[GraphBolt][io_uring] Remove redundant mechanism. (#7686)

graphbolt/src/cnumpy.h

@@ -161,10 +161,11 @@ class OnDiskNpyArray : public torch::CustomClassHolder {
         }
         // If this is the first thread exiting, release the master thread's
         // ticket as well by releasing 2 slots. Otherwise, release 1 slot.
-        const auto releasing = acquirer_->exiting_first_.test_and_set() ? 1 : 2;
+        const auto releasing =
+            acquirer_->exiting_first_.test_and_set(std::memory_order_relaxed)
+                ? 1
+                : 2;
         semaphore_.release(releasing);
-        acquirer_->num_acquisitions_.fetch_add(
-            -releasing, std::memory_order_relaxed);
       }
 
       ::io_uring& get() const { return io_uring_queue_[thread_id_]; }
@@ -179,17 +180,16 @@ class OnDiskNpyArray : public torch::CustomClassHolder {
     }
 
     ~QueueAndBufferAcquirer() {
-      // If any of the worker threads exit early without being able to release
-      // the semaphore, we make sure to release it for them in the main thread.
-      const auto releasing = num_acquisitions_.load(std::memory_order_relaxed);
+      // If none of the worker threads acquire the semaphore, we make sure to
+      // release the ticket taken in the constructor.
+      const auto releasing =
+          exiting_first_.test_and_set(std::memory_order_relaxed) ? 0 : 1;
       semaphore_.release(releasing);
-      TORCH_CHECK(releasing == 0, "An io_uring worker thread didn't not exit.");
     }
 
     std::pair<UniqueQueue, char*> get() {
       // We consume a slot from the semaphore to use a queue.
       semaphore_.acquire();
-      num_acquisitions_.fetch_add(1, std::memory_order_relaxed);
       const auto thread_id = [&] {
         std::lock_guard lock(available_queues_mtx_);
         TORCH_CHECK(!available_queues_.empty());
@@ -205,7 +205,6 @@ class OnDiskNpyArray : public torch::CustomClassHolder {
    private:
     const OnDiskNpyArray* array_;
     std::atomic_flag exiting_first_ = ATOMIC_FLAG_INIT;
-    std::atomic<int> num_acquisitions_ = 1;
   };
 
 #endif  // HAVE_LIBRARY_LIBURING