libc/src/pthread/pthread_spin_init.cpp

   1 //===-- Implementation of pthread_spin_init function ----------------------===//
   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 "src/pthread/pthread_spin_init.h"
  10 #include "hdr/errno_macros.h"
  11 #include "src/__support/CPP/new.h"
  12 #include "src/__support/common.h"
  13 #include "src/__support/threads/spin_lock.h"
  14 #include <pthread.h> // for PTHREAD_PROCESS_SHARED, PTHREAD_PROCESS_PRIVATE
  15
  16 namespace LIBC_NAMESPACE_DECL {
  17
  18 static_assert(sizeof(pthread_spinlock_t::__lockword) == sizeof(SpinLock) &&
  19                   alignof(decltype(pthread_spinlock_t::__lockword)) ==
  20                       alignof(SpinLock),
  21               "pthread_spinlock_t::__lockword and SpinLock must be of the same "
  22               "size and alignment");
  23
  24 LLVM_LIBC_FUNCTION(int, pthread_spin_init,
  25                    (pthread_spinlock_t * lock, [[maybe_unused]] int pshared)) {
  26   if (!lock)
  27     return EINVAL;
  28   if (pshared != PTHREAD_PROCESS_SHARED && pshared != PTHREAD_PROCESS_PRIVATE)
  29     return EINVAL;
  30   // The spin lock here is a simple atomic flag, so we don't need to do any
  31   // special handling for pshared.
  32   ::new (&lock->__lockword) SpinLock();
  33   lock->__owner = 0;
  34   return 0;
  35 }
  36
  37 } // namespace LIBC_NAMESPACE_DECL