| // Copyright 2012 The Chromium Authors |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| // WARNING: You should *NOT* be using this class directly. PlatformThread is |
| // the low-level platform-specific abstraction to the OS's threading interface. |
| // You should instead be using a message-loop driven Thread, see thread.h. |
| |
| #ifndef BASE_THREADING_PLATFORM_THREAD_H_ |
| #define BASE_THREADING_PLATFORM_THREAD_H_ |
| |
| #include <stddef.h> |
| |
| #include <iosfwd> |
| #include <limits> |
| #include <optional> |
| #include <type_traits> |
| |
| #include "base/base_export.h" |
| #include "base/message_loop/message_pump_type.h" |
| #include "base/process/process_handle.h" |
| #include "base/threading/platform_thread_ref.h" |
| #include "base/time/time.h" |
| #include "base/trace_event/base_tracing_forward.h" |
| #include "base/types/strong_alias.h" |
| #include "build/build_config.h" |
| |
| #if BUILDFLAG(IS_WIN) |
| #include "base/win/windows_types.h" |
| #elif BUILDFLAG(IS_FUCHSIA) |
| #include <zircon/types.h> |
| #elif BUILDFLAG(IS_POSIX) |
| #include <pthread.h> |
| #include <unistd.h> |
| #endif |
| |
| #if BUILDFLAG(IS_CHROMEOS) |
| #include "base/feature_list.h" |
| #endif |
| |
| namespace base { |
| |
| // Used for uniquely identifying a thread. |
| // |
| // Wraps a platform-specific integer value with platform-specific size, |
| // guaranteed to have a maximum bitness of 64-bit. Getting a 32-bit value is |
| // possible only if we either know the platform-specific size (because we're in |
| // platform-specific code), or if we are ok with truncation of the value (e.g. |
| // because we are logging and the occasional false match is not catastrophic). |
| class BASE_EXPORT PlatformThreadId { |
| public: |
| #if BUILDFLAG(IS_WIN) |
| using UnderlyingType = DWORD; |
| #elif BUILDFLAG(IS_FUCHSIA) |
| using UnderlyingType = zx_koid_t; |
| #elif BUILDFLAG(IS_APPLE) |
| using UnderlyingType = uint64_t; |
| #elif BUILDFLAG(IS_POSIX) |
| using UnderlyingType = pid_t; |
| #endif |
| static_assert(std::is_integral_v<UnderlyingType>, "Always an integer value."); |
| |
| constexpr PlatformThreadId() = default; |
| |
| // Special templated constructor which prevents implicit conversion of the |
| // integer argument. |
| template <typename T> |
| explicit constexpr PlatformThreadId(T value) |
| requires(std::is_same_v<T, UnderlyingType>) |
| : value_(value) {} |
| |
| static constexpr PlatformThreadId ForTest(int value) { |
| return PlatformThreadId(static_cast<UnderlyingType>(value)); |
| } |
| |
| // Allow conversion to u/int64_t, whether the underlying type is signed or |
| // not, and whether it is 32-bit or 64-bit. |
| explicit constexpr operator uint64_t() const { |
| static_assert(sizeof(uint64_t) >= sizeof(UnderlyingType)); |
| return static_cast<uint64_t>(value_); |
| } |
| explicit constexpr operator int64_t() const { |
| static_assert(sizeof(int64_t) >= sizeof(UnderlyingType)); |
| return static_cast<int64_t>(value_); |
| } |
| // Forbid conversion to u/int32_t, since we might have a 64-bit |
| // value -- use truncate_to_int32_for_display_only() or raw() instead. |
| explicit constexpr operator uint32_t() const = delete; |
| explicit constexpr operator int32_t() const = delete; |
| |
| // Truncating getter for an int32 representation of the id. |
| // |
| // AVOID: This should only be used in cases where truncation is not |
| // catastrophic, e.g. displaying the thread id in traces or logs. It will |
| // always be preferable to display the full, untruncated thread id. |
| constexpr int32_t truncate_to_int32_for_display_only() const { |
| return static_cast<int32_t>(value_); |
| } |
| |
| // Getter for the underlying raw value. Should only be used when |
| // exposing the UnderlyingType, e.g. passing into system APIs or passing into |
| // functions overloaded on different integer sizes like NumberToString. |
| constexpr UnderlyingType raw() const { return value_; } |
| |
| constexpr friend auto operator<=>(const PlatformThreadId& lhs, |
| const PlatformThreadId& rhs) = default; |
| constexpr friend bool operator==(const PlatformThreadId& lhs, |
| const PlatformThreadId& rhs) = default; |
| |
| // Allow serialising into a trace. |
| void WriteIntoTrace(perfetto::TracedValue&& context) const; |
| |
| private: |
| // TODO(crbug.com/393384253): Use a system-specific invalid value, which might |
| // be 0, -1, or some other value from a system header. |
| UnderlyingType value_ = 0; |
| }; |
| |
| inline std::ostream& operator<<(std::ostream& stream, |
| const PlatformThreadId& id) { |
| return stream << id.raw(); |
| } |
| |
| // Used to operate on threads. |
| class PlatformThreadHandle { |
| public: |
| #if BUILDFLAG(IS_WIN) |
| typedef void* Handle; |
| #elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) |
| typedef pthread_t Handle; |
| #endif |
| |
| constexpr PlatformThreadHandle() : handle_(0) {} |
| |
| explicit constexpr PlatformThreadHandle(Handle handle) : handle_(handle) {} |
| |
| bool is_equal(const PlatformThreadHandle& other) const { |
| return handle_ == other.handle_; |
| } |
| |
| bool is_null() const { return !handle_; } |
| |
| Handle platform_handle() const { return handle_; } |
| |
| private: |
| Handle handle_; |
| }; |
| |
| static constexpr PlatformThreadId kInvalidThreadId = PlatformThreadId(); |
| |
| // Valid values for `thread_type` of Thread::Options, SimpleThread::Options, |
| // and SetCurrentThreadType(), listed in increasing order of importance. |
| // |
| // It is up to each platform-specific implementation what these translate to. |
| // Callers should avoid setting different ThreadTypes on different platforms |
| // (ifdefs) at all cost, instead the platform differences should be encoded in |
| // the platform-specific implementations. Some implementations may treat |
| // adjacent ThreadTypes in this enum as equivalent. |
| // |
| // Reach out to //base/task/OWNERS (scheduler-dev@chromium.org) before changing |
| // thread type assignments in your component, as such decisions affect the whole |
| // of Chrome. |
| // |
| // Refer to PlatformThreadTest.SetCurrentThreadTypeTest in |
| // platform_thread_unittest.cc for the most up-to-date state of each platform's |
| // handling of ThreadType. |
| enum class ThreadType : int { |
| // Suitable for threads that have the least urgency and lowest priority, and |
| // can be interrupted or delayed by other types. |
| kBackground, |
| // Suitable for threads that are less important than normal type, and can be |
| // interrupted or delayed by threads with kDefault type. |
| kUtility, |
| // Suitable for threads that produce user-visible artifacts but aren't |
| // latency sensitive. The underlying platform will try to be economic |
| // in its usage of resources for this thread, if possible. |
| kResourceEfficient, |
| // Default type. The thread priority or quality of service will be set to |
| // platform default. In Chrome, this is suitable for handling user |
| // interactions (input), only display and audio can get a higher priority. |
| kDefault, |
| // Suitable for display critical threads, ie. threads critical to compositing |
| // and presenting the foreground content. |
| kDisplayCritical, |
| // Suitable for low-latency, glitch-resistant audio. |
| kRealtimeAudio, |
| kMaxValue = kRealtimeAudio, |
| }; |
| |
| // Cross-platform mapping of physical thread priorities. Used by tests to verify |
| // the underlying effects of SetCurrentThreadType. |
| enum class ThreadPriorityForTest : int { |
| kBackground, |
| kUtility, |
| kResourceEfficient, |
| kNormal, |
| kCompositing, |
| kDisplay, |
| kRealtimeAudio, |
| kMaxValue = kRealtimeAudio, |
| }; |
| |
| // A namespace for low-level thread functions. |
| class BASE_EXPORT PlatformThreadBase { |
| public: |
| // Implement this interface to run code on a background thread. Your |
| // ThreadMain method will be called on the newly created thread. |
| class BASE_EXPORT Delegate { |
| public: |
| virtual void ThreadMain() = 0; |
| |
| #if BUILDFLAG(IS_APPLE) |
| // TODO: Move this to the PlatformThreadApple class. |
| // The interval at which the thread expects to have work to do. Zero if |
| // unknown. (Example: audio buffer duration for real-time audio.) Is used to |
| // optimize the thread real-time behavior. Is called on the newly created |
| // thread before ThreadMain(). |
| virtual TimeDelta GetRealtimePeriod(); |
| #endif |
| |
| protected: |
| virtual ~Delegate() = default; |
| }; |
| |
| PlatformThreadBase() = delete; |
| PlatformThreadBase(const PlatformThreadBase&) = delete; |
| PlatformThreadBase& operator=(const PlatformThreadBase&) = delete; |
| |
| // Gets the current thread id, which may be useful for logging purposes. |
| static PlatformThreadId CurrentId(); |
| |
| // Gets the current thread reference, which can be used to check if |
| // we're on the right thread quickly. |
| static PlatformThreadRef CurrentRef(); |
| |
| // Get the handle representing the current thread. On Windows, this is a |
| // pseudo handle constant which will always represent the thread using it and |
| // hence should not be shared with other threads nor be used to differentiate |
| // the current thread from another. |
| static PlatformThreadHandle CurrentHandle(); |
| |
| // Yield the current thread so another thread can be scheduled. |
| // |
| // Note: this is likely not the right call to make in most situations. If this |
| // is part of a spin loop, consider base::Lock, which likely has better tail |
| // latency. Yielding the thread has different effects depending on the |
| // platform, system load, etc., and can result in yielding the CPU for less |
| // than 1us, or many tens of ms. |
| static void YieldCurrentThread(); |
| |
| // Sleeps for the specified duration (real-time; ignores time overrides). |
| // Note: The sleep duration may be in base::Time or base::TimeTicks, depending |
| // on platform. If you're looking to use this in unit tests testing delayed |
| // tasks, this will be unreliable - instead, use |
| // base::test::TaskEnvironment with MOCK_TIME mode. |
| static void Sleep(base::TimeDelta duration); |
| |
| // Sets the thread name visible to debuggers/tools. This will try to |
| // initialize the context for current thread unless it's a WorkerThread. |
| static void SetName(const std::string& name); |
| |
| // Gets the thread name, if previously set by SetName. |
| static const char* GetName(); |
| |
| // Creates a new thread. The `stack_size` parameter can be 0 to indicate |
| // that the default stack size should be used. Upon success, |
| // `*thread_handle` will be assigned a handle to the newly created thread, |
| // and `delegate`'s ThreadMain method will be executed on the newly created |
| // thread. |
| // NOTE: When you are done with the thread handle, you must call Join to |
| // release system resources associated with the thread. You must ensure that |
| // the Delegate object outlives the thread. |
| static bool Create(size_t stack_size, |
| Delegate* delegate, |
| PlatformThreadHandle* thread_handle) { |
| return CreateWithType(stack_size, delegate, thread_handle, |
| ThreadType::kDefault); |
| } |
| |
| // CreateWithType() does the same thing as Create() except the priority and |
| // possibly the QoS of the thread is set based on `thread_type`. |
| // `pump_type_hint` must be provided if the thread will be using a |
| // MessagePumpForUI or MessagePumpForIO as this affects the application of |
| // `thread_type`. |
| static bool CreateWithType( |
| size_t stack_size, |
| Delegate* delegate, |
| PlatformThreadHandle* thread_handle, |
| ThreadType thread_type, |
| MessagePumpType pump_type_hint = MessagePumpType::DEFAULT); |
| |
| // CreateNonJoinable() does the same thing as Create() except the thread |
| // cannot be Join()'d. Therefore, it also does not output a |
| // PlatformThreadHandle. |
| static bool CreateNonJoinable(size_t stack_size, Delegate* delegate); |
| |
| // CreateNonJoinableWithType() does the same thing as CreateNonJoinable() |
| // except the type of the thread is set based on `type`. `pump_type_hint` must |
| // be provided if the thread will be using a MessagePumpForUI or |
| // MessagePumpForIO as this affects the application of `thread_type`. |
| static bool CreateNonJoinableWithType( |
| size_t stack_size, |
| Delegate* delegate, |
| ThreadType thread_type, |
| MessagePumpType pump_type_hint = MessagePumpType::DEFAULT); |
| |
| // Joins with a thread created via the Create function. This function blocks |
| // the caller until the designated thread exits. This will invalidate |
| // `thread_handle`. |
| static void Join(PlatformThreadHandle thread_handle); |
| |
| // Detaches and releases the thread handle. The thread is no longer joinable |
| // and `thread_handle` is invalidated after this call. |
| static void Detach(PlatformThreadHandle thread_handle); |
| |
| // Returns true if SetCurrentThreadType() should be able to change the type |
| // of a thread in current process from `from` to `to`. |
| static bool CanChangeThreadType(ThreadType from, ThreadType to); |
| |
| // Declares the type of work running on the current thread. This will affect |
| // things like thread priority and thread QoS (Quality of Service) to the best |
| // of the current platform's abilities. |
| static void SetCurrentThreadType(ThreadType thread_type); |
| |
| // Get the last `thread_type` set by SetCurrentThreadType, no matter if the |
| // underlying priority successfully changed or not. |
| static ThreadType GetCurrentThreadType(); |
| |
| // Returns a realtime period provided by `delegate`. |
| static TimeDelta GetRealtimePeriod(Delegate* delegate); |
| |
| // Returns the override of task leeway if any. |
| static std::optional<TimeDelta> GetThreadLeewayOverride(); |
| |
| // Returns the default thread stack size set by chrome. If we do not |
| // explicitly set default size then returns 0. |
| static size_t GetDefaultThreadStackSize(); |
| |
| static ThreadPriorityForTest GetCurrentThreadPriorityForTest(); |
| |
| protected: |
| static void SetNameCommon(const std::string& name); |
| }; |
| |
| #if BUILDFLAG(IS_APPLE) |
| class BASE_EXPORT PlatformThreadApple : public PlatformThreadBase { |
| public: |
| // Stores the period value in TLS. |
| static void SetCurrentThreadRealtimePeriodValue(TimeDelta realtime_period); |
| |
| static TimeDelta GetCurrentThreadRealtimePeriodForTest(); |
| |
| // Initializes features for this class. See `base::features::Init()`. |
| static void InitializeFeatures(); |
| }; |
| #endif // BUILDFLAG(IS_APPLE) |
| |
| #if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) |
| class ThreadTypeDelegate; |
| using IsViaIPC = base::StrongAlias<class IsViaIPCTag, bool>; |
| |
| class BASE_EXPORT PlatformThreadLinux : public PlatformThreadBase { |
| public: |
| static constexpr struct sched_param kRealTimeAudioPrio = {8}; |
| static constexpr struct sched_param kRealTimeDisplayPrio = {6}; |
| |
| // Sets a delegate which handles thread type changes for this process. This |
| // must be externally synchronized with any call to SetCurrentThreadType. |
| static void SetThreadTypeDelegate(ThreadTypeDelegate* delegate); |
| |
| // Toggles a specific thread's type at runtime. This can be used to |
| // change the priority of a thread in a different process and will fail |
| // if the calling process does not have proper permissions. The |
| // SetCurrentThreadType() function above is preferred in favor of |
| // security but on platforms where sandboxed processes are not allowed to |
| // change priority this function exists to allow a non-sandboxed process |
| // to change the priority of sandboxed threads for improved performance. |
| // Warning: Don't use this for a main thread because that will change the |
| // whole thread group's (i.e. process) priority. |
| static void SetThreadType(ProcessId process_id, |
| PlatformThreadId thread_id, |
| ThreadType thread_type, |
| IsViaIPC via_ipc); |
| |
| // For a given thread id and thread type, setup the cpuset and schedtune |
| // CGroups for the thread. |
| static void SetThreadCgroupsForThreadType(PlatformThreadId thread_id, |
| ThreadType thread_type); |
| |
| // Determine if thread_id is a background thread by looking up whether |
| // it is in the urgent or non-urgent cpuset |
| static bool IsThreadBackgroundedForTest(PlatformThreadId thread_id); |
| }; |
| #endif // BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) |
| |
| #if BUILDFLAG(IS_CHROMEOS) |
| BASE_EXPORT BASE_DECLARE_FEATURE(kSetRtForDisplayThreads); |
| |
| class CrossProcessPlatformThreadDelegate; |
| |
| class BASE_EXPORT PlatformThreadChromeOS : public PlatformThreadLinux { |
| public: |
| // Sets a delegate which handles thread type changes for threads of another |
| // process. This must be externally synchronized with any call to |
| // SetCurrentThreadType. |
| static void SetCrossProcessPlatformThreadDelegate( |
| CrossProcessPlatformThreadDelegate* delegate); |
| |
| // Initializes features for this class. See `base::features::Init()`. |
| static void InitializeFeatures(); |
| |
| // Toggles a specific thread's type at runtime. This is the ChromeOS-specific |
| // version and includes Linux's functionality but does slightly more. See |
| // PlatformThreadLinux's SetThreadType() header comment for Linux details. |
| static void SetThreadType(ProcessId process_id, |
| PlatformThreadId thread_id, |
| ThreadType thread_type, |
| IsViaIPC via_ipc); |
| |
| // Returns true if the feature for backgrounding of threads is enabled. |
| static bool IsThreadsBgFeatureEnabled(); |
| |
| // Returns true if the feature for setting display threads to RT is enabled. |
| static bool IsDisplayThreadsRtFeatureEnabled(); |
| |
| // Set a specific thread as backgrounded. This is called when the process |
| // moves to and from the background and changes have to be made to each of its |
| // thread's scheduling attributes. |
| static void SetThreadBackgrounded(ProcessId process_id, |
| PlatformThreadId thread_id, |
| bool backgrounded); |
| |
| // Returns the thread type of a thread given its thread id. |
| static std::optional<ThreadType> GetThreadTypeFromThreadId( |
| ProcessId process_id, |
| PlatformThreadId thread_id); |
| |
| // DCHECKs that the caller is on the correct sequence to perform cross-process |
| // priority changes without races. |
| // |
| // This does not simply return a `SequenceChecker&` and let the caller do the |
| // check, because doing so requires an `#include` of sequence_checker.h (since |
| // `SequenceChecker` is an alias rather than a forward-declarable class), |
| // which complicates life for other base/ headers trying to avoid circular |
| // dependencies. |
| static void DcheckCrossProcessThreadPrioritySequence(); |
| }; |
| #endif // BUILDFLAG(IS_CHROMEOS) |
| |
| // Alias to the correct platform-specific class based on preprocessor directives |
| #if BUILDFLAG(IS_APPLE) |
| using PlatformThread = PlatformThreadApple; |
| #elif BUILDFLAG(IS_CHROMEOS) |
| using PlatformThread = PlatformThreadChromeOS; |
| #elif BUILDFLAG(IS_LINUX) |
| using PlatformThread = PlatformThreadLinux; |
| #else |
| using PlatformThread = PlatformThreadBase; |
| #endif |
| |
| namespace internal { |
| |
| void SetCurrentThreadType(ThreadType thread_type, |
| MessagePumpType pump_type_hint); |
| |
| void SetCurrentThreadTypeImpl(ThreadType thread_type, |
| MessagePumpType pump_type_hint); |
| |
| #if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) |
| void SetThreadTypeLinux(ProcessId process_id, |
| PlatformThreadId thread_id, |
| ThreadType thread_type, |
| IsViaIPC via_ipc); |
| #endif |
| #if BUILDFLAG(IS_CHROMEOS) |
| void SetThreadTypeChromeOS(ProcessId process_id, |
| PlatformThreadId thread_id, |
| ThreadType thread_type, |
| IsViaIPC via_ipc); |
| #endif |
| #if BUILDFLAG(IS_CHROMEOS) |
| inline constexpr auto SetThreadType = SetThreadTypeChromeOS; |
| #elif BUILDFLAG(IS_LINUX) |
| inline constexpr auto SetThreadType = SetThreadTypeLinux; |
| #endif |
| |
| } // namespace internal |
| |
| } // namespace base |
| |
| #endif // BASE_THREADING_PLATFORM_THREAD_H_ |