1/*
2 * Copyright 2017-present Facebook, Inc.
3 *
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
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
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.
15 */
16
17#include <folly/system/ThreadName.h>
18
19#include <type_traits>
20
21#include <folly/Portability.h>
22#include <folly/Traits.h>
23#include <folly/portability/PThread.h>
24#include <folly/portability/Windows.h>
25
26namespace folly {
27
28// This looks a bit weird, but it's necessary to avoid
29// having an undefined compiler function called.
30#if defined(__GLIBC__) && !defined(__APPLE__) && !defined(__ANDROID__)
31#if __GLIBC_PREREQ(2, 12)
32// has pthread_setname_np(pthread_t, const char*) (2 params)
33#define FOLLY_HAS_PTHREAD_SETNAME_NP_THREAD_NAME 1
34#endif
35#endif
36
37#if defined(__APPLE__)
38#if defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && \
39 __MAC_OS_X_VERSION_MIN_REQUIRED >= 1060
40// macOS 10.6+ has pthread_setname_np(const char*) (1 param)
41#define FOLLY_HAS_PTHREAD_SETNAME_NP_NAME 1
42#elif defined(__IPHONE_OS_VERSION_MIN_REQUIRED) && \
43 __IPHONE_OS_VERSION_MIN_REQUIRED >= 30200
44// iOS 3.2+ has pthread_setname_np(const char*) (1 param)
45#define FOLLY_HAS_PTHREAD_SETNAME_NP_NAME 1
46#endif
47#endif // defined(__APPLE__)
48
49namespace {
50
51#if FOLLY_HAVE_PTHREAD && !_WIN32
52pthread_t stdTidToPthreadId(std::thread::id tid) {
53 static_assert(
54 std::is_same<pthread_t, std::thread::native_handle_type>::value,
55 "This assumes that the native handle type is pthread_t");
56 static_assert(
57 sizeof(std::thread::native_handle_type) == sizeof(std::thread::id),
58 "This assumes std::thread::id is a thin wrapper around "
59 "std::thread::native_handle_type, but that doesn't appear to be true.");
60 // In most implementations, std::thread::id is a thin wrapper around
61 // std::thread::native_handle_type, which means we can do unsafe things to
62 // extract it.
63 pthread_t id;
64 std::memcpy(&id, &tid, sizeof(id));
65 return id;
66}
67#endif
68
69} // namespace
70
71bool canSetCurrentThreadName() {
72#if FOLLY_HAS_PTHREAD_SETNAME_NP_THREAD_NAME || \
73 FOLLY_HAS_PTHREAD_SETNAME_NP_NAME || _WIN32
74 return true;
75#else
76 return false;
77#endif
78}
79
80bool canSetOtherThreadName() {
81#if FOLLY_HAS_PTHREAD_SETNAME_NP_THREAD_NAME || _WIN32
82 return true;
83#else
84 return false;
85#endif
86}
87
88static constexpr size_t kMaxThreadNameLength = 16;
89
90Optional<std::string> getThreadName(std::thread::id id) {
91#if FOLLY_HAS_PTHREAD_SETNAME_NP_THREAD_NAME || \
92 FOLLY_HAS_PTHREAD_SETNAME_NP_NAME
93 std::array<char, kMaxThreadNameLength> buf;
94 if (pthread_getname_np(stdTidToPthreadId(id), buf.data(), buf.size()) != 0) {
95 return Optional<std::string>();
96 }
97 return folly::make_optional(std::string(buf.data()));
98#else
99 // There's not actually a way to get the thread name on Windows because
100 // thread names are a concept managed by the debugger, not the runtime.
101 return Optional<std::string>();
102#endif
103}
104
105Optional<std::string> getCurrentThreadName() {
106 return getThreadName(std::this_thread::get_id());
107}
108
109bool setThreadName(std::thread::id tid, StringPiece name) {
110 auto trimmedName = name.subpiece(0, kMaxThreadNameLength - 1).str();
111#if _WIN32
112 static_assert(
113 sizeof(unsigned int) == sizeof(std::thread::id),
114 "This assumes std::thread::id is a thin wrapper around "
115 "the thread id as an unsigned int, but that doesn't appear to be true.");
116
117// http://msdn.microsoft.com/en-us/library/xcb2z8hs.aspx
118#pragma pack(push, 8)
119 struct THREADNAME_INFO {
120 DWORD dwType; // Must be 0x1000
121 LPCSTR szName; // Pointer to name (in user address space)
122 DWORD dwThreadID; // Thread ID (-1 for caller thread)
123 DWORD dwFlags; // Reserved for future use; must be zero
124 };
125 union TNIUnion {
126 THREADNAME_INFO tni;
127 ULONG_PTR upArray[4];
128 };
129#pragma pack(pop)
130
131 static constexpr DWORD kMSVCException = 0x406D1388;
132
133 // std::thread::id is a thin wrapper around an integral thread id,
134 // so just extract the ID.
135 unsigned int id;
136 std::memcpy(&id, &tid, sizeof(id));
137
138 TNIUnion tniUnion = {0x1000, trimmedName.data(), id, 0};
139 // This has to be in a separate stack frame from trimmedName, which requires
140 // C++ object destruction semantics.
141 return [&]() {
142 __try {
143 RaiseException(kMSVCException, 0, 4, tniUnion.upArray);
144 } __except (
145 GetExceptionCode() == kMSVCException ? EXCEPTION_CONTINUE_EXECUTION
146 : EXCEPTION_EXECUTE_HANDLER) {
147 // Swallow the exception when a debugger isn't attached.
148 }
149 return true;
150 }();
151#else
152 name = name.subpiece(0, kMaxThreadNameLength - 1);
153 char buf[kMaxThreadNameLength] = {};
154 std::memcpy(buf, name.data(), name.size());
155 auto id = stdTidToPthreadId(tid);
156#if FOLLY_HAS_PTHREAD_SETNAME_NP_THREAD_NAME
157 return 0 == pthread_setname_np(id, buf);
158#elif FOLLY_HAS_PTHREAD_SETNAME_NP_NAME
159 // Since macOS 10.6 and iOS 3.2 it is possible for a thread to set its own
160 // name, but not that of some other thread.
161 if (pthread_equal(pthread_self(), id)) {
162 return 0 == pthread_setname_np(buf);
163 }
164 return false;
165#else
166 (void)id;
167 return false;
168#endif
169#endif
170}
171
172bool setThreadName(pthread_t pid, StringPiece name) {
173#if _WIN32
174 static_assert(
175 sizeof(unsigned int) == sizeof(std::thread::id),
176 "This assumes std::thread::id is a thin wrapper around "
177 "the thread id as an unsigned int, but that doesn't appear to be true.");
178
179 // std::thread::id is a thin wrapper around an integral thread id,
180 // so just stick the ID in.
181 unsigned int tid = pthread_getw32threadid_np(pid);
182 std::thread::id id;
183 std::memcpy(&id, &tid, sizeof(id));
184 return setThreadName(id, name);
185#else
186 static_assert(
187 std::is_same<pthread_t, std::thread::native_handle_type>::value,
188 "This assumes that the native handle type is pthread_t");
189 static_assert(
190 sizeof(std::thread::native_handle_type) == sizeof(std::thread::id),
191 "This assumes std::thread::id is a thin wrapper around "
192 "std::thread::native_handle_type, but that doesn't appear to be true.");
193 // In most implementations, std::thread::id is a thin wrapper around
194 // std::thread::native_handle_type, which means we can do unsafe things to
195 // extract it.
196 std::thread::id id;
197 std::memcpy(static_cast<void*>(&id), &pid, sizeof(id));
198 return setThreadName(id, name);
199#endif
200}
201
202bool setThreadName(StringPiece name) {
203 return setThreadName(std::this_thread::get_id(), name);
204}
205} // namespace folly
206