Remove thread sanitizer lock order reversal warning for attribute context.

2 files changed, 25 insertions, 15 deletions

diff --git a/searchcore/src/vespa/searchcore/proton/attribute/imported_attributes_context.cpp b/searchcore/src/vespa/searchcore/proton/attribute/imported_attributes_context.cpp
index 0069a61b818..7a86a4c5f31 100644
--- a/searchcore/src/vespa/searchcore/proton/attribute/imported_attributes_context.cpp
+++ b/searchcore/src/vespa/searchcore/proton/attribute/imported_attributes_context.cpp
@@ -9,22 +9,34 @@
 
 using search::attribute::IAttributeVector;
 using search::attribute::ImportedAttributeVector;
-using LockGuard = std::lock_guard<std::mutex>;
 
 namespace proton {
 
 const IAttributeVector *
 ImportedAttributesContext::getOrCacheAttribute(const vespalib::string &name, AttributeCache &attributes,
-                                               bool stableEnumGuard, const LockGuard &) const
+                                               bool stableEnumGuard) const
 {
+    std::unique_lock guard(_cacheMutex);
+    std::shared_future<std::unique_ptr<AttributeReadGuard>> future_read_guard;
     auto itr = attributes.find(name);
     if (itr != attributes.end()) {
-        return itr->second->attribute();
+        future_read_guard = itr->second;
+        guard.unlock();
+    } else {
+        std::promise<std::unique_ptr<AttributeReadGuard>> promise;
+        future_read_guard = promise.get_future().share();
+        attributes.emplace(name, future_read_guard);
+        guard.unlock();
+        ImportedAttributeVector::SP result = _repo.get(name);
+        if (result) {
+            promise.set_value(result->makeReadGuard(stableEnumGuard));
+        } else {
+            promise.set_value(std::unique_ptr<AttributeReadGuard>());
+        }
     }
-    ImportedAttributeVector::SP result = _repo.get(name);
-    if (result) {
-        auto insRes = attributes.emplace(name, result->makeReadGuard(stableEnumGuard));
-        return insRes.first->second->attribute();
+    auto& read_guard = future_read_guard.get();
+    if (read_guard) {
+        return read_guard->attribute();
     } else {
         return nullptr;
     }
@@ -43,15 +55,13 @@ ImportedAttributesContext::~ImportedAttributesContext() = default;
 const IAttributeVector *
 ImportedAttributesContext::getAttribute(const vespalib::string &name) const
 {
-    LockGuard guard(_cacheMutex);
-    return getOrCacheAttribute(name, _guardedAttributes, false, guard);
+    return getOrCacheAttribute(name, _guardedAttributes, false);
 }
 
 const IAttributeVector *
 ImportedAttributesContext::getAttributeStableEnum(const vespalib::string &name) const
 {
-    LockGuard guard(_cacheMutex);
-    return getOrCacheAttribute(name, _enumGuardedAttributes, true, guard);
+    return getOrCacheAttribute(name, _enumGuardedAttributes, true);
 }
 
 void
@@ -67,7 +77,7 @@ ImportedAttributesContext::getAttributeList(std::vector<const IAttributeVector *
 void
 ImportedAttributesContext::releaseEnumGuards()
 {
-    LockGuard guard(_cacheMutex);
+    std::lock_guard guard(_cacheMutex);
     _enumGuardedAttributes.clear();
 }
 
diff --git a/searchcore/src/vespa/searchcore/proton/attribute/imported_attributes_context.h b/searchcore/src/vespa/searchcore/proton/attribute/imported_attributes_context.h
index 4b7058fdb83..33d6cef98ff 100644
--- a/searchcore/src/vespa/searchcore/proton/attribute/imported_attributes_context.h
+++ b/searchcore/src/vespa/searchcore/proton/attribute/imported_attributes_context.h
@@ -4,6 +4,7 @@
 #include <vespa/searchcommon/attribute/iattributecontext.h>
 #include <vespa/vespalib/stllike/hash_fun.h>
 #include <vespa/vespalib/stllike/hash_map.h>
+#include <future>
 #include <mutex>
 #include <unordered_map>
 
@@ -31,8 +32,7 @@ private:
     using ImportedAttributeVector = search::attribute::ImportedAttributeVector;
     using IAttributeFunctor = search::attribute::IAttributeFunctor;
 
-    using AttributeCache = std::unordered_map<vespalib::string, std::unique_ptr<AttributeReadGuard>, vespalib::hash<vespalib::string>>;
-    using LockGuard = std::lock_guard<std::mutex>;
+    using AttributeCache = std::unordered_map<vespalib::string, std::shared_future<std::unique_ptr<AttributeReadGuard>>, vespalib::hash<vespalib::string>>;
 
     const ImportedAttributesRepo &_repo;
     mutable AttributeCache _guardedAttributes;
@@ -40,7 +40,7 @@ private:
     mutable std::mutex _cacheMutex;
 
     const IAttributeVector *getOrCacheAttribute(const vespalib::string &name, AttributeCache &attributes,
-                                                bool stableEnumGuard, const LockGuard &) const;
+                                                bool stableEnumGuard) const;
 
 public:
     ImportedAttributesContext(const ImportedAttributesRepo &repo);