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Fix thread safety of LLM token buffer in Android JNI #17608

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Fix thread safety of LLM token buffer in Android JNI #17608

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32 changes: 17 additions & 15 deletions extension/android/jni/jni_layer_llama.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -78,7 +78,6 @@ bool utf8_check_validity(const char* str, size_t length) {
return true; // All bytes were valid
}

std::string token_buffer;
} // namespace

namespace executorch_jni {
Expand All @@ -89,21 +88,11 @@ class ExecuTorchLlmCallbackJni
constexpr static const char* kJavaDescriptor =
"Lorg/pytorch/executorch/extension/llm/LlmCallback;";

void onResult(std::string result) const {
void onResult(const std::string& result) const {
static auto cls = ExecuTorchLlmCallbackJni::javaClassStatic();
static const auto method =
cls->getMethod<void(facebook::jni::local_ref<jstring>)>("onResult");

token_buffer += result;
if (!utf8_check_validity(token_buffer.c_str(), token_buffer.size())) {
ET_LOG(
Info, "Current token buffer is not valid UTF-8. Waiting for more.");
return;
}
result = token_buffer;
token_buffer = "";
facebook::jni::local_ref<jstring> s = facebook::jni::make_jstring(result);
method(self(), s);
method(self(), facebook::jni::make_jstring(result));
}

void onStats(const llm::Stats& result) const {
Expand Down Expand Up @@ -245,6 +234,19 @@ class ExecuTorchLlmJni : public facebook::jni::HybridClass<ExecuTorchLlmJni> {
jint num_bos,
jint num_eos) {
float effective_temperature = temperature >= 0 ? temperature : temperature_;
std::string token_buffer;
auto token_callback = [callback, &token_buffer](const std::string& token) {
token_buffer += token;
if (!utf8_check_validity(token_buffer.c_str(), token_buffer.size())) {
ET_LOG(
Info, "Current token buffer is not valid UTF-8. Waiting for more.");
return;
}
std::string result = token_buffer;
token_buffer.clear();
callback->onResult(result);
};

if (model_type_category_ == MODEL_TYPE_CATEGORY_MULTIMODAL) {
std::vector<llm::MultimodalInput> inputs = prefill_inputs_;
prefill_inputs_.clear();
Expand All @@ -261,7 +263,7 @@ class ExecuTorchLlmJni : public facebook::jni::HybridClass<ExecuTorchLlmJni> {
multi_modal_runner_->generate(
std::move(inputs),
config,
[callback](const std::string& result) { callback->onResult(result); },
token_callback,
[callback](const llm::Stats& result) { callback->onStats(result); });
} else if (model_type_category_ == MODEL_TYPE_CATEGORY_LLM) {
executorch::extension::llm::GenerationConfig config{
Expand All @@ -274,7 +276,7 @@ class ExecuTorchLlmJni : public facebook::jni::HybridClass<ExecuTorchLlmJni> {
runner_->generate(
prompt->toStdString(),
config,
[callback](std::string result) { callback->onResult(result); },
token_callback,
[callback](const llm::Stats& result) { callback->onStats(result); });
}
return 0;
Expand Down
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