LCOV - code coverage report
Current view: top level - include/llvm/Support - RWMutex.h (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 22 30 73.3 %
Date: 2017-09-14 15:23:50 Functions: 4 4 100.0 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : //===- RWMutex.h - Reader/Writer Mutual Exclusion Lock ----------*- C++ -*-===//
       2             : //
       3             : //                     The LLVM Compiler Infrastructure
       4             : //
       5             : // This file is distributed under the University of Illinois Open Source
       6             : // License. See LICENSE.TXT for details.
       7             : //
       8             : //===----------------------------------------------------------------------===//
       9             : //
      10             : // This file declares the llvm::sys::RWMutex class.
      11             : //
      12             : //===----------------------------------------------------------------------===//
      13             : 
      14             : #ifndef LLVM_SUPPORT_RWMUTEX_H
      15             : #define LLVM_SUPPORT_RWMUTEX_H
      16             : 
      17             : #include "llvm/Config/llvm-config.h"
      18             : #include "llvm/Support/Threading.h"
      19             : #include <cassert>
      20             : 
      21             : namespace llvm {
      22             : namespace sys {
      23             : 
      24             :     /// @brief Platform agnostic RWMutex class.
      25             :     class RWMutexImpl
      26             :     {
      27             :     /// @name Constructors
      28             :     /// @{
      29             :     public:
      30             : 
      31             :       /// Initializes the lock but doesn't acquire it.
      32             :       /// @brief Default Constructor.
      33             :       explicit RWMutexImpl();
      34             : 
      35             :     /// @}
      36             :     /// @name Do Not Implement
      37             :     /// @{
      38             :       RWMutexImpl(const RWMutexImpl & original) = delete;
      39             :       RWMutexImpl &operator=(const RWMutexImpl &) = delete;
      40             :     /// @}
      41             : 
      42             :       /// Releases and removes the lock
      43             :       /// @brief Destructor
      44             :       ~RWMutexImpl();
      45             : 
      46             :     /// @}
      47             :     /// @name Methods
      48             :     /// @{
      49             :     public:
      50             : 
      51             :       /// Attempts to unconditionally acquire the lock in reader mode. If the
      52             :       /// lock is held by a writer, this method will wait until it can acquire
      53             :       /// the lock.
      54             :       /// @returns false if any kind of error occurs, true otherwise.
      55             :       /// @brief Unconditionally acquire the lock in reader mode.
      56             :       bool reader_acquire();
      57             : 
      58             :       /// Attempts to release the lock in reader mode.
      59             :       /// @returns false if any kind of error occurs, true otherwise.
      60             :       /// @brief Unconditionally release the lock in reader mode.
      61             :       bool reader_release();
      62             : 
      63             :       /// Attempts to unconditionally acquire the lock in reader mode. If the
      64             :       /// lock is held by any readers, this method will wait until it can
      65             :       /// acquire the lock.
      66             :       /// @returns false if any kind of error occurs, true otherwise.
      67             :       /// @brief Unconditionally acquire the lock in writer mode.
      68             :       bool writer_acquire();
      69             : 
      70             :       /// Attempts to release the lock in writer mode.
      71             :       /// @returns false if any kind of error occurs, true otherwise.
      72             :       /// @brief Unconditionally release the lock in write mode.
      73             :       bool writer_release();
      74             : 
      75             :     //@}
      76             :     /// @name Platform Dependent Data
      77             :     /// @{
      78             :     private:
      79             : #if defined(LLVM_ENABLE_THREADS) && LLVM_ENABLE_THREADS != 0
      80             :       void* data_ = nullptr; ///< We don't know what the data will be
      81             : #endif
      82             :     };
      83             : 
      84             :     /// SmartMutex - An R/W mutex with a compile time constant parameter that
      85             :     /// indicates whether this mutex should become a no-op when we're not
      86             :     /// running in multithreaded mode.
      87             :     template<bool mt_only>
      88       64083 :     class SmartRWMutex {
      89             :       RWMutexImpl impl;
      90             :       unsigned readers = 0;
      91             :       unsigned writers = 0;
      92             : 
      93             :     public:
      94      590250 :       explicit SmartRWMutex() = default;
      95             :       SmartRWMutex(const SmartRWMutex<mt_only> & original) = delete;
      96             :       SmartRWMutex<mt_only> &operator=(const SmartRWMutex<mt_only> &) = delete;
      97             : 
      98     7281992 :       bool lock_shared() {
      99     7281992 :         if (!mt_only || llvm_is_multithreaded())
     100     8945151 :           return impl.reader_acquire();
     101             : 
     102             :         // Single-threaded debugging code.  This would be racy in multithreaded
     103             :         // mode, but provides not sanity checks in single threaded mode.
     104           0 :         ++readers;
     105           0 :         return true;
     106             :       }
     107             : 
     108     7281998 :       bool unlock_shared() {
     109     7281998 :         if (!mt_only || llvm_is_multithreaded())
     110     8945165 :           return impl.reader_release();
     111             : 
     112             :         // Single-threaded debugging code.  This would be racy in multithreaded
     113             :         // mode, but provides not sanity checks in single threaded mode.
     114             :         assert(readers > 0 && "Reader lock not acquired before release!");
     115           0 :         --readers;
     116           0 :         return true;
     117             :       }
     118             : 
     119    12294154 :       bool lock() {
     120    12294154 :         if (!mt_only || llvm_is_multithreaded())
     121    13120832 :           return impl.writer_acquire();
     122             : 
     123             :         // Single-threaded debugging code.  This would be racy in multithreaded
     124             :         // mode, but provides not sanity checks in single threaded mode.
     125             :         assert(writers == 0 && "Writer lock already acquired!");
     126           0 :         ++writers;
     127           0 :         return true;
     128             :       }
     129             : 
     130    12294154 :       bool unlock() {
     131    12294154 :         if (!mt_only || llvm_is_multithreaded())
     132    13120832 :           return impl.writer_release();
     133             : 
     134             :         // Single-threaded debugging code.  This would be racy in multithreaded
     135             :         // mode, but provides not sanity checks in single threaded mode.
     136             :         assert(writers == 1 && "Writer lock not acquired before release!");
     137           0 :         --writers;
     138           0 :         return true;
     139             :       }
     140             :     };
     141             : 
     142             :     typedef SmartRWMutex<false> RWMutex;
     143             : 
     144             :     /// ScopedReader - RAII acquisition of a reader lock
     145             :     template<bool mt_only>
     146             :     struct SmartScopedReader {
     147             :       SmartRWMutex<mt_only>& mutex;
     148             : 
     149     8945152 :       explicit SmartScopedReader(SmartRWMutex<mt_only>& m) : mutex(m) {
     150    10608317 :         mutex.lock_shared();
     151             :       }
     152             : 
     153             :       ~SmartScopedReader() {
     154    10608341 :         mutex.unlock_shared();
     155     8945169 :       }
     156             :     };
     157             : 
     158             :     typedef SmartScopedReader<false> ScopedReader;
     159             : 
     160             :     /// ScopedWriter - RAII acquisition of a writer lock
     161             :     template<bool mt_only>
     162             :     struct SmartScopedWriter {
     163             :       SmartRWMutex<mt_only>& mutex;
     164             : 
     165    13120832 :       explicit SmartScopedWriter(SmartRWMutex<mt_only>& m) : mutex(m) {
     166    13947510 :         mutex.lock();
     167             :       }
     168             : 
     169             :       ~SmartScopedWriter() {
     170    13947510 :         mutex.unlock();
     171    13120832 :       }
     172             :     };
     173             : 
     174             :     typedef SmartScopedWriter<false> ScopedWriter;
     175             : 
     176             : } // end namespace sys
     177             : } // end namespace llvm
     178             : 
     179             : #endif // LLVM_SUPPORT_RWMUTEX_H

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