From ddd576ab87a16eb7fb06531da8040ac2ece0c9a3 Mon Sep 17 00:00:00 2001
From: Walter Erquinigo <wallace@fb.com>
Date: Wed, 3 Aug 2022 09:57:57 -0700
Subject: [PATCH] [lldb] Prevent race condition when fetching /proc/cpuinfo

@clayborg found a potential race condition when setting a static
variable. The fix seems simply to use call_once.

All relevant tests pass.

Differential Revision: https://reviews.llvm.org/D131081
---
 lldb/source/Plugins/Process/Linux/Procfs.cpp | 21 +++++++++-----------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/lldb/source/Plugins/Process/Linux/Procfs.cpp b/lldb/source/Plugins/Process/Linux/Procfs.cpp
index 7c0c55a4f208..f59883d1caff 100644
--- a/lldb/source/Plugins/Process/Linux/Procfs.cpp
+++ b/lldb/source/Plugins/Process/Linux/Procfs.cpp
@@ -7,9 +7,9 @@
 //===----------------------------------------------------------------------===//
 
 #include "Procfs.h"
-
 #include "lldb/Host/linux/Support.h"
 #include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Threading.h"
 
 using namespace lldb;
 using namespace lldb_private;
@@ -17,17 +17,14 @@ using namespace process_linux;
 using namespace llvm;
 
 Expected<ArrayRef<uint8_t>> lldb_private::process_linux::GetProcfsCpuInfo() {
-  static Optional<std::vector<uint8_t>> cpu_info;
-  if (!cpu_info) {
-    auto buffer_or_error = errorOrToExpected(getProcFile("cpuinfo"));
-    if (!buffer_or_error)
-      return buffer_or_error.takeError();
-    MemoryBuffer &buffer = **buffer_or_error;
-    cpu_info = std::vector<uint8_t>(
-        reinterpret_cast<const uint8_t *>(buffer.getBufferStart()),
-        reinterpret_cast<const uint8_t *>(buffer.getBufferEnd()));
-  }
-  return *cpu_info;
+  static ErrorOr<std::unique_ptr<MemoryBuffer>> cpu_info_or_err =
+      getProcFile("cpuinfo");
+
+  if (!*cpu_info_or_err)
+    cpu_info_or_err.getError();
+
+  MemoryBuffer &buffer = **cpu_info_or_err;
+  return arrayRefFromStringRef(buffer.getBuffer());
 }
 
 Expected<std::vector<cpu_id_t>>