libc/src/__support/threads/mutex.h

   1 //===--- A platform independent abstraction layer for mutexes ---*- 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 #ifndef LLVM_LIBC_SRC_SUPPORT_THREAD_MUTEX_H
  10 #define LLVM_LIBC_SRC_SUPPORT_THREAD_MUTEX_H
  11
  12 #include "src/__support/macros/properties/architectures.h"
  13
  14 // Platform independent code will include this header file which pulls
  15 // the platfrom specific specializations using platform macros.
  16 //
  17 // The platform specific specializations should define a class by name
  18 // Mutex with non-static methods having the following signature:
  19 //
  20 // MutexError lock();
  21 // MutexError trylock();
  22 // MutexError timedlock(...);
  23 // MutexError unlock();
  24 // MutexError reset(); // Used to reset inconsistent robust mutexes.
  25 //
  26 // Apart from the above non-static methods, the specializations should
  27 // also provide few static methods with the following signature:
  28 //
  29 // static MutexError init(mtx_t *);
  30 // static MutexError destroy(mtx_t *);
  31 //
  32 // All of the static and non-static methods should ideally be implemented
  33 // as inline functions so that implementations of public functions can
  34 // call them without a function call overhead.
  35 //
  36 // Another point to keep in mind that is that the libc internally needs a
  37 // few global locks. So, to avoid static initialization order fiasco, we
  38 // want the constructors of the Mutex classes to be constexprs.
  39
  40 #if defined(__unix__)
  41 #include "linux/mutex.h"
  42 #elif defined(LIBC_TARGET_ARCH_IS_GPU)
  43 #include "gpu/mutex.h"
  44 #endif // __unix__
  45
  46 namespace __llvm_libc {
  47
  48 // An RAII class for easy locking and unlocking of mutexes.
  49 class MutexLock {
  50   Mutex *mutex;
  51
  52 public:
  53   explicit MutexLock(Mutex *m) : mutex(m) { mutex->lock(); }
  54
  55   ~MutexLock() { mutex->unlock(); }
  56 };
  57
  58 } // namespace __llvm_libc
  59
  60 #endif // LLVM_LIBC_SRC_SUPPORT_THREAD_MUTEX_H