1//===-- Implementation of pthread_spin_lock 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_lock.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
15namespace LIBC_NAMESPACE_DECL {
16
17static_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
23LLVM_LIBC_FUNCTION(int, pthread_spin_lock, (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->is_invalid())
32 return EINVAL;
33
34 pid_t self_tid = internal::gettid();
35 // If an implementation detects that the value specified by the lock argument
36 // to pthread_spin_lock() refers to a spin lock object for which the calling
37 // thread already holds the lock, it is recommended that the function should
38 // fail and report an [EDEADLK] error.
39 if (lock->__owner == self_tid)
40 return EDEADLK;
41
42 spin_lock->lock();
43 lock->__owner = self_tid;
44 return 0;
45}
46
47} // namespace LIBC_NAMESPACE_DECL
48

source code of libc/src/pthread/pthread_spin_lock.cpp