util/u_queue: add an option to resize the queue when it's full

Consider the following situation:
  mtx_lock(mutex);
  do_something();
  util_queue_add_job(...);
  mtx_unlock(mutex);

If the queue is full, util_queue_add_job will wait for a free slot.
If the job which is currently being executed tries to lock the mutex,
it will be stuck forever, because util_queue_add_job is stuck.

The deadlock can be trivially resolved by increasing the queue size
(reallocating the queue) in util_queue_add_job if the queue is full.
Then util_queue_add_job becomes wait-free.

radeonsi will use it.

Reviewed-by: Nicolai Hähnle <[email protected]>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/util/u_queue.h b/src/util/u_queue.h
index edd6babb5c7..ff713ae54d6 100644
--- a/src/util/u_queue.h
+++ b/src/util/u_queue.h
@@ -43,6 +43,7 @@ extern "C" {
 #endif
 
 #define UTIL_QUEUE_INIT_USE_MINIMUM_PRIORITY      (1 << 0)
+#define UTIL_QUEUE_INIT_RESIZE_IF_FULL            (1 << 1)
 
 /* Job completion fence.
  * Put this into your job structure.
@@ -69,6 +70,7 @@ struct util_queue {
    cnd_t has_queued_cond;
    cnd_t has_space_cond;
    thrd_t *threads;
+   unsigned flags;
    int num_queued;
    unsigned num_threads;
    int kill_threads;