[XRay][compiler-rt] XRay Buffer Queue

Summary:
This implements a simple buffer queue to manage a pre-allocated queue of
fixed-sized buffers to hold XRay records. We need this to support
Flight Data Recorder (FDR) mode. We also implement this as a sub-library
first to allow for development before actually using it in an
implementation.

Some important properties of the buffer queue:

- Thread-safe enqueueing/dequeueing of fixed-size buffers.
- Pre-allocation of buffers at construction.

Reviewers: majnemer, rSerge, echristo

Subscribers: mehdi_amini, mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D26232

llvm-svn: 287910

1 files changed, 80 insertions, 0 deletions

diff --git a/compiler-rt/lib/xray/tests/unit/buffer_queue_test.cc b/compiler-rt/lib/xray/tests/unit/buffer_queue_test.cc
new file mode 100644
index 00000000000..fd7d5afbb3a
--- /dev/null
+++ b/compiler-rt/lib/xray/tests/unit/buffer_queue_test.cc
@@ -0,0 +1,80 @@
+//===-- buffer_queue_test.cc ----------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is a part of XRay, a function call tracing system.
+//
+//===----------------------------------------------------------------------===//
+#include "xray_buffer_queue.h"
+#include "gtest/gtest.h"
+
+#include <future>
+#include <unistd.h>
+
+namespace __xray {
+
+static constexpr size_t kSize = 4096;
+
+TEST(BufferQueueTest, API) { BufferQueue Buffers(kSize, 1); }
+
+TEST(BufferQueueTest, GetAndRelease) {
+  BufferQueue Buffers(kSize, 1);
+  BufferQueue::Buffer Buf;
+  ASSERT_FALSE(Buffers.getBuffer(Buf));
+  ASSERT_NE(nullptr, Buf.Buffer);
+  ASSERT_FALSE(Buffers.releaseBuffer(Buf));
+  ASSERT_EQ(nullptr, Buf.Buffer);
+}
+
+TEST(BufferQueueTest, GetUntilFailed) {
+  BufferQueue Buffers(kSize, 1);
+  BufferQueue::Buffer Buf0;
+  EXPECT_FALSE(Buffers.getBuffer(Buf0));
+  BufferQueue::Buffer Buf1;
+  EXPECT_EQ(std::errc::not_enough_memory, Buffers.getBuffer(Buf1));
+  EXPECT_FALSE(Buffers.releaseBuffer(Buf0));
+}
+
+TEST(BufferQueueTest, ReleaseUnknown) {
+  BufferQueue Buffers(kSize, 1);
+  BufferQueue::Buffer Buf;
+  Buf.Buffer = reinterpret_cast<void *>(0xdeadbeef);
+  Buf.Size = kSize;
+  EXPECT_EQ(std::errc::argument_out_of_domain, Buffers.releaseBuffer(Buf));
+}
+
+TEST(BufferQueueTest, ErrorsWhenFinalising) {
+  BufferQueue Buffers(kSize, 2);
+  BufferQueue::Buffer Buf;
+  ASSERT_FALSE(Buffers.getBuffer(Buf));
+  ASSERT_NE(nullptr, Buf.Buffer);
+  ASSERT_FALSE(Buffers.finalize());
+  BufferQueue::Buffer OtherBuf;
+  ASSERT_EQ(std::errc::state_not_recoverable, Buffers.getBuffer(OtherBuf));
+  ASSERT_EQ(std::errc::state_not_recoverable, Buffers.finalize());
+  ASSERT_FALSE(Buffers.releaseBuffer(Buf));
+}
+
+TEST(BufferQueueTest, MultiThreaded) {
+  BufferQueue Buffers(kSize, 100);
+  auto F = [&] {
+    BufferQueue::Buffer B;
+    while (!Buffers.getBuffer(B)) {
+      Buffers.releaseBuffer(B);
+    }
+  };
+  auto T0 = std::async(std::launch::async, F);
+  auto T1 = std::async(std::launch::async, F);
+  auto T2 = std::async(std::launch::async, [&] {
+    while (!Buffers.finalize())
+      ;
+  });
+  F();
+}
+
+} // namespace __xray