1 files changed, 33 insertions, 14 deletions

diff --git a/compiler-rt/lib/xray/xray_buffer_queue.cc b/compiler-rt/lib/xray/xray_buffer_queue.cc
index 7ba755ac306..b049ab37516 100644
--- a/compiler-rt/lib/xray/xray_buffer_queue.cc
+++ b/compiler-rt/lib/xray/xray_buffer_queue.cc
@@ -16,6 +16,7 @@
 #include "sanitizer_common/sanitizer_common.h"
 #include "sanitizer_common/sanitizer_libc.h"
 
+#include <algorithm>
 #include <cstdlib>
 #include <tuple>
 
@@ -23,18 +24,21 @@ using namespace __xray;
 using namespace __sanitizer;
 
 BufferQueue::BufferQueue(std::size_t B, std::size_t N, bool &Success)
-    : BufferSize(B), Buffers(N), Mutex(), OwnedBuffers(), Finalizing{0} {
-  for (auto &T : Buffers) {
+    : BufferSize(B), Buffers(new std::tuple<Buffer, bool>[N]()),
+      BufferCount(N), Finalizing{0}, OwnedBuffers(new void *[N]()),
+      Next(Buffers.get()), First(Buffers.get()), LiveBuffers(0) {
+  for (size_t i = 0; i < N; ++i) {
+    auto &T = Buffers[i];
     void *Tmp = malloc(BufferSize);
     if (Tmp == nullptr) {
       Success = false;
       return;
     }
-
     auto &Buf = std::get<0>(T);
+    std::get<1>(T) = false;
     Buf.Buffer = Tmp;
     Buf.Size = B;
-    OwnedBuffers.emplace(Tmp);
+    OwnedBuffers[i] = Tmp;
   }
   Success = true;
 }
@@ -42,27 +46,41 @@ BufferQueue::BufferQueue(std::size_t B, std::size_t N, bool &Success)
 BufferQueue::ErrorCode BufferQueue::getBuffer(Buffer &Buf) {
   if (__sanitizer::atomic_load(&Finalizing, __sanitizer::memory_order_acquire))
     return ErrorCode::QueueFinalizing;
-  __sanitizer::BlockingMutexLock Guard(&Mutex);
-  if (Buffers.empty())
+  __sanitizer::SpinMutexLock Guard(&Mutex);
+  if (LiveBuffers == BufferCount)
     return ErrorCode::NotEnoughMemory;
-  auto &T = Buffers.front();
+
+  auto &T = *Next;
   auto &B = std::get<0>(T);
   Buf = B;
-  B.Buffer = nullptr;
-  B.Size = 0;
-  Buffers.pop_front();
+  ++LiveBuffers;
+
+  First = Next;
+  if (++Next == (Buffers.get() + BufferCount))
+    Next = Buffers.get();
+
   return ErrorCode::Ok;
 }
 
 BufferQueue::ErrorCode BufferQueue::releaseBuffer(Buffer &Buf) {
-  if (OwnedBuffers.count(Buf.Buffer) == 0)
+  // Blitz through the buffers array to find the buffer.
+  if (std::none_of(OwnedBuffers.get(), OwnedBuffers.get() + BufferCount,
+                   [&Buf](void *P) { return P == Buf.Buffer; }))
     return ErrorCode::UnrecognizedBuffer;
-  __sanitizer::BlockingMutexLock Guard(&Mutex);
+  __sanitizer::SpinMutexLock Guard(&Mutex);
+
+  // This points to a semantic bug, we really ought to not be releasing more
+  // buffers than we actually get.
+  if (LiveBuffers == 0)
+    return ErrorCode::NotEnoughMemory;
 
   // Now that the buffer has been released, we mark it as "used".
-  Buffers.emplace(Buffers.end(), Buf, true /* used */);
+  *First = std::make_tuple(Buf, true);
   Buf.Buffer = nullptr;
   Buf.Size = 0;
+  --LiveBuffers;
+  if (++First == (Buffers.get() + BufferCount))
+    First = Buffers.get();
   return ErrorCode::Ok;
 }
 
@@ -74,7 +92,8 @@ BufferQueue::ErrorCode BufferQueue::finalize() {
 }
 
 BufferQueue::~BufferQueue() {
-  for (auto &T : Buffers) {
+  for (auto I = Buffers.get(), E = Buffers.get() + BufferCount; I != E; ++I) {
+    auto &T = *I;
     auto &Buf = std::get<0>(T);
     free(Buf.Buffer);
   }