52 lines
1.5 KiB
C++
52 lines
1.5 KiB
C++
//===-- condition_variable_linux.cpp ----------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "platform.h"
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#if SCUDO_LINUX
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#include "condition_variable_linux.h"
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#include "atomic_helpers.h"
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#include <limits.h>
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#include <linux/futex.h>
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#include <sys/syscall.h>
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#include <unistd.h>
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namespace scudo {
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void ConditionVariableLinux::notifyAllImpl(UNUSED HybridMutex &M) {
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const u32 V = atomic_load_relaxed(&Counter);
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atomic_store_relaxed(&Counter, V + 1);
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// TODO(chiahungduan): Move the waiters from the futex waiting queue
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// `Counter` to futex waiting queue `M` so that the awoken threads won't be
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// blocked again due to locked `M` by current thread.
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if (LastNotifyAll != V) {
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syscall(SYS_futex, reinterpret_cast<uptr>(&Counter), FUTEX_WAKE_PRIVATE,
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INT_MAX, nullptr, nullptr, 0);
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}
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LastNotifyAll = V + 1;
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}
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void ConditionVariableLinux::waitImpl(HybridMutex &M) {
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const u32 V = atomic_load_relaxed(&Counter) + 1;
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atomic_store_relaxed(&Counter, V);
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// TODO: Use ScopedUnlock when it's supported.
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M.unlock();
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syscall(SYS_futex, reinterpret_cast<uptr>(&Counter), FUTEX_WAIT_PRIVATE, V,
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nullptr, nullptr, 0);
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M.lock();
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}
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} // namespace scudo
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#endif // SCUDO_LINUX
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