2 * Copyright 2017 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
21 #include <folly/portability/PThread.h>
22 #include <folly/portability/SysSyscall.h>
23 #include <folly/portability/Windows.h>
28 * Get a process-specific identifier for the current thread.
30 * The return value will uniquely identify the thread within the current
33 * Note that the return value does not necessarily correspond to an operating
34 * system thread ID. The return value is also only unique within the current
35 * process: getCurrentThreadID() may return the same value for two concurrently
36 * running threads in separate processes.
38 * The thread ID may be reused once the thread it corresponds to has been
41 inline uint64_t getCurrentThreadID() {
43 return uint64_t(pthread_mach_thread_np(pthread_self()));
45 return uint64_t(GetCurrentThreadId());
47 return uint64_t(pthread_self());
52 * Get the operating-system level thread ID for the current thread.
54 * The returned value will uniquely identify this thread on the system.
56 * This makes it more suitable for logging or displaying in user interfaces
57 * than the result of getCurrentThreadID().
59 * There are some potential caveats about this API, however:
61 * - In theory there is no guarantee that application threads map one-to-one to
62 * kernel threads. An application threading implementation could potentially
63 * share one OS thread across multiple application threads, and/or it could
64 * potentially move application threads between different OS threads over
65 * time. However, in practice all of the platforms we currently support have
66 * a one-to-one mapping between userspace threads and operating system
69 * - This API may also be slightly slower than getCurrentThreadID() on some
70 * platforms. This API may require a system call, where getCurrentThreadID()
71 * may only need to read thread-local memory.
73 * On Linux the returned value is a pid_t, and can be used in contexts
74 * requiring a thread pid_t.
76 * The thread ID may be reused once the thread it corresponds to has been
79 inline uint64_t getOSThreadID() {
82 pthread_threadid_np(nullptr, &tid);
85 return uint64_t(GetCurrentThreadId());
87 return uint64_t(syscall(FOLLY_SYS_gettid));