index, next_band);
    /* bump the 'curr' to the next thread */
    crdev->curr_render_thread = crdev->curr_render_thread == crdev->num_render_threads - 1 ?
                0 : crdev->curr_render_thread + 1;

    return code;
}

/* Copy a rasterized rectangle to the client, rasterizing if needed. */
/* The first invocation starts multiple threads to perform "look ahead" */
/* rendering adjacent to the first band (forward or backward) */
static int
clist_get_bits_rect_mt(gx_device *dev, const gs_int_rect * prect,
                         gs_get_bits_params_t *params, gs_int_rect **unread)
{
    gx_device_printer *pdev = (gx_device_printer *)dev;
    gx_device_clist *cldev = (gx_device_clist *)dev;
    gx_device_clist_common *cdev = (gx_device_clist_common *)dev;
    gx_device_clist_reader *crdev = &cldev->reader;
    gs_memory_t *mem = cdev->bandlist_memory;
    gs_get_bits_options_t options = params->options;
    int y = prect->p.y;
    int end_y = prect->q.y;
    int line_count = end_y - y;
    int band_height = crdev->page_info.band_params.BandHeight;
    int band = y / band_height;
    gs_int_rect band_rect;
    int lines_rasterized;
    gx_device *bdev;
    byte *mdata;
    uint raster = bitmap_raster(dev->width * dev->color_info.depth);
    int my;
    int code = 0;

    /* This page might not want multiple threads */
    /* Also we don't support plane extraction using multiple threads */
    if (pdev->num_render_threads_requested < 1 || (options & GB_SELECT_PLANES))
        return clist_get_bits_rectangle(dev, prect, params, unread);

    if (prect->p.x < 0 || prect->q.x > dev->width ||
        y < 0 || end_y > dev->height
        )
        return_error(gs_error_rangecheck);
    if (line_count <= 0 || prect->p.x >= prect->q.x)
        return 0;

    if (crdev->ymin < 0) {
        if ((code = clist_close_writer_and_init_reader(cldev)) < 0)
            return code;
        if (clist_setup_render_threads(dev, y) < 0)
            /* problem setting up the threads, revert to single threaded */
            return clist_get_bits_rectangle(dev, prect, params, unread);
    }
    else {
        if (crdev->render_threads == NULL) {
            /* If we get here with with ymin >=0, it's because we closed the threads */
            /* while doing a page due to an error. Use single threaded mode.         */
            return clist_get_bits_rectangle(dev, prect, params, unread);
        }
    }
    /* If we already have the band's data, just return it */
    if (y < crdev->ymin || end_y > crdev->ymax)
        code = clist_get_band_from_thread(dev, band);
    if (code < 0)
        goto free_thread_out;
    mdata = crdev->data + crdev->page_tile_cache_size;
    if ((code = gdev_create_buf_device(cdev->buf_procs.create_buf_device,
                                  &bdev, cdev->target, y, NULL,
                                  mem, clist_get_band_complexity(dev,y))) < 0 ||
        (code = crdev->buf_procs.setup_buf_device(bdev, mdata, raster, NULL,
                            y - crdev->ymin, line_count, crdev->ymax - crdev->ymin)) < 0)
        goto free_thread_out;

    lines_rasterized = min(band_height, line_count);
    /* Return as much of the rectangle as falls within the rasterized lines. */
    band_rect = *prect;
    band_rect.p.y = 0;
    band_rect.q.y = lines_rasterized;
    code = dev_proc(bdev, get_bits_rectangle)
        (bdev, &band_rect, params, unread);
    cdev->buf_procs.destroy_buf_device(bdev);
    if (code < 0)
        goto free_thread_out;

    /* Note that if called via 'get_bits', the line count will always be 1 */
    if (lines_rasterized == line_count) {
        return code;
    }

/***** TODO: Handle the below with data from the threads *****/
    /*
     * We'll have to return the rectangle in pieces.  Force GB_RETURN_COPY
     * rather than GB_RETURN_POINTER, and require all subsequent pieces to
     * use the same values as the first piece for all of the other format
     * options.  If copying isn't allowed, or if there are any unread
     * rectangles, punt.
     */
    if (!(options & GB_RETURN_COPY) || code > 0)
        return gx_default_get_bits_rectangle(dev, prect, params, unread);
    options = params->options;
    if (!(options & GB_RETURN_COPY)) {
        /* Redo the first piece with copying. */
        params->options = options =
            (params->options & ~GB_RETURN_ALL) | GB_RETURN_COPY;
        lines_rasterized = 0;
    }
    {
        gs_get_bits_params_t band_params;
        uint raster = gx_device_raster(bdev, true);

        code = gdev_create_buf_device(cdev->buf_procs.create_buf_device,
                                      &bdev, cdev->target, y, NULL,
                                      mem, clist_get_band_complexity(dev, y));
        if (code < 0)
            return code;
        band_params = *params;
        while ((y += lines_rasterized) < end_y) {
            /* Increment data pointer by lines_rasterized. */
            band_params.data[0] += raster * lines_rasterized;
            line_count = end_y - y;
            code = clist_rasterize_lines(dev, y, line_count, bdev, NULL, &my);
            if (code < 0)
                break;
            lines_rasterized = min(code, line_count);
            band_rect.p.y = my;
            band_rect.q.y = my + lines_rasterized;
            code = dev_proc(bdev, get_bits_rectangle)
                (bdev, &band_rect, &band_params, unread);
            if (code < 0)
                break;
            params->options = options = band_params.options;
            if (lines_rasterized == line_count)
                break;
        }
        cdev->buf_procs.destroy_buf_device(bdev);
    }
    return code;

/* Free up thread stuff */
free_thread_out:
    clist_teardown_render_threads(dev);
    return code;
}

static void
test_threads(void *dummy)
{
}

int
clist_enable_multi_thread_render(gx_device *dev)
{
    int code = -1;
    gp_thread_id thread;

    /* We need to test gp_thread_start since we may be on a platform  */
    /* built without working threads, i.e., using gp_nsync.c dummy    */
    /* routines. The nosync gp_thread_start returns a -ve error code. */
    if ((code = gp_thread_start(test_threads, NULL, &thread)) < 0 ) {
        return code;    /* Threads don't work */
    }
    gp_thread_finish(thread);
    set_dev_proc(dev, get_bits_rectangle, clist_get_bits_rect_mt);

    return 1;
}