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Diffstat (limited to '')
| -rw-r--r-- | js/src/builtin/AtomicsObject.h | 141 |
1 files changed, 141 insertions, 0 deletions
diff --git a/js/src/builtin/AtomicsObject.h b/js/src/builtin/AtomicsObject.h new file mode 100644 index 0000000000..0f2e6c4af9 --- /dev/null +++ b/js/src/builtin/AtomicsObject.h @@ -0,0 +1,141 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- + * vim: set ts=8 sts=2 et sw=2 tw=80: + * This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#ifndef builtin_AtomicsObject_h +#define builtin_AtomicsObject_h + +#include "mozilla/Maybe.h" +#include "mozilla/TimeStamp.h" + +#include "threading/ConditionVariable.h" +#include "threading/ProtectedData.h" // js::ThreadData +#include "vm/NativeObject.h" + +namespace js { + +class SharedArrayRawBuffer; + +class AtomicsObject : public NativeObject { + public: + static const JSClass class_; +}; + +class FutexThread { + friend class AutoLockFutexAPI; + + public: + [[nodiscard]] static bool initialize(); + static void destroy(); + + static void lock(); + static void unlock(); + + FutexThread(); + [[nodiscard]] bool initInstance(); + void destroyInstance(); + + // Parameters to notify(). + enum NotifyReason { + NotifyExplicit, // Being asked to wake up by another thread + NotifyForJSInterrupt // Interrupt requested + }; + + // Result codes from wait() and atomics_wait_impl(). + enum class WaitResult { + Error, // Error has been reported, just propagate error signal + NotEqual, // Did not wait because the values differed + OK, // Waited and was woken + TimedOut // Waited and timed out + }; + + // Block the calling thread and wait. + // + // The futex lock must be held around this call. + // + // The timeout is the number of milliseconds, with fractional + // times allowed; specify mozilla::Nothing() for an indefinite + // wait. + // + // wait() will not wake up spuriously. + [[nodiscard]] WaitResult wait( + JSContext* cx, js::UniqueLock<js::Mutex>& locked, + const mozilla::Maybe<mozilla::TimeDuration>& timeout); + + // Notify the thread this is associated with. + // + // The futex lock must be held around this call. (The sleeping + // thread will not wake up until the caller of Atomics.notify() + // releases the lock.) + // + // If the thread is not waiting then this method does nothing. + // + // If the thread is waiting in a call to wait() and the + // reason is NotifyExplicit then the wait() call will return + // with Woken. + // + // If the thread is waiting in a call to wait() and the + // reason is NotifyForJSInterrupt then the wait() will return + // with WaitingNotifiedForInterrupt; in the latter case the caller + // of wait() must handle the interrupt. + void notify(NotifyReason reason); + + bool isWaiting(); + + // If canWait() returns false (the default) then wait() is disabled + // on the thread to which the FutexThread belongs. + bool canWait() { return canWait_; } + + void setCanWait(bool flag) { canWait_ = flag; } + + private: + enum FutexState { + Idle, // We are not waiting or woken + Waiting, // We are waiting, nothing has happened yet + WaitingNotifiedForInterrupt, // We are waiting, but have been interrupted, + // and have not yet started running the + // interrupt handler + WaitingInterrupted, // We are waiting, but have been interrupted + // and are running the interrupt handler + Woken // Woken by a script call to Atomics.notify + }; + + // Condition variable that this runtime will wait on. + js::ConditionVariable* cond_; + + // Current futex state for this runtime. When not in a wait this + // is Idle; when in a wait it is Waiting or the reason the futex + // is about to wake up. + FutexState state_; + + // Shared futex lock for all runtimes. We can perhaps do better, + // but any lock will need to be per-domain (consider SharedWorker) + // or coarser. + static mozilla::Atomic<js::Mutex*, mozilla::SequentiallyConsistent> lock_; + + // A flag that controls whether waiting is allowed. + ThreadData<bool> canWait_; +}; + +// Go to sleep if the int32_t value at the given address equals `value`. +[[nodiscard]] FutexThread::WaitResult atomics_wait_impl( + JSContext* cx, SharedArrayRawBuffer* sarb, size_t byteOffset, int32_t value, + const mozilla::Maybe<mozilla::TimeDuration>& timeout); + +// Go to sleep if the int64_t value at the given address equals `value`. +[[nodiscard]] FutexThread::WaitResult atomics_wait_impl( + JSContext* cx, SharedArrayRawBuffer* sarb, size_t byteOffset, int64_t value, + const mozilla::Maybe<mozilla::TimeDuration>& timeout); + +// Notify some waiters on the given address. If `count` is negative then notify +// all. The return value is nonnegative and is the number of waiters woken. If +// the number of waiters woken exceeds INT64_MAX then this never returns. If +// `count` is nonnegative then the return value is never greater than `count`. +[[nodiscard]] int64_t atomics_notify_impl(SharedArrayRawBuffer* sarb, + size_t byteOffset, int64_t count); + +} /* namespace js */ + +#endif /* builtin_AtomicsObject_h */ |