| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #include "os/thread_local_storage.h" |
| |
| #include <jni.h> |
| #include <stdio.h> |
| #include <windows.h> |
| |
| /** Key that allows us to retrieve thread-local storage */ |
| static DWORD gTlsIndex = TLS_OUT_OF_INDEXES; |
| |
| /** |
| * If the current thread has a JNIEnv in thread-local storage, then detaches the |
| * current thread from the JVM. |
| */ |
| static void detachCurrentThreadFromJvm() |
| { |
| JNIEnv *env = NULL; |
| JavaVM *vm; |
| jint ret; |
| if (threadLocalStorageGet(&env) || !env) { |
| return; |
| } |
| ret = (*env)->GetJavaVM(env, &vm); |
| if (ret) { |
| fprintf(stderr, |
| "detachCurrentThreadFromJvm: GetJavaVM failed with error %d\n", |
| ret); |
| (*env)->ExceptionDescribe(env); |
| } else { |
| (*vm)->DetachCurrentThread(vm); |
| } |
| } |
| |
| /** |
| * Unlike pthreads, the Windows API does not seem to provide a convenient way to |
| * hook a callback onto thread shutdown. However, the Windows portable |
| * executable format does define a concept of thread-local storage callbacks. |
| * Here, we define a function and instruct the linker to set a pointer to that |
| * function in the segment for thread-local storage callbacks. See page 85 of |
| * Microsoft Portable Executable and Common Object File Format Specification: |
| * http://msdn.microsoft.com/en-us/gg463119.aspx |
| * This technique only works for implicit linking (OS loads DLL on demand), not |
| * for explicit linking (user code calls LoadLibrary directly). This effectively |
| * means that we have a known limitation: libhdfs may not work correctly if a |
| * Windows application attempts to use it via explicit linking. |
| * |
| * @param h module handle |
| * @param reason the reason for calling the callback |
| * @param pv reserved, unused |
| */ |
| static void NTAPI tlsCallback(PVOID h, DWORD reason, PVOID pv) |
| { |
| DWORD tlsIndex; |
| switch (reason) { |
| case DLL_THREAD_DETACH: |
| detachCurrentThreadFromJvm(); |
| break; |
| case DLL_PROCESS_DETACH: |
| detachCurrentThreadFromJvm(); |
| tlsIndex = gTlsIndex; |
| gTlsIndex = TLS_OUT_OF_INDEXES; |
| if (!TlsFree(tlsIndex)) { |
| fprintf(stderr, "tlsCallback: TlsFree failed with error %d\n", |
| GetLastError()); |
| } |
| break; |
| default: |
| break; |
| } |
| } |
| |
| /* |
| * A variable named _tls_used contains the TLS directory, which contains a list |
| * of pointers to callback functions. Normally, the linker won't retain this |
| * variable unless the executable has implicit thread-local variables, defined |
| * using the __declspec(thread) extended storage-class modifier. libhdfs |
| * doesn't use __declspec(thread), and we have no guarantee that the executable |
| * linked to libhdfs will use __declspec(thread). By forcing the linker to |
| * reference _tls_used, we guarantee that the binary retains the TLS directory. |
| * See Microsoft Visual Studio 10.0/VC/crt/src/tlssup.c . |
| */ |
| #ifdef _WIN64 |
| #pragma comment(linker, "/INCLUDE:_tls_used") |
| #else |
| #pragma comment(linker, "/INCLUDE:__tls_used") |
| #endif |
| |
| /* |
| * We must retain a pointer to the callback function. Force the linker to keep |
| * this symbol, even though it appears that nothing in our source code uses it. |
| */ |
| #ifdef _WIN64 |
| #pragma comment(linker, "/INCLUDE:pTlsCallback") |
| #else |
| #pragma comment(linker, "/INCLUDE:_pTlsCallback") |
| #endif |
| |
| /* |
| * Define constant pointer to our callback, and tell the linker to pin it into |
| * the TLS directory so that it receives thread callbacks. Use external linkage |
| * to protect against the linker discarding the seemingly unused symbol. |
| */ |
| #pragma const_seg(".CRT$XLB") |
| extern const PIMAGE_TLS_CALLBACK pTlsCallback; |
| const PIMAGE_TLS_CALLBACK pTlsCallback = tlsCallback; |
| #pragma const_seg() |
| |
| int threadLocalStorageGet(JNIEnv **env) |
| { |
| LPVOID tls; |
| DWORD ret; |
| if (TLS_OUT_OF_INDEXES == gTlsIndex) { |
| gTlsIndex = TlsAlloc(); |
| if (TLS_OUT_OF_INDEXES == gTlsIndex) { |
| fprintf(stderr, |
| "threadLocalStorageGet: TlsAlloc failed with error %d\n", |
| TLS_OUT_OF_INDEXES); |
| return TLS_OUT_OF_INDEXES; |
| } |
| } |
| tls = TlsGetValue(gTlsIndex); |
| if (tls) { |
| *env = tls; |
| return 0; |
| } else { |
| ret = GetLastError(); |
| if (ERROR_SUCCESS == ret) { |
| /* Thread-local storage contains NULL, because we haven't set it yet. */ |
| *env = NULL; |
| return 0; |
| } else { |
| /* |
| * The API call failed. According to documentation, TlsGetValue cannot |
| * fail as long as the index is a valid index from a successful TlsAlloc |
| * call. This error handling is purely defensive. |
| */ |
| fprintf(stderr, |
| "threadLocalStorageGet: TlsGetValue failed with error %d\n", ret); |
| return ret; |
| } |
| } |
| } |
| |
| int threadLocalStorageSet(JNIEnv *env) |
| { |
| DWORD ret = 0; |
| if (!TlsSetValue(gTlsIndex, (LPVOID)env)) { |
| ret = GetLastError(); |
| fprintf(stderr, |
| "threadLocalStorageSet: TlsSetValue failed with error %d\n", |
| ret); |
| detachCurrentThreadFromJvm(env); |
| } |
| return ret; |
| } |