2 files changed, 52 insertions, 6 deletions

diff --git a/src/util/u_queue.c b/src/util/u_queue.c
index 5e0c1095569..cd0b95b6ead 100644
--- a/src/util/u_queue.c
+++ b/src/util/u_queue.c
@@ -34,7 +34,8 @@
 #include "u_process.h"
 
 static void
-util_queue_kill_threads(struct util_queue *queue, unsigned keep_num_threads);
+util_queue_kill_threads(struct util_queue *queue, unsigned keep_num_threads,
+                        bool finish_locked);
 
 /****************************************************************************
  * Wait for all queues to assert idle when exit() is called.
@@ -55,7 +56,7 @@ atexit_handler(void)
    mtx_lock(&exit_mutex);
    /* Wait for all queues to assert idle. */
    LIST_FOR_EACH_ENTRY(iter, &queue_list, head) {
-      util_queue_kill_threads(iter, 0);
+      util_queue_kill_threads(iter, 0, false);
    }
    mtx_unlock(&exit_mutex);
 }
@@ -340,6 +341,39 @@ util_queue_create_thread(struct util_queue *queue, unsigned index)
    return true;
 }
 
+void
+util_queue_adjust_num_threads(struct util_queue *queue, unsigned num_threads)
+{
+   num_threads = MIN2(num_threads, queue->max_threads);
+   num_threads = MAX2(num_threads, 1);
+
+   mtx_lock(&queue->finish_lock);
+   unsigned old_num_threads = queue->num_threads;
+
+   if (num_threads == old_num_threads) {
+      mtx_unlock(&queue->finish_lock);
+      return;
+   }
+
+   if (num_threads < old_num_threads) {
+      util_queue_kill_threads(queue, num_threads, true);
+      mtx_unlock(&queue->finish_lock);
+      return;
+   }
+
+   /* Create threads.
+    *
+    * We need to update num_threads first, because threads terminate
+    * when thread_index < num_threads.
+    */
+   queue->num_threads = num_threads;
+   for (unsigned i = old_num_threads; i < num_threads; i++) {
+      if (!util_queue_create_thread(queue, i))
+         break;
+   }
+   mtx_unlock(&queue->finish_lock);
+}
+
 bool
 util_queue_init(struct util_queue *queue,
                 const char *name,
@@ -378,6 +412,7 @@ util_queue_init(struct util_queue *queue,
    }
 
    queue->flags = flags;
+   queue->max_threads = num_threads;
    queue->num_threads = num_threads;
    queue->max_jobs = max_jobs;
 
@@ -429,12 +464,14 @@ fail:
 }
 
 static void
-util_queue_kill_threads(struct util_queue *queue, unsigned keep_num_threads)
+util_queue_kill_threads(struct util_queue *queue, unsigned keep_num_threads,
+                        bool finish_locked)
 {
    unsigned i;
 
    /* Signal all threads to terminate. */
-   mtx_lock(&queue->finish_lock);
+   if (!finish_locked)
+      mtx_lock(&queue->finish_lock);
 
    if (keep_num_threads >= queue->num_threads) {
       mtx_unlock(&queue->finish_lock);
@@ -453,13 +490,14 @@ util_queue_kill_threads(struct util_queue *queue, unsigned keep_num_threads)
    for (i = keep_num_threads; i < old_num_threads; i++)
       thrd_join(queue->threads[i], NULL);
 
-   mtx_unlock(&queue->finish_lock);
+   if (!finish_locked)
+      mtx_unlock(&queue->finish_lock);
 }
 
 void
 util_queue_destroy(struct util_queue *queue)
 {
-   util_queue_kill_threads(queue, 0);
+   util_queue_kill_threads(queue, 0, false);
    remove_from_atexit_list(queue);
 
    cnd_destroy(&queue->has_space_cond);
diff --git a/src/util/u_queue.h b/src/util/u_queue.h
index 756fa53e1bf..2d269099c20 100644
--- a/src/util/u_queue.h
+++ b/src/util/u_queue.h
@@ -208,6 +208,7 @@ struct util_queue {
    thrd_t *threads;
    unsigned flags;
    int num_queued;
+   unsigned max_threads;
    unsigned num_threads; /* decreasing this number will terminate threads */
    int max_jobs;
    int write_idx, read_idx; /* ring buffer pointers */
@@ -235,6 +236,13 @@ void util_queue_drop_job(struct util_queue *queue,
 
 void util_queue_finish(struct util_queue *queue);
 
+/* Adjust the number of active threads. The new number of threads can't be
+ * greater than the initial number of threads at the creation of the queue,
+ * and it can't be less than 1.
+ */
+void
+util_queue_adjust_num_threads(struct util_queue *queue, unsigned num_threads);
+
 int64_t util_queue_get_thread_time_nano(struct util_queue *queue,
                                         unsigned thread_index);