LLVM  10.0.0svn
Threading.inc
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1 //===- Unix/Threading.inc - Unix Threading Implementation ----- -*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file provides the Unix specific implementation of Threading functions.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/ADT/SmallString.h"
14 #include "llvm/ADT/Twine.h"
15 
16 #if defined(__APPLE__)
17 #include <mach/mach_init.h>
18 #include <mach/mach_port.h>
19 #endif
20 
21 #include <pthread.h>
22 
23 #if defined(__FreeBSD__) || defined(__OpenBSD__)
24 #include <pthread_np.h> // For pthread_getthreadid_np() / pthread_set_name_np()
25 #endif
26 
27 #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
28 #include <errno.h>
29 #include <sys/sysctl.h>
30 #include <sys/user.h>
31 #include <unistd.h>
32 #endif
33 
34 #if defined(__NetBSD__)
35 #include <lwp.h> // For _lwp_self()
36 #endif
37 
38 #if defined(__linux__)
39 #include <sys/syscall.h> // For syscall codes
40 #include <unistd.h> // For syscall()
41 #endif
42 
43 namespace {
44  struct ThreadInfo {
45  void(*UserFn)(void *);
46  void *UserData;
47  };
48 }
49 
50 static void *ExecuteOnThread_Dispatch(void *Arg) {
51  ThreadInfo *TI = reinterpret_cast<ThreadInfo*>(Arg);
52  TI->UserFn(TI->UserData);
53  return nullptr;
54 }
55 
56 void llvm::llvm_execute_on_thread(void(*Fn)(void*), void *UserData,
57  unsigned RequestedStackSize) {
58  ThreadInfo Info = { Fn, UserData };
59  pthread_attr_t Attr;
60  pthread_t Thread;
61 
62  // Construct the attributes object.
63  if (::pthread_attr_init(&Attr) != 0)
64  return;
65 
66  // Set the requested stack size, if given.
67  if (RequestedStackSize != 0) {
68  if (::pthread_attr_setstacksize(&Attr, RequestedStackSize) != 0)
69  goto error;
70  }
71 
72  // Construct and execute the thread.
73  if (::pthread_create(&Thread, &Attr, ExecuteOnThread_Dispatch, &Info) != 0)
74  goto error;
75 
76  // Wait for the thread and clean up.
77  ::pthread_join(Thread, nullptr);
78 
79 error:
80  ::pthread_attr_destroy(&Attr);
81 }
82 
83 
84 uint64_t llvm::get_threadid() {
85 #if defined(__APPLE__)
86  // Calling "mach_thread_self()" bumps the reference count on the thread
87  // port, so we need to deallocate it. mach_task_self() doesn't bump the ref
88  // count.
89  thread_port_t Self = mach_thread_self();
90  mach_port_deallocate(mach_task_self(), Self);
91  return Self;
92 #elif defined(__FreeBSD__)
93  return uint64_t(pthread_getthreadid_np());
94 #elif defined(__NetBSD__)
95  return uint64_t(_lwp_self());
96 #elif defined(__ANDROID__)
97  return uint64_t(gettid());
98 #elif defined(__linux__)
99  return uint64_t(syscall(SYS_gettid));
100 #else
101  return uint64_t(pthread_self());
102 #endif
103 }
104 
105 
106 static constexpr uint32_t get_max_thread_name_length_impl() {
107 #if defined(__NetBSD__)
108  return PTHREAD_MAX_NAMELEN_NP;
109 #elif defined(__APPLE__)
110  return 64;
111 #elif defined(__linux__)
112 #if HAVE_PTHREAD_SETNAME_NP
113  return 16;
114 #else
115  return 0;
116 #endif
117 #elif defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
118  return 16;
119 #elif defined(__OpenBSD__)
120  return 32;
121 #else
122  return 0;
123 #endif
124 }
125 
127  return get_max_thread_name_length_impl();
128 }
129 
130 void llvm::set_thread_name(const Twine &Name) {
131  // Make sure the input is null terminated.
132  SmallString<64> Storage;
133  StringRef NameStr = Name.toNullTerminatedStringRef(Storage);
134 
135  // Truncate from the beginning, not the end, if the specified name is too
136  // long. For one, this ensures that the resulting string is still null
137  // terminated, but additionally the end of a long thread name will usually
138  // be more unique than the beginning, since a common pattern is for similar
139  // threads to share a common prefix.
140  // Note that the name length includes the null terminator.
141  if (get_max_thread_name_length() > 0)
142  NameStr = NameStr.take_back(get_max_thread_name_length() - 1);
143  (void)NameStr;
144 #if defined(__linux__)
145 #if (defined(__GLIBC__) && defined(_GNU_SOURCE)) || defined(__ANDROID__)
146 #if HAVE_PTHREAD_SETNAME_NP
147  ::pthread_setname_np(::pthread_self(), NameStr.data());
148 #endif
149 #endif
150 #elif defined(__FreeBSD__) || defined(__OpenBSD__)
151  ::pthread_set_name_np(::pthread_self(), NameStr.data());
152 #elif defined(__NetBSD__)
153  ::pthread_setname_np(::pthread_self(), "%s",
154  const_cast<char *>(NameStr.data()));
155 #elif defined(__APPLE__)
156  ::pthread_setname_np(NameStr.data());
157 #endif
158 }
159 
160 void llvm::get_thread_name(SmallVectorImpl<char> &Name) {
161  Name.clear();
162 
163 #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
164  int pid = ::getpid();
165  uint64_t tid = get_threadid();
166 
167  struct kinfo_proc *kp = nullptr, *nkp;
168  size_t len = 0;
169  int error;
170  int ctl[4] = { CTL_KERN, KERN_PROC, KERN_PROC_PID | KERN_PROC_INC_THREAD,
171  (int)pid };
172 
173  while (1) {
174  error = sysctl(ctl, 4, kp, &len, nullptr, 0);
175  if (kp == nullptr || (error != 0 && errno == ENOMEM)) {
176  // Add extra space in case threads are added before next call.
177  len += sizeof(*kp) + len / 10;
178  nkp = (struct kinfo_proc *)::realloc(kp, len);
179  if (nkp == nullptr) {
180  free(kp);
181  return;
182  }
183  kp = nkp;
184  continue;
185  }
186  if (error != 0)
187  len = 0;
188  break;
189  }
190 
191  for (size_t i = 0; i < len / sizeof(*kp); i++) {
192  if (kp[i].ki_tid == (lwpid_t)tid) {
193  Name.append(kp[i].ki_tdname, kp[i].ki_tdname + strlen(kp[i].ki_tdname));
194  break;
195  }
196  }
197  free(kp);
198  return;
199 #elif defined(__NetBSD__)
200  constexpr uint32_t len = get_max_thread_name_length_impl();
201  char buf[len];
202  ::pthread_getname_np(::pthread_self(), buf, len);
203 
204  Name.append(buf, buf + strlen(buf));
205 #elif defined(__OpenBSD__)
206  constexpr uint32_t len = get_max_thread_name_length_impl();
207  char buf[len];
208  ::pthread_get_name_np(::pthread_self(), buf, len);
209 
210  Name.append(buf, buf + strlen(buf));
211 #elif defined(__linux__)
212 #if HAVE_PTHREAD_GETNAME_NP
213  constexpr uint32_t len = get_max_thread_name_length_impl();
214  char Buffer[len] = {'\0'}; // FIXME: working around MSan false positive.
215  if (0 == ::pthread_getname_np(::pthread_self(), Buffer, len))
216  Name.append(Buffer, Buffer + strlen(Buffer));
217 #endif
218 #endif
219 }
220 
222 #if defined(__linux__) && defined(SCHED_IDLE)
223  // Some *really* old glibcs are missing SCHED_IDLE.
224  // http://man7.org/linux/man-pages/man3/pthread_setschedparam.3.html
225  // http://man7.org/linux/man-pages/man2/sched_setscheduler.2.html
226  sched_param priority;
227  // For each of the above policies, param->sched_priority must be 0.
228  priority.sched_priority = 0;
229  // SCHED_IDLE for running very low priority background jobs.
230  // SCHED_OTHER the standard round-robin time-sharing policy;
231  return !pthread_setschedparam(
232  pthread_self(),
233  Priority == ThreadPriority::Background ? SCHED_IDLE : SCHED_OTHER,
234  &priority)
235  ? SetThreadPriorityResult::SUCCESS
236  : SetThreadPriorityResult::FAILURE;
237 #elif defined(__APPLE__)
238  // https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/getpriority.2.html
239  // When setting a thread into background state the scheduling priority is set
240  // to lowest value, disk and network IO are throttled. Network IO will be
241  // throttled for any sockets the thread opens after going into background
242  // state. Any previously opened sockets are not affected.
243 
244  // https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man3/getiopolicy_np.3.html
245  // I/Os with THROTTLE policy are called THROTTLE I/Os. If a THROTTLE I/O
246  // request occurs within a small time window (usually a fraction of a second)
247  // of another NORMAL I/O request, the thread that issues the THROTTLE I/O is
248  // forced to sleep for a certain interval. This slows down the thread that
249  // issues the THROTTLE I/O so that NORMAL I/Os can utilize most of the disk
250  // I/O bandwidth.
251  return !setpriority(PRIO_DARWIN_THREAD, 0,
252  Priority == ThreadPriority::Background ? PRIO_DARWIN_BG
253  : 0)
254  ? SetThreadPriorityResult::SUCCESS
255  : SetThreadPriorityResult::FAILURE;
256 #endif
257  return SetThreadPriorityResult::FAILURE;
258 }
void set_thread_name(const Twine &Name)
Set the name of the current thread.
uint64_t Thread
Definition: Profile.cpp:48
amdgpu Simplify well known AMD library false FunctionCallee Value const Twine & Name
#define error(X)
uint32_t get_max_thread_name_length()
Get the maximum length of a thread name on this platform.
void get_thread_name(SmallVectorImpl< char > &Name)
Get the name of the current thread.
Analysis containing CSE Info
Definition: CSEInfo.cpp:20
SetThreadPriorityResult
If priority is Background tries to lower current threads priority such that it does not affect foregr...
Definition: Threading.h:181
amdgpu Simplify well known AMD library false FunctionCallee Value * Arg
uint64_t get_threadid()
Return the current thread id, as used in various OS system calls.
void llvm_execute_on_thread(void(*UserFn)(void *), void *UserData, unsigned RequestedStackSize=0)
llvm_execute_on_thread - Execute the given UserFn on a separate thread, passing it the provided UserD...
SetThreadPriorityResult set_thread_priority(ThreadPriority Priority)
ThreadPriority
Definition: Threading.h:171