0b1639581a
When single-threaded mode is selected, all instances of the keyword `LIBC_THREAD_LOCAL` are stubbed out, similar to how it currently works on the GPU. This allows baremetal builds to avoid using thread_local. However, libcxx uses shared headers, so we need to be careful there. Thankfully, there is already an option to disable multithreading in libcxx, so a flag is added such that single-threaded mode is propagated down to libc.
74 lines
2.7 KiB
C++
74 lines
2.7 KiB
C++
//===--- A platform independent abstraction layer for mutexes ---*- C++ -*-===//
|
|
//
|
|
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
|
|
// See https://llvm.org/LICENSE.txt for license information.
|
|
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#ifndef LLVM_LIBC_SRC___SUPPORT_THREADS_MUTEX_H
|
|
#define LLVM_LIBC_SRC___SUPPORT_THREADS_MUTEX_H
|
|
|
|
#include "src/__support/macros/attributes.h"
|
|
#include "src/__support/macros/config.h"
|
|
|
|
#if LIBC_THREAD_MODE == LIBC_THREAD_MODE_PLATFORM
|
|
|
|
// Platform independent code will include this header file which pulls
|
|
// the platform specific specializations using platform macros.
|
|
//
|
|
// The platform specific specializations should define a class by name
|
|
// Mutex with non-static methods having the following signature:
|
|
//
|
|
// MutexError lock();
|
|
// MutexError trylock();
|
|
// MutexError timedlock(...);
|
|
// MutexError unlock();
|
|
// MutexError reset(); // Used to reset inconsistent robust mutexes.
|
|
//
|
|
// Apart from the above non-static methods, the specializations should
|
|
// also provide few static methods with the following signature:
|
|
//
|
|
// static MutexError init(mtx_t *);
|
|
// static MutexError destroy(mtx_t *);
|
|
//
|
|
// All of the static and non-static methods should ideally be implemented
|
|
// as inline functions so that implementations of public functions can
|
|
// call them without a function call overhead.
|
|
//
|
|
// Another point to keep in mind that is that the libc internally needs a
|
|
// few global locks. So, to avoid static initialization order fiasco, we
|
|
// want the constructors of the Mutex classes to be constexprs.
|
|
|
|
#if defined(__linux__)
|
|
#include "src/__support/threads/linux/mutex.h"
|
|
#endif // __linux__
|
|
|
|
#elif LIBC_THREAD_MODE == LIBC_THREAD_MODE_SINGLE
|
|
|
|
#include "src/__support/threads/mutex_common.h"
|
|
|
|
namespace LIBC_NAMESPACE_DECL {
|
|
|
|
/// Implementation of a simple passthrough mutex which guards nothing. A
|
|
/// complete Mutex locks in general cannot be implemented on the GPU, or on some
|
|
/// baremetal platforms. We simply define the Mutex interface and require that
|
|
/// only a single thread executes code requiring a mutex lock.
|
|
struct Mutex {
|
|
LIBC_INLINE constexpr Mutex(bool, bool, bool, bool) {}
|
|
|
|
LIBC_INLINE MutexError lock() { return MutexError::NONE; }
|
|
LIBC_INLINE MutexError unlock() { return MutexError::NONE; }
|
|
LIBC_INLINE MutexError reset() { return MutexError::NONE; }
|
|
};
|
|
|
|
} // namespace LIBC_NAMESPACE_DECL
|
|
|
|
#elif LIBC_THREAD_MODE == LIBC_THREAD_MODE_EXTERNAL
|
|
|
|
// TODO: Implement the interfacing, if necessary, e.g. "extern struct Mutex;"
|
|
|
|
#endif // LIBC_THREAD_MODE == LIBC_THREAD_MODE_PLATFORM
|
|
|
|
#endif // LLVM_LIBC_SRC___SUPPORT_THREADS_MUTEX_H
|