libc/src/__support/threads/CndVar.h

   1 //===-- A platform independent abstraction layer for cond vars --*- 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___SUPPORT_SRC_THREADS_LINUX_CNDVAR_H
  10 #define LLVM_LIBC___SUPPORT_SRC_THREADS_LINUX_CNDVAR_H
  11
  12 #include "src/__support/macros/config.h"
  13 #include "src/__support/threads/linux/futex_utils.h" // Futex
  14 #include "src/__support/threads/linux/raw_mutex.h"   // RawMutex
  15 #include "src/__support/threads/mutex.h"             // Mutex
  16
  17 #include <stdint.h> // uint32_t
  18
  19 namespace LIBC_NAMESPACE_DECL {
  20
  21 class CndVar {
  22   enum CndWaiterStatus : uint32_t {
  23     WS_Waiting = 0xE,
  24     WS_Signalled = 0x5,
  25   };
  26
  27   struct CndWaiter {
  28     Futex futex_word = WS_Waiting;
  29     CndWaiter *next = nullptr;
  30   };
  31
  32   CndWaiter *waitq_front;
  33   CndWaiter *waitq_back;
  34   RawMutex qmtx;
  35
  36 public:
  37   LIBC_INLINE static int init(CndVar *cv) {
  38     cv->waitq_front = cv->waitq_back = nullptr;
  39     RawMutex::init(&cv->qmtx);
  40     return 0;
  41   }
  42
  43   LIBC_INLINE static void destroy(CndVar *cv) {
  44     cv->waitq_front = cv->waitq_back = nullptr;
  45   }
  46
  47   // Returns 0 on success, -1 on error.
  48   int wait(Mutex *m);
  49   void notify_one();
  50   void broadcast();
  51 };
  52
  53 } // namespace LIBC_NAMESPACE_DECL
  54
  55 #endif // LLVM_LIBC_SRC___SUPPORT_THREADS_LINUX_CNDVAR_H