1//===-- condition_variable_linux.cpp ----------------------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "platform.h"
10
11#if SCUDO_LINUX
12
13#include "condition_variable_linux.h"
14
15#include "atomic_helpers.h"
16
17#include <limits.h>
18#include <linux/futex.h>
19#include <sys/syscall.h>
20#include <unistd.h>
21
22namespace scudo {
23
24void ConditionVariableLinux::notifyAllImpl(UNUSED HybridMutex &M) {
25 const u32 V = atomic_load_relaxed(A: &Counter);
26 atomic_store_relaxed(A: &Counter, V: V + 1);
27
28 // TODO(chiahungduan): Move the waiters from the futex waiting queue
29 // `Counter` to futex waiting queue `M` so that the awoken threads won't be
30 // blocked again due to locked `M` by current thread.
31 if (LastNotifyAll != V) {
32 syscall(SYS_futex, reinterpret_cast<uptr>(&Counter), FUTEX_WAKE_PRIVATE,
33 INT_MAX, nullptr, nullptr, 0);
34 }
35
36 LastNotifyAll = V + 1;
37}
38
39void ConditionVariableLinux::waitImpl(HybridMutex &M) {
40 const u32 V = atomic_load_relaxed(A: &Counter) + 1;
41 atomic_store_relaxed(A: &Counter, V);
42
43 // TODO: Use ScopedUnlock when it's supported.
44 M.unlock();
45 syscall(SYS_futex, reinterpret_cast<uptr>(&Counter), FUTEX_WAIT_PRIVATE, V,
46 nullptr, nullptr, 0);
47 M.lock();
48}
49
50} // namespace scudo
51
52#endif // SCUDO_LINUX
53