xref: /aosp_15_r20/external/scudo/standalone/condition_variable_linux.cpp (revision 76559068c068bd27e82aff38fac3bfc865233bca)
1*76559068SAndroid Build Coastguard Worker //===-- condition_variable_linux.cpp ----------------------------*- C++ -*-===//
2*76559068SAndroid Build Coastguard Worker //
3*76559068SAndroid Build Coastguard Worker // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4*76559068SAndroid Build Coastguard Worker // See https://llvm.org/LICENSE.txt for license information.
5*76559068SAndroid Build Coastguard Worker // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6*76559068SAndroid Build Coastguard Worker //
7*76559068SAndroid Build Coastguard Worker //===----------------------------------------------------------------------===//
8*76559068SAndroid Build Coastguard Worker 
9*76559068SAndroid Build Coastguard Worker #include "platform.h"
10*76559068SAndroid Build Coastguard Worker 
11*76559068SAndroid Build Coastguard Worker #if SCUDO_LINUX
12*76559068SAndroid Build Coastguard Worker 
13*76559068SAndroid Build Coastguard Worker #include "condition_variable_linux.h"
14*76559068SAndroid Build Coastguard Worker 
15*76559068SAndroid Build Coastguard Worker #include "atomic_helpers.h"
16*76559068SAndroid Build Coastguard Worker 
17*76559068SAndroid Build Coastguard Worker #include <limits.h>
18*76559068SAndroid Build Coastguard Worker #include <linux/futex.h>
19*76559068SAndroid Build Coastguard Worker #include <sys/syscall.h>
20*76559068SAndroid Build Coastguard Worker #include <unistd.h>
21*76559068SAndroid Build Coastguard Worker 
22*76559068SAndroid Build Coastguard Worker namespace scudo {
23*76559068SAndroid Build Coastguard Worker 
notifyAllImpl(UNUSED HybridMutex & M)24*76559068SAndroid Build Coastguard Worker void ConditionVariableLinux::notifyAllImpl(UNUSED HybridMutex &M) {
25*76559068SAndroid Build Coastguard Worker   const u32 V = atomic_load_relaxed(&Counter);
26*76559068SAndroid Build Coastguard Worker   atomic_store_relaxed(&Counter, V + 1);
27*76559068SAndroid Build Coastguard Worker 
28*76559068SAndroid Build Coastguard Worker   // TODO(chiahungduan): Move the waiters from the futex waiting queue
29*76559068SAndroid Build Coastguard Worker   // `Counter` to futex waiting queue `M` so that the awoken threads won't be
30*76559068SAndroid Build Coastguard Worker   // blocked again due to locked `M` by current thread.
31*76559068SAndroid Build Coastguard Worker   if (LastNotifyAll != V) {
32*76559068SAndroid Build Coastguard Worker     syscall(SYS_futex, reinterpret_cast<uptr>(&Counter), FUTEX_WAKE_PRIVATE,
33*76559068SAndroid Build Coastguard Worker             INT_MAX, nullptr, nullptr, 0);
34*76559068SAndroid Build Coastguard Worker   }
35*76559068SAndroid Build Coastguard Worker 
36*76559068SAndroid Build Coastguard Worker   LastNotifyAll = V + 1;
37*76559068SAndroid Build Coastguard Worker }
38*76559068SAndroid Build Coastguard Worker 
waitImpl(HybridMutex & M)39*76559068SAndroid Build Coastguard Worker void ConditionVariableLinux::waitImpl(HybridMutex &M) {
40*76559068SAndroid Build Coastguard Worker   const u32 V = atomic_load_relaxed(&Counter) + 1;
41*76559068SAndroid Build Coastguard Worker   atomic_store_relaxed(&Counter, V);
42*76559068SAndroid Build Coastguard Worker 
43*76559068SAndroid Build Coastguard Worker   // TODO: Use ScopedUnlock when it's supported.
44*76559068SAndroid Build Coastguard Worker   M.unlock();
45*76559068SAndroid Build Coastguard Worker   syscall(SYS_futex, reinterpret_cast<uptr>(&Counter), FUTEX_WAIT_PRIVATE, V,
46*76559068SAndroid Build Coastguard Worker           nullptr, nullptr, 0);
47*76559068SAndroid Build Coastguard Worker   M.lock();
48*76559068SAndroid Build Coastguard Worker }
49*76559068SAndroid Build Coastguard Worker 
50*76559068SAndroid Build Coastguard Worker } // namespace scudo
51*76559068SAndroid Build Coastguard Worker 
52*76559068SAndroid Build Coastguard Worker #endif // SCUDO_LINUX
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