libc/src/pthread/pthread_spin_trylock.cpp

   1 //===-- Implementation of pthread_spin_trylock 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_trylock.h"
  10 #include "hdr/errno_macros.h"
  11 #include "src/__support/common.h"
  12 #include "src/__support/threads/identifier.h"
  13 #include "src/__support/threads/spin_lock.h"
  14
  15 namespace LIBC_NAMESPACE_DECL {
  16
  17 static_assert(sizeof(pthread_spinlock_t::__lockword) == sizeof(SpinLock) &&
  18                   alignof(decltype(pthread_spinlock_t::__lockword)) ==
  19                       alignof(SpinLock),
  20               "pthread_spinlock_t::__lockword and SpinLock must be of the same "
  21               "size and alignment");
  22
  23 LLVM_LIBC_FUNCTION(int, pthread_spin_trylock, (pthread_spinlock_t * lock)) {
  24   // If an implementation detects that the value specified by the lock argument
  25   // to pthread_spin_lock() or pthread_spin_trylock() does not refer to an
  26   // initialized spin lock object, it is recommended that the function should
  27   // fail and report an [EINVAL] error.
  28   if (!lock)
  29     return EINVAL;
  30   auto spin_lock = reinterpret_cast<SpinLock *>(&lock->__lockword);
  31   if (!spin_lock || spin_lock->is_invalid())
  32     return EINVAL;
  33   // Try to acquire the lock without blocking.
  34   if (!spin_lock->try_lock())
  35     return EBUSY;
  36   // We have acquired the lock. Update the owner field.
  37   lock->__owner = internal::gettid();
  38   return 0;
  39 }
  40
  41 } // namespace LIBC_NAMESPACE_DECL