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