jobs.c

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/*
    This file is part of darktable,
    Copyright (C) 2009-2010 johannes hanika.
    Copyright (C) 2010 Alexandre Prokoudine.
    Copyright (C) 2010 Henrik Andersson.
    Copyright (C) 2014-2017 Tobias Ellinghaus.
    Copyright (C) 2015-2017 Roman Lebedev.
    Copyright (C) 2020-2021 Hanno Schwalm.
    Copyright (C) 2020 Pascal Obry.
    Copyright (C) 2022, 2025-2026 Aurélien PIERRE.
    Copyright (C) 2022 Martin Bařinka.
    
    darktable is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
    
    darktable is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
    
    You should have received a copy of the GNU General Public License
    along with darktable.  If not, see <http://www.gnu.org/licenses/>.
*/
 
#include "system/sys_resources.h"
#include "control/jobs.h"
#include "control/control.h"
#include "common/times.h"
#include "common/logging.h"
 
#define DT_CONTROL_FG_PRIORITY 4
 
// The thumbtable allows at most 840 thumbs at once.
// Once an order to recompute has been dispatched, thumbnails are not drawn
// until it finishes and we get the final buffer.
// If jobs are flushed from the queue before completion,
// those thumbnails will never be redrawn.
#define DT_CONTROL_MAX_JOBS 840
 
/* the queue can have scheduled jobs but all
    the workers are sleeping, so this kicks the workers
    on timed interval.
*/
typedef struct worker_thread_parameters_t
{
  dt_control_t *self;
  int32_t threadid;
} worker_thread_parameters_t;
 
typedef struct _dt_job_t
{
  dt_job_execute_callback execute;
  void *params;
  size_t params_size;
  dt_job_destroy_callback params_destroy;
  int32_t result;
 
  dt_pthread_mutex_t state_mutex;
  dt_pthread_mutex_t wait_mutex;
 
  dt_job_state_t state;
  unsigned char priority;
  dt_job_queue_t queue;
 
  dt_job_state_change_callback state_changed_cb;
 
  dt_progress_t *progress;
 
  char description[DT_CONTROL_DESCRIPTION_LEN];
} _dt_job_t;
 
static inline int dt_control_job_equal(_dt_job_t *j1, _dt_job_t *j2)
{
  if(IS_NULL_PTR(j1) || IS_NULL_PTR(j2)) return 0;
  if(j1->params_size != 0 && j1->params_size == j2->params_size)
    return (j1->execute == j2->execute && j1->state_changed_cb == j2->state_changed_cb
            && j1->queue == j2->queue && (memcmp(j1->params, j2->params, j1->params_size) == 0));
  return (j1->execute == j2->execute && j1->state_changed_cb == j2->state_changed_cb && j1->queue == j2->queue
          && (g_strcmp0(j1->description, j2->description) == 0));
}
 
static void dt_control_job_set_state(_dt_job_t *job, dt_job_state_t state)
{
  if(IS_NULL_PTR(job)) return;
  dt_pthread_mutex_lock(&job->state_mutex);
  if(state >= DT_JOB_STATE_FINISHED  && job->state != DT_JOB_STATE_RUNNING && job->progress)
  {
    dt_control_progress_destroy(dt_control_get_global(), job->progress);
    job->progress = NULL;
  }
  job->state = state;
  /* pass state change to callback */
  if(job->state_changed_cb) job->state_changed_cb(job, state);
  dt_pthread_mutex_unlock(&job->state_mutex);
}
 
dt_job_state_t dt_control_job_get_state(_dt_job_t *job)
{
  if(IS_NULL_PTR(job)) return DT_JOB_STATE_DISPOSED;
  dt_pthread_mutex_lock(&job->state_mutex);
  dt_job_state_t state = job->state;
  dt_pthread_mutex_unlock(&job->state_mutex);
  return state;
}
 
void dt_control_job_set_params(_dt_job_t *job, void *params, dt_job_destroy_callback callback)
{
  if(IS_NULL_PTR(job) || dt_control_job_get_state(job) != DT_JOB_STATE_INITIALIZED) return;
  job->params = params;
  job->params_size = 0;
  job->params_destroy = callback;
}
 
void dt_control_job_set_params_with_size(dt_job_t *job, void *params, size_t params_size,
                                         dt_job_destroy_callback callback)
{
  if(IS_NULL_PTR(job) || dt_control_job_get_state(job) != DT_JOB_STATE_INITIALIZED) return;
  job->params = params;
  job->params_size = params_size;
  job->params_destroy = callback;
}
 
void *dt_control_job_get_params(const _dt_job_t *job)
{
  if(IS_NULL_PTR(job)) return NULL;
  return job->params;
}
 
dt_job_t *dt_control_job_create(dt_job_execute_callback execute, const char *msg, ...)
{
  _dt_job_t *job = (_dt_job_t *)calloc(1, sizeof(_dt_job_t));
  if(IS_NULL_PTR(job)) return NULL;
 
  va_list ap;
  va_start(ap, msg);
  vsnprintf(job->description, DT_CONTROL_DESCRIPTION_LEN, msg, ap);
  va_end(ap);
 
  job->execute = execute;
  job->state = DT_JOB_STATE_INITIALIZED;
 
  dt_pthread_mutex_init(&job->state_mutex, NULL);
  dt_pthread_mutex_init(&job->wait_mutex, NULL);
  return job;
}
 
void dt_control_job_dispose(_dt_job_t *job)
{
  if(IS_NULL_PTR(job)) return;
  if(job->progress) dt_control_progress_destroy(dt_control_get_global(), job->progress);
  job->progress = NULL;
  dt_control_job_set_state(job, DT_JOB_STATE_DISPOSED);
  if(job->params_destroy) job->params_destroy(job->params);
  dt_pthread_mutex_destroy(&job->state_mutex);
  dt_pthread_mutex_destroy(&job->wait_mutex);
  dt_free(job);
}
 
void dt_control_job_set_state_callback(_dt_job_t *job, dt_job_state_change_callback cb)
{
  // once the job got added to the queue it may not be changed from the outside
  if(dt_control_job_get_state(job) != DT_JOB_STATE_INITIALIZED)
    return; // get_state returns DISPOSED when IS_NULL_PTR(job)
  job->state_changed_cb = cb;
}
 
 
static void dt_control_job_print(_dt_job_t *job)
{
  if(IS_NULL_PTR(job)) return;
  dt_print(DT_DEBUG_CONTROL, "%s | queue: %d | priority: %d", job->description, job->queue, job->priority);
}
 
void dt_control_job_cancel(_dt_job_t *job)
{
  dt_control_job_set_state(job, DT_JOB_STATE_CANCELLED);
}
 
void dt_control_job_wait(_dt_job_t *job)
{
  if(IS_NULL_PTR(job)) return;
  dt_job_state_t state = dt_control_job_get_state(job);
 
  // NOTE: could also use signals.
 
  /* if job execution is not finished let's wait for it */
  if(state == DT_JOB_STATE_RUNNING || state == DT_JOB_STATE_CANCELLED)
  {
    // once the job finishes, it unlocks the mutex
    // so by locking the mutex here, we will only get the lock once the job
    // has finished and unlocked it.
    dt_pthread_mutex_lock(&job->wait_mutex);
    // yay, the job finished, we got the lock. nothing more to do.
    dt_pthread_mutex_unlock(&job->wait_mutex);
  }
}
 
static int32_t dt_control_run_job_res(dt_control_t *control, int32_t res)
{
  if(((unsigned int)res) >= DT_CTL_WORKER_RESERVED) return -1;
 
  _dt_job_t *job = NULL;
  dt_pthread_mutex_lock(&control->res_mutex);
  if(control->new_res[res])
  {
    job = control->job_res[res];
    control->job_res[res] = NULL; // this job belongs to us now, the queue may not touch it any longer
  }
  control->new_res[res] = 0;
  dt_pthread_mutex_unlock(&control->res_mutex);
  if(IS_NULL_PTR(job)) return -1;
 
  /* change state to running */
  dt_pthread_mutex_lock(&job->wait_mutex);
  if(dt_control_job_get_state(job) == DT_JOB_STATE_QUEUED)
  {
    dt_print(DT_DEBUG_CONTROL, "[run_job+] %02d %f ", res, dt_get_wtime());
    dt_control_job_print(job);
    dt_print(DT_DEBUG_CONTROL, "\n");
 
    /* execute job */
    dt_control_job_set_state(job, DT_JOB_STATE_RUNNING);
    job->result = job->execute(job);
 
    dt_control_job_set_state(job, DT_JOB_STATE_FINISHED);
    dt_print(DT_DEBUG_CONTROL, "[run_job-] %02d %f ", res, dt_get_wtime());
    dt_control_job_print(job);
    dt_print(DT_DEBUG_CONTROL, "\n");
  }
  dt_pthread_mutex_unlock(&job->wait_mutex);
  dt_control_job_dispose(job);
  return 0;
}
 
static _dt_job_t *dt_control_schedule_job(dt_control_t *control)
{
  /*
   * job scheduling works like this:
   * - when there is a single job in the queue head with a maximal priority -> pick it
   * - otherwise pick among the ones with the maximal priority in the following order:
   *   * user foreground
   *   * system foreground
   *   * user background
   *   * system background
   * - the jobs that didn't get picked this round get their priority incremented
   */
 
  dt_pthread_mutex_lock(&control->queue_mutex);
 
  // find the job
  _dt_job_t *job = NULL;
  int winner_queue = DT_JOB_QUEUE_MAX;
  int max_priority = -1;
  for(int i = 0; i < DT_JOB_QUEUE_MAX; i++)
  {
    if(control->queues[i] == NULL) continue;
    if(control->export_scheduled && i == DT_JOB_QUEUE_USER_EXPORT) continue;
    _dt_job_t *_job = (_dt_job_t *)control->queues[i]->data;
    if(_job->priority > max_priority)
    {
      max_priority = _job->priority;
      job = _job;
      winner_queue = i;
    }
  }
 
  if(IS_NULL_PTR(job))
  {
    dt_pthread_mutex_unlock(&control->queue_mutex);
    return NULL;
  }
 
  // the order of the queues in control->queues matches our priority, and we only update job when the priority
  // is strictly bigger
  // invariant -> job is the one we are looking for
 
  // remove the to be scheduled job from its queue
  GList **queue = &control->queues[winner_queue];
  *queue = g_list_delete_link(*queue, *queue);
  control->queue_length[winner_queue]--;
  if(winner_queue == DT_JOB_QUEUE_USER_EXPORT) control->export_scheduled = TRUE;
 
  // and place it in scheduled job array (for job deduping)
  control->job[dt_control_get_threadid()] = job;
 
  // increment the priorities of the others
  for(int i = 0; i < DT_JOB_QUEUE_MAX; i++)
  {
    if(i == winner_queue || control->queues[i] == NULL) continue;
    ((_dt_job_t *)control->queues[i]->data)->priority++;
  }
 
  dt_pthread_mutex_unlock(&control->queue_mutex);
 
  return job;
}
 
static void dt_control_job_execute(_dt_job_t *job)
{
  dt_print(DT_DEBUG_CONTROL, "[run_job+] %02d %f ", DT_CTL_WORKER_RESERVED + dt_control_get_threadid(),
           dt_get_wtime());
  dt_control_job_print(job);
  dt_print(DT_DEBUG_CONTROL, "\n");
 
  dt_control_job_set_state(job, DT_JOB_STATE_RUNNING);
 
  /* execute job */
  job->result = job->execute(job);
 
  dt_control_job_set_state(job, DT_JOB_STATE_FINISHED);
 
  dt_print(DT_DEBUG_CONTROL, "[run_job-] %02d %f ", DT_CTL_WORKER_RESERVED + dt_control_get_threadid(),
           dt_get_wtime());
  dt_control_job_print(job);
  dt_print(DT_DEBUG_CONTROL, "\n");
}
 
static int32_t dt_control_run_job(dt_control_t *control)
{
  _dt_job_t *job = dt_control_schedule_job(control);
 
  if(IS_NULL_PTR(job)) return -1;
 
  /* change state to running */
  dt_pthread_mutex_lock(&job->wait_mutex);
  if(dt_control_job_get_state(job) == DT_JOB_STATE_QUEUED)
    dt_control_job_execute(job);
 
  dt_pthread_mutex_unlock(&job->wait_mutex);
 
  // remove the job from scheduled job array (for job deduping)
  dt_pthread_mutex_lock(&control->queue_mutex);
  control->job[dt_control_get_threadid()] = NULL;
  if(job->queue == DT_JOB_QUEUE_USER_EXPORT) control->export_scheduled = FALSE;
  dt_pthread_mutex_unlock(&control->queue_mutex);
 
  // and free it
  dt_control_job_dispose(job);
 
  return 0;
}
 
int32_t dt_control_add_job_res(dt_control_t *control, _dt_job_t *job, int32_t res)
{
  if(((unsigned int)res) >= DT_CTL_WORKER_RESERVED || IS_NULL_PTR(job))
  {
    dt_control_job_dispose(job);
    return 1;
  }
 
  // TODO: pthread cancel and restart in tough cases?
  dt_pthread_mutex_lock(&control->res_mutex);
 
  // if there is a job in the queue we have to discard that first
  if(control->job_res[res])
  {
    dt_control_job_set_state(control->job_res[res], DT_JOB_STATE_DISCARDED);
    dt_control_job_dispose(control->job_res[res]);
  }
 
  dt_print(DT_DEBUG_CONTROL, "[add_job_res] %d | ", res);
  dt_control_job_print(job);
  dt_print(DT_DEBUG_CONTROL, "\n");
 
  dt_control_job_set_state(job, DT_JOB_STATE_QUEUED);
  control->job_res[res] = job;
  control->new_res[res] = 1;
 
  dt_pthread_mutex_unlock(&control->res_mutex);
 
  dt_pthread_mutex_lock(&control->cond_mutex);
  pthread_cond_broadcast(&control->cond);
  dt_pthread_mutex_unlock(&control->cond_mutex);
 
  return 0;
}
 
void dt_control_flush_jobs_queue(dt_control_t *control, dt_job_queue_t queue_id)
{
  dt_pthread_mutex_lock(&control->queue_mutex);
 
  int count = 0;
 
  for(int k = 0; k < control->num_threads; k++)
  {
    _dt_job_t *job = (_dt_job_t *)control->job[k];
    if(!IS_NULL_PTR(job))
    {
      dt_control_job_cancel(job);
      count++;
    }
  }
 
  dt_print(DT_DEBUG_CONTROL, "[jobs] flushed %i pending jobs from queue %i\n", count, queue_id);
 
  dt_pthread_mutex_unlock(&control->queue_mutex);
}
 
int dt_control_add_job(dt_control_t *control, dt_job_queue_t queue_id, _dt_job_t *job)
{
  if(((unsigned int)queue_id) >= DT_JOB_QUEUE_MAX || IS_NULL_PTR(job))
  {
    dt_control_job_dispose(job);
    return 1;
  }
 
  if(!control->running)
  {
    // whatever we are adding here won't be scheduled as the system isn't running. execute it synchronous instead.
    dt_pthread_mutex_lock(&job->wait_mutex); // is that even needed?
    dt_control_job_execute(job);
    dt_pthread_mutex_unlock(&job->wait_mutex);
 
    dt_control_job_dispose(job);
    return 0;
  }
 
  job->queue = queue_id;
 
  _dt_job_t *job_for_disposal = NULL;
 
  dt_pthread_mutex_lock(&control->queue_mutex);
 
  GList **queue = &control->queues[queue_id];
  size_t length = control->queue_length[queue_id];
 
  dt_print(DT_DEBUG_CONTROL, "[add_job] %" G_GSIZE_FORMAT " | ", length);
  dt_control_job_print(job);
  dt_print(DT_DEBUG_CONTROL, "\n");
 
  if(queue_id == DT_JOB_QUEUE_SYSTEM_FG)
  {
    // this is a stack with limited size and bubble up and all that stuff
    job->priority = DT_CONTROL_FG_PRIORITY;
 
    // check if we have already scheduled the job
    for(int k = 0; k < control->num_threads; k++)
    {
      _dt_job_t *other_job = (_dt_job_t *)control->job[k];
      if(dt_control_job_equal(job, other_job))
      {
        dt_print(DT_DEBUG_CONTROL, "[add_job] found job already in scheduled: ");
        dt_control_job_print(other_job);
        dt_print(DT_DEBUG_CONTROL, "\n");
 
        dt_pthread_mutex_unlock(&control->queue_mutex);
 
        dt_control_job_set_state(job, DT_JOB_STATE_DISCARDED);
        dt_control_job_dispose(job);
 
        return 0; // there can't be any further copy
      }
    }
 
    // if the job is already in the queue -> move it to the top
    for(GList *iter = *queue; iter; iter = g_list_next(iter))
    {
      _dt_job_t *other_job = (_dt_job_t *)iter->data;
      if(dt_control_job_equal(job, other_job))
      {
        dt_print(DT_DEBUG_CONTROL, "[add_job] found job already in queue: ");
        dt_control_job_print(other_job);
        dt_print(DT_DEBUG_CONTROL, "\n");
 
        *queue = g_list_delete_link(*queue, iter);
        length--;
 
        job_for_disposal = job;
 
        job = other_job;
        break; // there can't be any further copy in the list
      }
    }
 
    // now we can add the new job to the list
    *queue = g_list_prepend(*queue, job);
    length++;
 
    // and take care of the maximal queue size
    if(length > DT_CONTROL_MAX_JOBS)
    {
      GList *last = g_list_last(*queue);
      dt_control_job_set_state((_dt_job_t *)last->data, DT_JOB_STATE_DISCARDED);
      dt_control_job_dispose((_dt_job_t *)last->data);
      *queue = g_list_delete_link(*queue, last);
      length--;
    }
 
    control->queue_length[queue_id] = length;
  }
  else
  {
    // the rest are FIFOs
    if(queue_id == DT_JOB_QUEUE_USER_BG ||
       queue_id == DT_JOB_QUEUE_USER_EXPORT ||
       queue_id == DT_JOB_QUEUE_SYSTEM_BG)
      job->priority = 0;
    else
      job->priority = DT_CONTROL_FG_PRIORITY;
    *queue = g_list_append(*queue, job);
    control->queue_length[queue_id]++;
  }
  dt_control_job_set_state(job, DT_JOB_STATE_QUEUED);
  dt_pthread_mutex_unlock(&control->queue_mutex);
 
  // notify workers
  dt_pthread_mutex_lock(&control->cond_mutex);
  pthread_cond_broadcast(&control->cond);
  dt_pthread_mutex_unlock(&control->cond_mutex);
 
  // dispose of dropped job, if any
  dt_control_job_set_state(job_for_disposal, DT_JOB_STATE_DISCARDED);
  dt_control_job_dispose(job_for_disposal);
 
  return 0;
}
 
static __thread int threadid = -1;
 
int32_t dt_control_get_threadid()
{
  if(threadid > -1) return threadid;
  return dt_control_get_global()->num_threads;
}
 
static int32_t dt_control_get_threadid_res()
{
  if(threadid > -1) return threadid;
  return DT_CTL_WORKER_RESERVED;
}
 
static void *dt_control_work_res(void *ptr)
{
#ifdef _OPENMP // need to do this in every thread
  omp_set_num_threads(dt_get_num_openmp_threads());
#endif
  worker_thread_parameters_t *params = (worker_thread_parameters_t *)ptr;
  dt_control_t *s = params->self;
  threadid = params->threadid;
  char name[16] = {0};
  snprintf(name, sizeof(name), "worker res %d", threadid);
  dt_pthread_setname(name);
  dt_free(params);
  int32_t threadid_res = dt_control_get_threadid_res();
  while(dt_control_running())
  {
    // dt_print(DT_DEBUG_CONTROL, "[control_work] %d\n", threadid_res);
    if(dt_control_run_job_res(s, threadid_res) < 0)
    {
      // wait for a new job.
      int old;
      pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &old);
      dt_pthread_mutex_lock(&s->cond_mutex);
      dt_pthread_cond_wait(&s->cond, &s->cond_mutex);
      dt_pthread_mutex_unlock(&s->cond_mutex);
      int tmp;
      pthread_setcancelstate(old, &tmp);
    }
  }
  return NULL;
}
 
static void *dt_control_worker_kicker(void *ptr)
{
  dt_control_t *control = (dt_control_t *)ptr;
  dt_pthread_setname("kicker");
  while(dt_control_running())
  {
    sleep(2);
    dt_pthread_mutex_lock(&control->cond_mutex);
    pthread_cond_broadcast(&control->cond);
    dt_pthread_mutex_unlock(&control->cond_mutex);
  }
  return NULL;
}
 
static void *dt_control_work(void *ptr)
{
#ifdef _OPENMP // need to do this in every thread
  omp_set_num_threads(dt_get_num_openmp_threads());
#endif
  worker_thread_parameters_t *params = (worker_thread_parameters_t *)ptr;
  dt_control_t *control = params->self;
  threadid = params->threadid;
  char name[16] = {0};
  snprintf(name, sizeof(name), "worker %d", threadid);
  dt_pthread_setname(name);
  dt_free(params);
  // int32_t threadid = dt_control_get_threadid();
  while(dt_control_running())
  {
    // dt_print(DT_DEBUG_CONTROL, "[control_work] %d\n", threadid);
    if(dt_control_run_job(control) < 0)
    {
      // wait for a new job.
      dt_pthread_mutex_lock(&control->cond_mutex);
      dt_pthread_cond_wait(&control->cond, &control->cond_mutex);
      dt_pthread_mutex_unlock(&control->cond_mutex);
    }
  }
  return NULL;
}
 
// convenience functions to have a progress bar for the job.
// this allows to show the gui indicator of the job even before it got scheduled
void dt_control_job_add_progress(dt_job_t *job, const char *message, gboolean cancellable)
{
  if(IS_NULL_PTR(job)) return;
  job->progress = dt_control_progress_create(dt_control_get_global(), TRUE, message);
  if(cancellable)
    dt_control_progress_attach_job(dt_control_get_global(), job->progress, job);
}
 
void dt_control_job_set_progress_message(dt_job_t *job, const char *message)
{
  if(IS_NULL_PTR(job) || !job->progress) return;
  dt_control_progress_set_message(dt_control_get_global(), job->progress, message);
}
 
void dt_control_job_set_progress(dt_job_t *job, double value)
{
  if(IS_NULL_PTR(job) || !job->progress) return;
  dt_control_progress_set_progress(dt_control_get_global(), job->progress, value);
}
 
double dt_control_job_get_progress(dt_job_t *job)
{
  if(IS_NULL_PTR(job) || !job->progress) return -1.0;
  return dt_control_progress_get_progress(job->progress);
}
 
 
// moved out of control.c to be able to make some helper functions static
void dt_control_jobs_init(dt_control_t *control)
{
  // start threads
  control->num_threads = dt_worker_threads();
  control->thread = (pthread_t *)calloc(control->num_threads, sizeof(pthread_t));
  control->job = (dt_job_t **)calloc(control->num_threads, sizeof(dt_job_t *));
  dt_pthread_mutex_lock(&control->run_mutex);
  control->running = 1;
  dt_pthread_mutex_unlock(&control->run_mutex);
  for(int k = 0; k < control->num_threads; k++)
  {
    worker_thread_parameters_t *params
        = (worker_thread_parameters_t *)calloc(1, sizeof(worker_thread_parameters_t));
    params->self = control;
    params->threadid = k;
    dt_pthread_create(&control->thread[k], dt_control_work, params, FALSE);
  }
 
  /* create queue kicker thread */
  dt_pthread_create(&control->kick_on_workers_thread, dt_control_worker_kicker, control, FALSE);
 
  for(int k = 0; k < DT_CTL_WORKER_RESERVED; k++)
  {
    control->job_res[k] = NULL;
    control->new_res[k] = 0;
    worker_thread_parameters_t *params
        = (worker_thread_parameters_t *)calloc(1, sizeof(worker_thread_parameters_t));
    params->self = control;
    params->threadid = k;
    dt_pthread_create(&control->thread_res[k], dt_control_work_res, params, TRUE);
  }
}
 
void dt_control_jobs_drain(dt_control_t *control)
{
  // Detach every queued job under the lock, then dispose them outside it. Disposing a job runs
  // its callbacks (state_changed_cb via DT_JOB_STATE_DISPOSED, then params_destroy), which for
  // module jobs point into a plug-in .so -- so these callbacks must NOT be invoked while holding
  // queue_mutex (re-entrancy), and the whole drain must happen before those .so files are
  // unloaded. Workers are already joined when this runs, so detaching the lists is race-free.
  GList *doomed = NULL;
  dt_pthread_mutex_lock(&control->queue_mutex);
  for(int i = 0; i < DT_JOB_QUEUE_MAX; i++)
  {
    doomed = g_list_concat(doomed, control->queues[i]);
    control->queues[i] = NULL;
    control->queue_length[i] = 0;
  }
  control->export_scheduled = FALSE;
  dt_pthread_mutex_unlock(&control->queue_mutex);
 
  for(GList *l = doomed; l; l = g_list_next(l))
    dt_control_job_dispose((_dt_job_t *)l->data);
  g_list_free(doomed);
}
 
void dt_control_jobs_cleanup(dt_control_t *control)
{
  // Normally the queues were already drained by dt_control_shutdown() (while plug-in .so files
  // were still mapped). Drain again as a safety net for any path that skips shutdown (e.g. the
  // headless export run); it is a no-op when the queues are already empty.
  dt_control_jobs_drain(control);
 
  dt_free(control->job);
  dt_free(control->thread);
}
 
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