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Android: per-runtime statics are read and written from runtime threads without a lock #99
Description
Summary
Several process-wide statics hold one entry per runtime, or one value set by every runtime. Each runtime reads and writes them from its own thread, with no lock. When workers start or stop while other runtimes are running, these are data races of the same kind as #93: a hash table can rehash under a concurrent reader, and a std::string can be reallocated under a concurrent reader.
| Static | Where | Written | Read |
|---|---|---|---|
JSR::env_to_jsr_cache (std::unordered_map) |
NativeScript/napi/v8/jsr.cpp |
js_create_napi_env, js_free_napi_env |
js_lock_env / js_unlock_env |
MetadataNode::s_arrayObjects (robin_hood::unordered_map) |
NativeScript/ffi/jni/{napi,jsi}/metadata/MetadataNode.cpp |
first array-constructor lookup in each runtime; erased on dispose | every array-constructor lookup |
envToPersistentSmartJSONStringify / rtToPersistentSmartJSONStringify (robin_hood::unordered_map) |
NativeScript/ffi/jni/{napi,jsi}/global/GlobalHelpers.cpp |
first JsonStringifyObject in each runtime; erased on dispose |
every JsonStringifyObject |
Constants::APP_ROOT_FOLDER_PATH (std::string) |
NativeScript/ffi/jni/{napi,jsi}/constants/Constants.cpp |
assigned in Runtime::Init of every runtime (NativeScript/runtime/android/{napi,jsi}/Runtime.cpp) |
module resolution, stack traces, MetadataNode origins, inspector |
The quickjs and primjs backends keep env_to_jsr_cache in a tns::SimpleMap, which has no lock either. The hermes backend already guards its copy with env_to_jsr_mutex.
MetadataNode::s_metadata_node_cache and (with #96) ArgConverter's long-conversion cache already use tns::ConcurrentMap, which is the pattern to follow for the maps.
Expected
Creating or disposing one runtime can't corrupt state another runtime is reading. Possible fixes:
- the per-runtime maps move to
tns::ConcurrentMapwith theGet/Insert/Removepattern used in fix(android): synchronize ArgConverter's per-runtime long cache #96, or become per-runtime state; APP_ROOT_FOLDER_PATHis set once per process, since every runtime computes the same value (filesRoot + "/app/"), or is guarded.
Environment
- Branch:
android-react-nativeat 64c7fed - Found by reading the code while fixing Android: data race on ArgConverter's process-wide long-conversion cache when workers start or stop concurrently #93; these were not seen crashing on their own.
Related: #93, #96, and #97 and #98 (the console timer maps).
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