1 files changed, 125 insertions, 4 deletions
diff --git a/lib/xray/tests/unit/buffer_queue_test.cc b/lib/xray/tests/unit/buffer_queue_test.cc
index c0d4ccb268d6..a30343e188f2 100644
--- a/lib/xray/tests/unit/buffer_queue_test.cc
+++ b/lib/xray/tests/unit/buffer_queue_test.cc
@@ -11,15 +11,21 @@
 //
 //===----------------------------------------------------------------------===//
 #include "xray_buffer_queue.h"
+#include "gmock/gmock.h"
 #include "gtest/gtest.h"
 
+#include <atomic>
 #include <future>
+#include <thread>
 #include <unistd.h>
 
 namespace __xray {
+namespace {
 
 static constexpr size_t kSize = 4096;
 
+using ::testing::Eq;
+
 TEST(BufferQueueTest, API) {
   bool Success = false;
   BufferQueue Buffers(kSize, 1, Success);
@@ -55,8 +61,13 @@ TEST(BufferQueueTest, ReleaseUnknown) {
   BufferQueue::Buffer Buf;
   Buf.Data = reinterpret_cast<void *>(0xdeadbeef);
   Buf.Size = kSize;
-  EXPECT_EQ(BufferQueue::ErrorCode::UnrecognizedBuffer,
-            Buffers.releaseBuffer(Buf));
+  Buf.Generation = Buffers.generation();
+
+  BufferQueue::Buffer Known;
+  EXPECT_THAT(Buffers.getBuffer(Known), Eq(BufferQueue::ErrorCode::Ok));
+  EXPECT_THAT(Buffers.releaseBuffer(Buf),
+              Eq(BufferQueue::ErrorCode::UnrecognizedBuffer));
+  EXPECT_THAT(Buffers.releaseBuffer(Known), Eq(BufferQueue::ErrorCode::Ok));
 }
 
 TEST(BufferQueueTest, ErrorsWhenFinalising) {
@@ -70,8 +81,7 @@ TEST(BufferQueueTest, ErrorsWhenFinalising) {
   BufferQueue::Buffer OtherBuf;
   ASSERT_EQ(BufferQueue::ErrorCode::QueueFinalizing,
             Buffers.getBuffer(OtherBuf));
-  ASSERT_EQ(BufferQueue::ErrorCode::QueueFinalizing,
-            Buffers.finalize());
+  ASSERT_EQ(BufferQueue::ErrorCode::QueueFinalizing, Buffers.finalize());
   ASSERT_EQ(Buffers.releaseBuffer(Buf), BufferQueue::ErrorCode::Ok);
 }
 
@@ -111,4 +121,115 @@ TEST(BufferQueueTest, Apply) {
   ASSERT_EQ(Count, 10);
 }
 
+TEST(BufferQueueTest, GenerationalSupport) {
+  bool Success = false;
+  BufferQueue Buffers(kSize, 10, Success);
+  ASSERT_TRUE(Success);
+  BufferQueue::Buffer B0;
+  ASSERT_EQ(Buffers.getBuffer(B0), BufferQueue::ErrorCode::Ok);
+  ASSERT_EQ(Buffers.finalize(),
+            BufferQueue::ErrorCode::Ok); // No more new buffers.
+
+  // Re-initialise the queue.
+  ASSERT_EQ(Buffers.init(kSize, 10), BufferQueue::ErrorCode::Ok);
+
+  BufferQueue::Buffer B1;
+  ASSERT_EQ(Buffers.getBuffer(B1), BufferQueue::ErrorCode::Ok);
+
+  // Validate that the buffers come from different generations.
+  ASSERT_NE(B0.Generation, B1.Generation);
+
+  // We stash the current generation, for use later.
+  auto PrevGen = B1.Generation;
+
+  // At this point, we want to ensure that we can return the buffer from the
+  // first "generation" would still be accepted in the new generation...
+  EXPECT_EQ(Buffers.releaseBuffer(B0), BufferQueue::ErrorCode::Ok);
+
+  // ... and that the new buffer is also accepted.
+  EXPECT_EQ(Buffers.releaseBuffer(B1), BufferQueue::ErrorCode::Ok);
+
+  // A next round will do the same, ensure that we are able to do multiple
+  // rounds in this case.
+  ASSERT_EQ(Buffers.finalize(), BufferQueue::ErrorCode::Ok);
+  ASSERT_EQ(Buffers.init(kSize, 10), BufferQueue::ErrorCode::Ok);
+  EXPECT_EQ(Buffers.getBuffer(B0), BufferQueue::ErrorCode::Ok);
+  EXPECT_EQ(Buffers.getBuffer(B1), BufferQueue::ErrorCode::Ok);
+
+  // Here we ensure that the generation is different from the previous
+  // generation.
+  EXPECT_NE(B0.Generation, PrevGen);
+  EXPECT_EQ(B1.Generation, B1.Generation);
+  ASSERT_EQ(Buffers.finalize(), BufferQueue::ErrorCode::Ok);
+  EXPECT_EQ(Buffers.releaseBuffer(B0), BufferQueue::ErrorCode::Ok);
+  EXPECT_EQ(Buffers.releaseBuffer(B1), BufferQueue::ErrorCode::Ok);
+}
+
+TEST(BufferQueueTest, GenerationalSupportAcrossThreads) {
+  bool Success = false;
+  BufferQueue Buffers(kSize, 10, Success);
+  ASSERT_TRUE(Success);
+
+  std::atomic<int> Counter{0};
+
+  // This function allows us to use thread-local storage to isolate the
+  // instances of the buffers to be used. It also allows us signal the threads
+  // of a new generation, and allow those to get new buffers. This is
+  // representative of how we expect the buffer queue to be used by the XRay
+  // runtime.
+  auto Process = [&] {
+    thread_local BufferQueue::Buffer B;
+    ASSERT_EQ(Buffers.getBuffer(B), BufferQueue::ErrorCode::Ok);
+    auto FirstGen = B.Generation;
+
+    // Signal that we've gotten a buffer in the thread.
+    Counter.fetch_add(1, std::memory_order_acq_rel);
+    while (!Buffers.finalizing()) {
+      Buffers.releaseBuffer(B);
+      Buffers.getBuffer(B);
+    }
+
+    // Signal that we've exited the get/release buffer loop.
+    Counter.fetch_sub(1, std::memory_order_acq_rel);
+    if (B.Data != nullptr)
+      Buffers.releaseBuffer(B);
+
+    // Spin until we find that the Buffer Queue is no longer finalizing.
+    while (Buffers.getBuffer(B) != BufferQueue::ErrorCode::Ok)
+      ;
+
+    // Signal that we've successfully gotten a buffer in the thread.
+    Counter.fetch_add(1, std::memory_order_acq_rel);
+
+    EXPECT_NE(FirstGen, B.Generation);
+    EXPECT_EQ(Buffers.releaseBuffer(B), BufferQueue::ErrorCode::Ok);
+
+    // Signal that we've successfully exited.
+    Counter.fetch_sub(1, std::memory_order_acq_rel);
+  };
+
+  // Spawn two threads running Process.
+  std::thread T0(Process), T1(Process);
+
+  // Spin until we find the counter is up to 2.
+  while (Counter.load(std::memory_order_acquire) != 2)
+    ;
+
+  // Then we finalize, then re-initialize immediately.
+  Buffers.finalize();
+
+  // Spin until we find the counter is down to 0.
+  while (Counter.load(std::memory_order_acquire) != 0)
+    ;
+
+  // Then we re-initialize.
+  EXPECT_EQ(Buffers.init(kSize, 10), BufferQueue::ErrorCode::Ok);
+
+  T0.join();
+  T1.join();
+
+  ASSERT_EQ(Counter.load(std::memory_order_acquire), 0);
+}
+
+} // namespace
 } // namespace __xray