1 // Copyright 2012 The Chromium Authors
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "base/threading/platform_thread_win.h"
6
7 #include <stddef.h>
8
9 #include <string>
10
11 #include "base/allocator/partition_allocator/src/partition_alloc/partition_alloc_buildflags.h"
12 #include "base/debug/alias.h"
13 #include "base/debug/crash_logging.h"
14 #include "base/debug/profiler.h"
15 #include "base/feature_list.h"
16 #include "base/logging.h"
17 #include "base/memory/raw_ptr.h"
18 #include "base/metrics/histogram_macros.h"
19 #include "base/process/memory.h"
20 #include "base/strings/string_number_conversions.h"
21 #include "base/strings/utf_string_conversions.h"
22 #include "base/threading/scoped_blocking_call.h"
23 #include "base/threading/scoped_thread_priority.h"
24 #include "base/threading/thread_id_name_manager.h"
25 #include "base/threading/thread_restrictions.h"
26 #include "base/threading/threading_features.h"
27 #include "base/time/time_override.h"
28 #include "base/win/scoped_handle.h"
29 #include "base/win/windows_version.h"
30 #include "build/build_config.h"
31
32 #include <windows.h>
33
34 #if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC) && BUILDFLAG(USE_STARSCAN)
35 #include "base/allocator/partition_allocator/src/partition_alloc/starscan/pcscan.h"
36 #include "base/allocator/partition_allocator/src/partition_alloc/starscan/stack/stack.h"
37 #endif
38
39 namespace base {
40
41 BASE_FEATURE(kUseThreadPriorityLowest,
42 "UseThreadPriorityLowest",
43 base::FEATURE_DISABLED_BY_DEFAULT);
44 BASE_FEATURE(kAboveNormalCompositingBrowserWin,
45 "AboveNormalCompositingBrowserWin",
46 base::FEATURE_ENABLED_BY_DEFAULT);
47
48 BASE_FEATURE(kBackgroundThreadNormalMemoryPriorityWin,
49 "BackgroundThreadNormalMemoryPriorityWin",
50 base::FEATURE_DISABLED_BY_DEFAULT);
51
52 namespace {
53
54 // Flag used to set thread priority to |THREAD_PRIORITY_LOWEST| for
55 // |kUseThreadPriorityLowest| Feature.
56 std::atomic<bool> g_use_thread_priority_lowest{false};
57 // Flag used to map Compositing ThreadType |THREAD_PRIORITY_ABOVE_NORMAL| on the
58 // UI thread for |kAboveNormalCompositingBrowserWin| Feature.
59 std::atomic<bool> g_above_normal_compositing_browser{true};
60 // Flag used to set thread memory priority to |MEMORY_PRIORITY_NORMAL| on
61 // background threads for |kThreadNormalMemoryPriorityWin| Feature.
62 std::atomic<bool> g_background_thread_normal_memory_priority_win{false};
63
64 // These values are sometimes returned by ::GetThreadPriority().
65 constexpr int kWinDisplayPriority1 = 5;
66 constexpr int kWinDisplayPriority2 = 6;
67
68 // The information on how to set the thread name comes from
69 // a MSDN article: http://msdn2.microsoft.com/en-us/library/xcb2z8hs.aspx
70 const DWORD kVCThreadNameException = 0x406D1388;
71
72 typedef struct tagTHREADNAME_INFO {
73 DWORD dwType; // Must be 0x1000.
74 LPCSTR szName; // Pointer to name (in user addr space).
75 DWORD dwThreadID; // Thread ID (-1=caller thread).
76 DWORD dwFlags; // Reserved for future use, must be zero.
77 } THREADNAME_INFO;
78
79 // The SetThreadDescription API was brought in version 1607 of Windows 10.
80 typedef HRESULT(WINAPI* SetThreadDescription)(HANDLE hThread,
81 PCWSTR lpThreadDescription);
82
83 // This function has try handling, so it is separated out of its caller.
SetNameInternal(PlatformThreadId thread_id,const char * name)84 void SetNameInternal(PlatformThreadId thread_id, const char* name) {
85 THREADNAME_INFO info;
86 info.dwType = 0x1000;
87 info.szName = name;
88 info.dwThreadID = thread_id;
89 info.dwFlags = 0;
90
91 __try {
92 RaiseException(kVCThreadNameException, 0, sizeof(info) / sizeof(ULONG_PTR),
93 reinterpret_cast<ULONG_PTR*>(&info));
94 } __except (EXCEPTION_EXECUTE_HANDLER) {
95 }
96 }
97
98 struct ThreadParams {
99 raw_ptr<PlatformThread::Delegate> delegate;
100 bool joinable;
101 ThreadType thread_type;
102 MessagePumpType message_pump_type;
103 };
104
ThreadFunc(void * params)105 DWORD __stdcall ThreadFunc(void* params) {
106 ThreadParams* thread_params = static_cast<ThreadParams*>(params);
107 PlatformThread::Delegate* delegate = thread_params->delegate;
108 if (!thread_params->joinable)
109 base::DisallowSingleton();
110
111 if (thread_params->thread_type != ThreadType::kDefault)
112 internal::SetCurrentThreadType(thread_params->thread_type,
113 thread_params->message_pump_type);
114
115 // Retrieve a copy of the thread handle to use as the key in the
116 // thread name mapping.
117 PlatformThreadHandle::Handle platform_handle;
118 BOOL did_dup = DuplicateHandle(GetCurrentProcess(),
119 GetCurrentThread(),
120 GetCurrentProcess(),
121 &platform_handle,
122 0,
123 FALSE,
124 DUPLICATE_SAME_ACCESS);
125
126 #if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC) && BUILDFLAG(USE_STARSCAN)
127 partition_alloc::internal::PCScan::NotifyThreadCreated(
128 partition_alloc::internal::GetStackPointer());
129 #endif
130
131 win::ScopedHandle scoped_platform_handle;
132
133 if (did_dup) {
134 scoped_platform_handle.Set(platform_handle);
135 ThreadIdNameManager::GetInstance()->RegisterThread(
136 scoped_platform_handle.get(), PlatformThread::CurrentId());
137 }
138
139 delete thread_params;
140 delegate->ThreadMain();
141
142 if (did_dup) {
143 ThreadIdNameManager::GetInstance()->RemoveName(scoped_platform_handle.get(),
144 PlatformThread::CurrentId());
145 }
146
147 #if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC) && BUILDFLAG(USE_STARSCAN)
148 partition_alloc::internal::PCScan::NotifyThreadDestroyed();
149 #endif
150
151 // Ensure thread priority is at least NORMAL before initiating thread
152 // destruction. Thread destruction on Windows holds the LdrLock while
153 // performing TLS destruction which causes hangs if performed at background
154 // priority (priority inversion) (see: http://crbug.com/1096203).
155 if (::GetThreadPriority(::GetCurrentThread()) < THREAD_PRIORITY_NORMAL)
156 PlatformThread::SetCurrentThreadType(ThreadType::kDefault);
157
158 return 0;
159 }
160
161 // CreateThreadInternal() matches PlatformThread::CreateWithType(), except
162 // that |out_thread_handle| may be nullptr, in which case a non-joinable thread
163 // is created.
CreateThreadInternal(size_t stack_size,PlatformThread::Delegate * delegate,PlatformThreadHandle * out_thread_handle,ThreadType thread_type,MessagePumpType message_pump_type)164 bool CreateThreadInternal(size_t stack_size,
165 PlatformThread::Delegate* delegate,
166 PlatformThreadHandle* out_thread_handle,
167 ThreadType thread_type,
168 MessagePumpType message_pump_type) {
169 unsigned int flags = 0;
170 if (stack_size > 0) {
171 flags = STACK_SIZE_PARAM_IS_A_RESERVATION;
172 #if defined(ARCH_CPU_32_BITS)
173 } else {
174 // The process stack size is increased to give spaces to |RendererMain| in
175 // |chrome/BUILD.gn|, but keep the default stack size of other threads to
176 // 1MB for the address space pressure.
177 flags = STACK_SIZE_PARAM_IS_A_RESERVATION;
178 static BOOL is_wow64 = -1;
179 if (is_wow64 == -1 && !IsWow64Process(GetCurrentProcess(), &is_wow64))
180 is_wow64 = FALSE;
181 // When is_wow64 is set that means we are running on 64-bit Windows and we
182 // get 4 GiB of address space. In that situation we can afford to use 1 MiB
183 // of address space for stacks. When running on 32-bit Windows we only get
184 // 2 GiB of address space so we need to conserve. Typically stack usage on
185 // these threads is only about 100 KiB.
186 if (is_wow64)
187 stack_size = 1024 * 1024;
188 else
189 stack_size = 512 * 1024;
190 #endif
191 }
192
193 ThreadParams* params = new ThreadParams;
194 params->delegate = delegate;
195 params->joinable = out_thread_handle != nullptr;
196 params->thread_type = thread_type;
197 params->message_pump_type = message_pump_type;
198
199 // Using CreateThread here vs _beginthreadex makes thread creation a bit
200 // faster and doesn't require the loader lock to be available. Our code will
201 // have to work running on CreateThread() threads anyway, since we run code on
202 // the Windows thread pool, etc. For some background on the difference:
203 // http://www.microsoft.com/msj/1099/win32/win321099.aspx
204 void* thread_handle =
205 ::CreateThread(nullptr, stack_size, ThreadFunc, params, flags, nullptr);
206
207 if (!thread_handle) {
208 DWORD last_error = ::GetLastError();
209
210 switch (last_error) {
211 case ERROR_NOT_ENOUGH_MEMORY:
212 case ERROR_OUTOFMEMORY:
213 case ERROR_COMMITMENT_LIMIT:
214 TerminateBecauseOutOfMemory(stack_size);
215 break;
216
217 default:
218 static auto* last_error_crash_key = debug::AllocateCrashKeyString(
219 "create_thread_last_error", debug::CrashKeySize::Size32);
220 debug::SetCrashKeyString(last_error_crash_key,
221 base::NumberToString(last_error));
222 break;
223 }
224
225 delete params;
226 return false;
227 }
228
229 if (out_thread_handle)
230 *out_thread_handle = PlatformThreadHandle(thread_handle);
231 else
232 CloseHandle(thread_handle);
233 return true;
234 }
235
236 } // namespace
237
238 namespace internal {
239
AssertMemoryPriority(HANDLE thread,int memory_priority)240 void AssertMemoryPriority(HANDLE thread, int memory_priority) {
241 #if DCHECK_IS_ON()
242 static const auto get_thread_information_fn =
243 reinterpret_cast<decltype(&::GetThreadInformation)>(::GetProcAddress(
244 ::GetModuleHandle(L"Kernel32.dll"), "GetThreadInformation"));
245
246 DCHECK(get_thread_information_fn);
247
248 MEMORY_PRIORITY_INFORMATION memory_priority_information = {};
249 DCHECK(get_thread_information_fn(thread, ::ThreadMemoryPriority,
250 &memory_priority_information,
251 sizeof(memory_priority_information)));
252
253 DCHECK_EQ(memory_priority,
254 static_cast<int>(memory_priority_information.MemoryPriority));
255 #endif
256 }
257
258 } // namespace internal
259
260 // static
CurrentId()261 PlatformThreadId PlatformThread::CurrentId() {
262 return ::GetCurrentThreadId();
263 }
264
265 // static
CurrentRef()266 PlatformThreadRef PlatformThread::CurrentRef() {
267 return PlatformThreadRef(::GetCurrentThreadId());
268 }
269
270 // static
CurrentHandle()271 PlatformThreadHandle PlatformThread::CurrentHandle() {
272 return PlatformThreadHandle(::GetCurrentThread());
273 }
274
275 // static
YieldCurrentThread()276 void PlatformThread::YieldCurrentThread() {
277 ::Sleep(0);
278 }
279
280 // static
Sleep(TimeDelta duration)281 void PlatformThread::Sleep(TimeDelta duration) {
282 // When measured with a high resolution clock, Sleep() sometimes returns much
283 // too early. We may need to call it repeatedly to get the desired duration.
284 // PlatformThread::Sleep doesn't support mock-time, so this always uses
285 // real-time.
286 const TimeTicks end = subtle::TimeTicksNowIgnoringOverride() + duration;
287 for (TimeTicks now = subtle::TimeTicksNowIgnoringOverride(); now < end;
288 now = subtle::TimeTicksNowIgnoringOverride()) {
289 ::Sleep(static_cast<DWORD>((end - now).InMillisecondsRoundedUp()));
290 }
291 }
292
293 // static
SetName(const std::string & name)294 void PlatformThread::SetName(const std::string& name) {
295 SetNameCommon(name);
296
297 // The SetThreadDescription API works even if no debugger is attached.
298 static auto set_thread_description_func =
299 reinterpret_cast<SetThreadDescription>(::GetProcAddress(
300 ::GetModuleHandle(L"Kernel32.dll"), "SetThreadDescription"));
301 if (set_thread_description_func) {
302 set_thread_description_func(::GetCurrentThread(),
303 base::UTF8ToWide(name).c_str());
304 }
305
306 // The debugger needs to be around to catch the name in the exception. If
307 // there isn't a debugger, we are just needlessly throwing an exception.
308 if (!::IsDebuggerPresent())
309 return;
310
311 SetNameInternal(CurrentId(), name.c_str());
312 }
313
314 // static
GetName()315 const char* PlatformThread::GetName() {
316 return ThreadIdNameManager::GetInstance()->GetName(CurrentId());
317 }
318
319 // static
CreateWithType(size_t stack_size,Delegate * delegate,PlatformThreadHandle * thread_handle,ThreadType thread_type,MessagePumpType pump_type_hint)320 bool PlatformThread::CreateWithType(size_t stack_size,
321 Delegate* delegate,
322 PlatformThreadHandle* thread_handle,
323 ThreadType thread_type,
324 MessagePumpType pump_type_hint) {
325 DCHECK(thread_handle);
326 return CreateThreadInternal(stack_size, delegate, thread_handle, thread_type,
327 pump_type_hint);
328 }
329
330 // static
CreateNonJoinable(size_t stack_size,Delegate * delegate)331 bool PlatformThread::CreateNonJoinable(size_t stack_size, Delegate* delegate) {
332 return CreateNonJoinableWithType(stack_size, delegate, ThreadType::kDefault);
333 }
334
335 // static
CreateNonJoinableWithType(size_t stack_size,Delegate * delegate,ThreadType thread_type,MessagePumpType pump_type_hint)336 bool PlatformThread::CreateNonJoinableWithType(size_t stack_size,
337 Delegate* delegate,
338 ThreadType thread_type,
339 MessagePumpType pump_type_hint) {
340 return CreateThreadInternal(stack_size, delegate, nullptr /* non-joinable */,
341 thread_type, pump_type_hint);
342 }
343
344 // static
Join(PlatformThreadHandle thread_handle)345 void PlatformThread::Join(PlatformThreadHandle thread_handle) {
346 DCHECK(thread_handle.platform_handle());
347
348 DWORD thread_id = 0;
349 thread_id = ::GetThreadId(thread_handle.platform_handle());
350 DWORD last_error = 0;
351 if (!thread_id)
352 last_error = ::GetLastError();
353
354 // Record information about the exiting thread in case joining hangs.
355 base::debug::Alias(&thread_id);
356 base::debug::Alias(&last_error);
357
358 base::internal::ScopedBlockingCallWithBaseSyncPrimitives scoped_blocking_call(
359 FROM_HERE, base::BlockingType::MAY_BLOCK);
360
361 // Wait for the thread to exit. It should already have terminated but make
362 // sure this assumption is valid.
363 CHECK_EQ(WAIT_OBJECT_0,
364 WaitForSingleObject(thread_handle.platform_handle(), INFINITE));
365 CloseHandle(thread_handle.platform_handle());
366 }
367
368 // static
Detach(PlatformThreadHandle thread_handle)369 void PlatformThread::Detach(PlatformThreadHandle thread_handle) {
370 CloseHandle(thread_handle.platform_handle());
371 }
372
373 // static
CanChangeThreadType(ThreadType from,ThreadType to)374 bool PlatformThread::CanChangeThreadType(ThreadType from, ThreadType to) {
375 return true;
376 }
377
378 namespace {
379
SetCurrentThreadPriority(ThreadType thread_type,MessagePumpType pump_type_hint)380 void SetCurrentThreadPriority(ThreadType thread_type,
381 MessagePumpType pump_type_hint) {
382 if (thread_type == ThreadType::kCompositing &&
383 pump_type_hint == MessagePumpType::UI &&
384 !g_above_normal_compositing_browser) {
385 // Ignore kCompositing thread type for UI thread as Windows has a
386 // priority boost mechanism. See
387 // https://docs.microsoft.com/en-us/windows/win32/procthread/priority-boosts
388 return;
389 }
390
391 PlatformThreadHandle::Handle thread_handle =
392 PlatformThread::CurrentHandle().platform_handle();
393
394 if (!g_use_thread_priority_lowest && thread_type != ThreadType::kBackground) {
395 // Exit background mode if the new priority is not BACKGROUND. This is a
396 // no-op if not in background mode.
397 ::SetThreadPriority(thread_handle, THREAD_MODE_BACKGROUND_END);
398 // We used to DCHECK that memory priority is MEMORY_PRIORITY_NORMAL here,
399 // but found that it is not always the case (e.g. in the installer).
400 // crbug.com/1340578#c2
401 }
402
403 int desired_priority = THREAD_PRIORITY_ERROR_RETURN;
404 switch (thread_type) {
405 case ThreadType::kBackground:
406 // Using THREAD_MODE_BACKGROUND_BEGIN instead of THREAD_PRIORITY_LOWEST
407 // improves input latency and navigation time. See
408 // https://docs.google.com/document/d/16XrOwuwTwKWdgPbcKKajTmNqtB4Am8TgS9GjbzBYLc0
409 //
410 // MSDN recommends THREAD_MODE_BACKGROUND_BEGIN for threads that perform
411 // background work, as it reduces disk and memory priority in addition to
412 // CPU priority.
413 desired_priority =
414 g_use_thread_priority_lowest.load(std::memory_order_relaxed)
415 ? THREAD_PRIORITY_LOWEST
416 : THREAD_MODE_BACKGROUND_BEGIN;
417 break;
418 case ThreadType::kUtility:
419 desired_priority = THREAD_PRIORITY_BELOW_NORMAL;
420 break;
421 case ThreadType::kResourceEfficient:
422 case ThreadType::kDefault:
423 desired_priority = THREAD_PRIORITY_NORMAL;
424 break;
425 case ThreadType::kCompositing:
426 case ThreadType::kDisplayCritical:
427 desired_priority = THREAD_PRIORITY_ABOVE_NORMAL;
428 break;
429 case ThreadType::kRealtimeAudio:
430 desired_priority = THREAD_PRIORITY_TIME_CRITICAL;
431 break;
432 }
433 DCHECK_NE(desired_priority, THREAD_PRIORITY_ERROR_RETURN);
434
435 [[maybe_unused]] const BOOL cpu_priority_success =
436 ::SetThreadPriority(thread_handle, desired_priority);
437 DPLOG_IF(ERROR, !cpu_priority_success)
438 << "Failed to set thread priority to " << desired_priority;
439
440 if (g_background_thread_normal_memory_priority_win &&
441 desired_priority == THREAD_MODE_BACKGROUND_BEGIN) {
442 // Override the memory priority.
443 MEMORY_PRIORITY_INFORMATION memory_priority{.MemoryPriority =
444 MEMORY_PRIORITY_NORMAL};
445 [[maybe_unused]] const BOOL memory_priority_success =
446 SetThreadInformation(thread_handle, ::ThreadMemoryPriority,
447 &memory_priority, sizeof(memory_priority));
448 DPLOG_IF(ERROR, !memory_priority_success)
449 << "Set thread memory priority failed.";
450 }
451
452 if (!g_use_thread_priority_lowest && thread_type == ThreadType::kBackground) {
453 // In a background process, THREAD_MODE_BACKGROUND_BEGIN lowers the memory
454 // and I/O priorities but not the CPU priority (kernel bug?). Use
455 // THREAD_PRIORITY_LOWEST to also lower the CPU priority.
456 // https://crbug.com/901483
457 if (PlatformThread::GetCurrentThreadPriorityForTest() !=
458 ThreadPriorityForTest::kBackground) {
459 ::SetThreadPriority(thread_handle, THREAD_PRIORITY_LOWEST);
460 // We used to DCHECK that memory priority is MEMORY_PRIORITY_VERY_LOW
461 // here, but found that it is not always the case (e.g. in the installer).
462 // crbug.com/1340578#c2
463 }
464 }
465 }
466
SetCurrentThreadQualityOfService(ThreadType thread_type)467 void SetCurrentThreadQualityOfService(ThreadType thread_type) {
468 // QoS and power throttling were introduced in Win10 1709.
469 bool desire_ecoqos = false;
470 switch (thread_type) {
471 case ThreadType::kBackground:
472 case ThreadType::kUtility:
473 case ThreadType::kResourceEfficient:
474 desire_ecoqos = true;
475 break;
476 case ThreadType::kDefault:
477 case ThreadType::kCompositing:
478 case ThreadType::kDisplayCritical:
479 case ThreadType::kRealtimeAudio:
480 desire_ecoqos = false;
481 break;
482 }
483
484 THREAD_POWER_THROTTLING_STATE thread_power_throttling_state{
485 .Version = THREAD_POWER_THROTTLING_CURRENT_VERSION,
486 .ControlMask =
487 desire_ecoqos ? THREAD_POWER_THROTTLING_EXECUTION_SPEED : 0ul,
488 .StateMask =
489 desire_ecoqos ? THREAD_POWER_THROTTLING_EXECUTION_SPEED : 0ul,
490 };
491 [[maybe_unused]] const BOOL success = ::SetThreadInformation(
492 ::GetCurrentThread(), ::ThreadPowerThrottling,
493 &thread_power_throttling_state, sizeof(thread_power_throttling_state));
494 // Failure is expected on versions of Windows prior to RS3.
495 DPLOG_IF(ERROR, !success && win::GetVersion() >= win::Version::WIN10_RS3)
496 << "Failed to set EcoQoS to " << std::boolalpha << desire_ecoqos;
497 }
498
499 } // namespace
500
501 namespace internal {
502
SetCurrentThreadTypeImpl(ThreadType thread_type,MessagePumpType pump_type_hint)503 void SetCurrentThreadTypeImpl(ThreadType thread_type,
504 MessagePumpType pump_type_hint) {
505 SetCurrentThreadPriority(thread_type, pump_type_hint);
506 SetCurrentThreadQualityOfService(thread_type);
507 }
508
509 } // namespace internal
510
511 // static
GetCurrentThreadPriorityForTest()512 ThreadPriorityForTest PlatformThread::GetCurrentThreadPriorityForTest() {
513 static_assert(
514 THREAD_PRIORITY_IDLE < 0,
515 "THREAD_PRIORITY_IDLE is >= 0 and will incorrectly cause errors.");
516 static_assert(
517 THREAD_PRIORITY_LOWEST < 0,
518 "THREAD_PRIORITY_LOWEST is >= 0 and will incorrectly cause errors.");
519 static_assert(THREAD_PRIORITY_BELOW_NORMAL < 0,
520 "THREAD_PRIORITY_BELOW_NORMAL is >= 0 and will incorrectly "
521 "cause errors.");
522 static_assert(
523 THREAD_PRIORITY_NORMAL == 0,
524 "The logic below assumes that THREAD_PRIORITY_NORMAL is zero. If it is "
525 "not, ThreadPriorityForTest::kBackground may be incorrectly detected.");
526 static_assert(THREAD_PRIORITY_ABOVE_NORMAL >= 0,
527 "THREAD_PRIORITY_ABOVE_NORMAL is < 0 and will incorrectly be "
528 "translated to ThreadPriorityForTest::kBackground.");
529 static_assert(THREAD_PRIORITY_HIGHEST >= 0,
530 "THREAD_PRIORITY_HIGHEST is < 0 and will incorrectly be "
531 "translated to ThreadPriorityForTest::kBackground.");
532 static_assert(THREAD_PRIORITY_TIME_CRITICAL >= 0,
533 "THREAD_PRIORITY_TIME_CRITICAL is < 0 and will incorrectly be "
534 "translated to ThreadPriorityForTest::kBackground.");
535 static_assert(THREAD_PRIORITY_ERROR_RETURN >= 0,
536 "THREAD_PRIORITY_ERROR_RETURN is < 0 and will incorrectly be "
537 "translated to ThreadPriorityForTest::kBackground.");
538
539 const int priority =
540 ::GetThreadPriority(PlatformThread::CurrentHandle().platform_handle());
541
542 // Negative values represent a background priority. We have observed -3, -4,
543 // -6 when THREAD_MODE_BACKGROUND_* is used. THREAD_PRIORITY_IDLE,
544 // THREAD_PRIORITY_LOWEST and THREAD_PRIORITY_BELOW_NORMAL are other possible
545 // negative values.
546 if (priority < THREAD_PRIORITY_BELOW_NORMAL)
547 return ThreadPriorityForTest::kBackground;
548
549 switch (priority) {
550 case THREAD_PRIORITY_BELOW_NORMAL:
551 return ThreadPriorityForTest::kUtility;
552 case THREAD_PRIORITY_NORMAL:
553 return ThreadPriorityForTest::kNormal;
554 case kWinDisplayPriority1:
555 [[fallthrough]];
556 case kWinDisplayPriority2:
557 return ThreadPriorityForTest::kDisplay;
558 case THREAD_PRIORITY_ABOVE_NORMAL:
559 case THREAD_PRIORITY_HIGHEST:
560 return ThreadPriorityForTest::kDisplay;
561 case THREAD_PRIORITY_TIME_CRITICAL:
562 return ThreadPriorityForTest::kRealtimeAudio;
563 case THREAD_PRIORITY_ERROR_RETURN:
564 DPCHECK(false) << "::GetThreadPriority error";
565 }
566
567 NOTREACHED() << "::GetThreadPriority returned " << priority << ".";
568 return ThreadPriorityForTest::kNormal;
569 }
570
InitializePlatformThreadFeatures()571 void InitializePlatformThreadFeatures() {
572 g_use_thread_priority_lowest.store(
573 FeatureList::IsEnabled(kUseThreadPriorityLowest),
574 std::memory_order_relaxed);
575 g_above_normal_compositing_browser.store(
576 FeatureList::IsEnabled(kAboveNormalCompositingBrowserWin),
577 std::memory_order_relaxed);
578 g_background_thread_normal_memory_priority_win.store(
579 FeatureList::IsEnabled(kBackgroundThreadNormalMemoryPriorityWin),
580 std::memory_order_relaxed);
581 }
582
583 // static
GetDefaultThreadStackSize()584 size_t PlatformThread::GetDefaultThreadStackSize() {
585 return 0;
586 }
587
588 } // namespace base
589