UCS/ASYNC: Use heap to process expired timers in batch

src/ucs/async/async.c

@@ -332,12 +332,19 @@ ucs_status_t ucs_async_dispatch_handlers(int *handler_ids, size_t count,
 ucs_status_t ucs_async_dispatch_timerq(ucs_timer_queue_t *timerq,
  ucs_time_t current_time)
 {
- size_t max_timers, num_timers = 0;
+ size_t num_timers = 0;
+ ucs_status_t status;
+ size_t max_timers, size;
  int *expired_timers;
  ucs_timer_t *timer;
 
- max_timers = ucs_max(1, ucs_timerq_size(timerq));
- expired_timers = ucs_alloca(max_timers * sizeof(*expired_timers));
+ max_timers = ucs_max(1, ucs_timerq_size(timerq));
+ size = max_timers * sizeof(*expired_timers);
+
+ expired_timers = ucs_alloc_on_stack(size, "async_dispatch_timerq");
+ if (expired_timers == NULL) {
+ return UCS_ERR_NO_MEMORY;
+ }
 
  ucs_timerq_for_each_expired(timer, timerq, current_time, {
  expired_timers[num_timers++] = timer->id;
@@ -346,8 +353,10 @@ ucs_status_t ucs_async_dispatch_timerq(ucs_timer_queue_t *timerq,
  }
  })
 
- return ucs_async_dispatch_handlers(expired_timers, num_timers,
- UCS_ASYNC_EVENT_DUMMY);
+ status = ucs_async_dispatch_handlers(expired_timers, num_timers,
+ UCS_ASYNC_EVENT_DUMMY);
+ ucs_free_on_stack(expired_timers, size);
+ return status;
 }
 
 ucs_status_t ucs_async_context_init(ucs_async_context_t *async, ucs_async_mode_t mode)

src/ucs/sys/compiler.h

@@ -56,6 +56,26 @@
  } \
  }
 
+/**
+ * Use stack or heap allocation depending on size. Free function @ref
+ * ucs_free_on_stack must always be called.
+ */
+#define ucs_alloc_on_stack(_size, _name) \
+ ({ \
+ size_t _sz = (_size); \
+ (_sz <= UCS_ALLOCA_MAX_SIZE) ? alloca(_sz) : ucs_malloc(_sz, _name); \
+ })
+
+/**
+ * Release function to be paired with @ref ucs_alloc_on_stack.
+ */
+#define ucs_free_on_stack(_ptr, _size) \
+ ({ \
+ if ((_size) > UCS_ALLOCA_MAX_SIZE) { \
+ ucs_free(_ptr); \
+ } \
+ })
+
 /**
  * alloca which makes sure the size is small enough.
  */