compiler-rt/lib/scudo/standalone/condition_variable_linux.cpp

   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
  22 namespace scudo {
  23
  24 void ConditionVariableLinux::notifyAllImpl(UNUSED HybridMutex &M) {
  25   const u32 V = atomic_load_relaxed(&Counter);
  26   atomic_store_relaxed(&Counter, 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
  39 void ConditionVariableLinux::waitImpl(HybridMutex &M) {
  40   const u32 V = atomic_load_relaxed(&Counter) + 1;
  41   atomic_store_relaxed(&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