[llvm] [Offload] Guard olMemAlloc/Free with a mutex (PR #153786)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-offload

Author: Ross Brunton (RossBrunton)

<details>
<summary>Changes</summary>

Both these functions update an `AllocInfoMap` structure in the context,
however they did not use any locks, causing random failures in threaded
code. Now they use a mutex.


---
Full diff: https://github.com/llvm/llvm-project/pull/153786.diff


1 Files Affected:

- (modified) offload/liboffload/src/OffloadImpl.cpp (+19-11) 


``````````diff
diff --git a/offload/liboffload/src/OffloadImpl.cpp b/offload/liboffload/src/OffloadImpl.cpp
index 1c9dfc69d445a..16459108d2c4a 100644
--- a/offload/liboffload/src/OffloadImpl.cpp
+++ b/offload/liboffload/src/OffloadImpl.cpp
@@ -125,6 +125,7 @@ struct OffloadContext {
   bool TracingEnabled = false;
   bool ValidationEnabled = true;
   DenseMap<void *, AllocInfo> AllocInfoMap{};
+  std::mutex AllocInfoMapMutex{};
   SmallVector<ol_platform_impl_t, 4> Platforms{};
   size_t RefCount;
 
@@ -449,26 +450,33 @@ Error olMemAlloc_impl(ol_device_handle_t Device, ol_alloc_type_t Type,
     return Alloc.takeError();
 
   *AllocationOut = *Alloc;
-  OffloadContext::get().AllocInfoMap.insert_or_assign(*Alloc,
-                                                      AllocInfo{Device, Type});
+  {
+    std::lock_guard<std::mutex> Lock(OffloadContext::get().AllocInfoMapMutex);
+    OffloadContext::get().AllocInfoMap.insert_or_assign(
+        *Alloc, AllocInfo{Device, Type});
+  }
   return Error::success();
 }
 
 Error olMemFree_impl(void *Address) {
-  if (!OffloadContext::get().AllocInfoMap.contains(Address))
-    return createOffloadError(ErrorCode::INVALID_ARGUMENT,
-                              "address is not a known allocation");
-
-  auto AllocInfo = OffloadContext::get().AllocInfoMap.at(Address);
-  auto Device = AllocInfo.Device;
-  auto Type = AllocInfo.Type;
+  ol_device_handle_t Device;
+  ol_alloc_type_t Type;
+  {
+    std::lock_guard<std::mutex> Lock(OffloadContext::get().AllocInfoMapMutex);
+    if (!OffloadContext::get().AllocInfoMap.contains(Address))
+      return createOffloadError(ErrorCode::INVALID_ARGUMENT,
+                                "address is not a known allocation");
+
+    auto AllocInfo = OffloadContext::get().AllocInfoMap.at(Address);
+    Device = AllocInfo.Device;
+    Type = AllocInfo.Type;
+    OffloadContext::get().AllocInfoMap.erase(Address);
+  }
 
   if (auto Res =
           Device->Device->dataDelete(Address, convertOlToPluginAllocTy(Type)))
     return Res;
 
-  OffloadContext::get().AllocInfoMap.erase(Address);
-
   return Error::success();
 }
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/153786