From 2ceb320ea35a14ef8f6df460314f85a40a7581de Mon Sep 17 00:00:00 2001
From: Tianyu Jiang <tianyuj@google.com>
Date: Mon, 17 Dec 2018 12:58:34 -0800
Subject: Check atomics in shared memory are lock free

when they are created in bufferhub server side in BufferNode, and client
side in BufferHubBuffer.

Fix: 117849512
Test: BufferHub_test BufferHubServer_test

Change-Id: Ifc5b681a6a86fa02cb598b33bf68dfefc07a76f9
---
 services/bufferhub/BufferNode.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'services/bufferhub/BufferNode.cpp')

diff --git a/services/bufferhub/BufferNode.cpp b/services/bufferhub/BufferNode.cpp
index cc87e15917..da19a6fb1d 100644
--- a/services/bufferhub/BufferNode.cpp
+++ b/services/bufferhub/BufferNode.cpp
@@ -2,6 +2,7 @@
 
 #include <bufferhub/BufferHubService.h>
 #include <bufferhub/BufferNode.h>
+#include <log/log.h>
 #include <ui/GraphicBufferAllocator.h>
 
 namespace android {
@@ -18,6 +19,13 @@ void BufferNode::InitializeMetadata() {
     fence_state_ = new (&metadata_header->fence_state) std::atomic<uint32_t>(0);
     active_clients_bit_mask_ =
             new (&metadata_header->active_clients_bit_mask) std::atomic<uint32_t>(0);
+    // The C++ standard recommends (but does not require) that lock-free atomic operations are
+    // also address-free, that is, suitable for communication between processes using shared
+    // memory.
+    LOG_ALWAYS_FATAL_IF(!std::atomic_is_lock_free(buffer_state_) ||
+                                !std::atomic_is_lock_free(fence_state_) ||
+                                !std::atomic_is_lock_free(active_clients_bit_mask_),
+                        "Atomic variables in ashmen are not lock free.");
 }
 
 // Allocates a new BufferNode.
-- 
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