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	* MSan added with fixes for libc++ * libc++ sepatare build * add libc++ to ci * libstdc++ in CI * libcpp and msan to external projects * std::sqrt * awful_hack(ci): install whole llvm instead of libc++ in terrible way for test containers * Adding ddeb packages for teststages and repos * libc++ more for test container * save some money on debug * colored coredumps * revert ci * chore(ci): collect asan ubsan and libc++ build with mtr and regression status ignored
		
			
				
	
	
		
			721 lines
		
	
	
		
			19 KiB
		
	
	
	
		
			C++
		
	
	
	
	
	
			
		
		
	
	
			721 lines
		
	
	
		
			19 KiB
		
	
	
	
		
			C++
		
	
	
	
	
	
/* Copyright (C) 2014 InfiniDB, Inc.
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   This program is free software; you can redistribute it and/or
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   modify it under the terms of the GNU General Public License
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   as published by the Free Software Foundation; version 2 of
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   the License.
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   This program is distributed in the hope that it will be useful,
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   but WITHOUT ANY WARRANTY; without even the implied warranty of
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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   GNU General Public License for more details.
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   You should have received a copy of the GNU General Public License
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   along with this program; if not, write to the Free Software
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   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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   MA 02110-1301, USA. */
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/*****************************************************************************
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 * $Id$
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 *
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 ****************************************************************************/
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#include <unistd.h>
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#include <iostream>
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#include <stdexcept>
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#include <string>
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#include <sstream>
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#include <iomanip>
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#include <unordered.h>
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#ifndef NDEBUG
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#define NDEBUG
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#endif
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#include <cassert>
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using namespace std;
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#include <boost/thread/thread.hpp>
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#include <boost/date_time/posix_time/posix_time.hpp>
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#include <boost/interprocess/shared_memory_object.hpp>
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#include <boost/interprocess/sync/named_semaphore.hpp>
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#include <boost/version.hpp>
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namespace bi = boost::interprocess;
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#define RWLOCK_DLLEXPORT
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#include "rwlock.h"
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#undef RWLOCK_DLLEXPORT
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using namespace boost::posix_time;
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#include "shmkeys.h"
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#include "installdir.h"
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namespace
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{
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using namespace rwlock;
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// This mutex needs to be fully instantiated by the runtime static object
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// init mechanism or the lock in makeRWLockShmImpl() will fail
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boost::mutex instanceMapMutex;
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typedef std::tr1::unordered_map<int, RWLockShmImpl*> LockMap_t;
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// Windows doesn't init static objects the same as Linux, so make this a ptr
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LockMap_t* lockMapPtr = 0;
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}  // namespace
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namespace rwlock
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{
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#if defined(DEBUG) && !defined(_MSC_VER)
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#define RWLOCK_DEBUG
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#endif
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#ifdef RWLOCK_DEBUG
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#define PRINTSTATE()                                                      \
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  cerr << "  reading = " << fPImpl->fState->reading << endl               \
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       << "  writing = " << fPImpl->fState->writing << endl               \
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       << "  readerswaiting = " << fPImpl->fState->readerswaiting << endl \
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       << "  writerswaiting = " << fPImpl->fState->writerswaiting << endl
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#define CHECKSAFETY()                                                                           \
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  do                                                                                            \
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  {                                                                                             \
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    if (!((fPImpl->fState->reading == 0 &&                                                      \
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           (fPImpl->fState->writing == 0 || fPImpl->fState->writing == 1)) ||                   \
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          (fPImpl->fState->reading > 0 && fPImpl->fState->writing == 0)))                       \
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    {                                                                                           \
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      cerr << __PRETTY_FUNCTION__ << ":" << __LINE__ << ": safety invariant violation" << endl; \
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      PRINTSTATE();                                                                             \
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      throw std::logic_error("RWLock: safety invariant violation");                             \
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    }                                                                                           \
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  } while (0)
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#define CHECKLIVENESS()                                                                           \
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  do                                                                                              \
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  {                                                                                               \
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    if (!((!(fPImpl->fState->readerswaiting > 0 || fPImpl->fState->writerswaiting > 0) ||         \
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           (fPImpl->fState->reading > 0 || fPImpl->fState->writing > 0)) ||                       \
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          (!(fPImpl->fState->reading == 0 && fPImpl->fState->writing == 0) ||                     \
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           (fPImpl->fState->readerswaiting == 0 && fPImpl->fState->writerswaiting == 0))))        \
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						|
    {                                                                                             \
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      cerr << __PRETTY_FUNCTION__ << ":" << __LINE__ << ": liveness invariant violation" << endl; \
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      PRINTSTATE();                                                                               \
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      throw std::logic_error("RWLock: liveness invariant violation");                             \
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    }                                                                                             \
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  } while (0)
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#else
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#define PRINTSTATE() (void)0
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#define CHECKSAFETY() (void)0
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#define CHECKLIVENESS() (void)0
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#endif
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/*static*/
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RWLockShmImpl* RWLockShmImpl::makeRWLockShmImpl(int key, bool* excl)
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{
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  boost::mutex::scoped_lock lk(instanceMapMutex);
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  LockMap_t::iterator iter;
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						|
  if (!lockMapPtr)
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    lockMapPtr = new LockMap_t();
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						|
  iter = lockMapPtr->find(key);
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						|
  if (iter == lockMapPtr->end())
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						|
  {
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						|
    RWLockShmImpl* ptr = 0;
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						|
    bool bExcl = excl ? *excl : false;
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    ptr = new RWLockShmImpl(key, bExcl);
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    lockMapPtr->insert(make_pair(key, ptr));
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    return ptr;
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						|
  }
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						|
  else if (excl)
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						|
  {
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    *excl = false;  // This isn't the first time for this lock.
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  }
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						|
  return iter->second;
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}
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RWLockShmImpl::RWLockShmImpl(int key, bool excl)
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{
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						|
  string keyName = BRM::ShmKeys::keyToName(key);
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						|
  fKeyString = keyName;
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						|
  try
 | 
						|
  {
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						|
    bi::permissions perms;
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						|
    perms.set_unrestricted();
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						|
    bi::shared_memory_object shm(bi::create_only, keyName.c_str(), bi::read_write, perms);
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						|
    shm.truncate(sizeof(struct State));
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    fStateShm.swap(shm);
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						|
    bi::mapped_region region(fStateShm, bi::read_write);
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						|
    fRegion.swap(region);
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						|
    fState = static_cast<State*>(fRegion.get_address());
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    fState->writerswaiting = 0;
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    fState->readerswaiting = 0;
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    fState->reading = 0;
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						|
    if (excl)
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      fState->writing = 1;
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    else
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						|
      fState->writing = 0;
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						|
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						|
    new (&fState->sems[RWLock::MUTEX]) bi::interprocess_semaphore(1);
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						|
    new (&fState->sems[RWLock::READERS]) bi::interprocess_semaphore(0);
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						|
    new (&fState->sems[RWLock::WRITERS]) bi::interprocess_semaphore(0);
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						|
  }
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						|
  catch (bi::interprocess_exception& e)
 | 
						|
  {
 | 
						|
    if (e.get_error_code() == bi::security_error)
 | 
						|
    {
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						|
      cerr << "RWLock:  Failed to create the lock.  Check perms on /dev/shm; should be 1777" << endl;
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						|
      throw;
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						|
    }
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						|
    if (e.get_error_code() == bi::already_exists_error && excl)
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      throw not_excl();
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						|
    if (e.get_error_code() != bi::already_exists_error)
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      throw;
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						|
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						|
    try
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						|
    {
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						|
      bi::shared_memory_object shm(bi::open_only, keyName.c_str(), bi::read_write);
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						|
      fStateShm.swap(shm);
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						|
    }
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    catch (exception& e)
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    {
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						|
      cerr << "RWLock failed to attach to the " << keyName << " shared mem segment, got " << e.what() << endl;
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      throw;
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    }
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						|
    bi::mapped_region region(fStateShm, bi::read_write);
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    fRegion.swap(region);
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    fState = static_cast<State*>(fRegion.get_address());
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  }
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  catch (...)
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  {
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    runtime_error rex("RWLockShmImpl::RWLockShmImpl(): caught unknown exception");
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    cerr << rex.what() << endl;
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    throw rex;
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  }
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}
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RWLock::RWLock(int key, bool* excl)
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{
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  fPImpl = RWLockShmImpl::makeRWLockShmImpl(key, excl);
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}
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RWLock::~RWLock()
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{
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}
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void RWLock::down(int num, bool block)
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{
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again:
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  try
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  {
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    if (block)
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      fPImpl->fState->sems[num].wait();
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    else
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    {
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      bool gotIt = fPImpl->fState->sems[num].try_wait();
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      if (!gotIt)
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        throw wouldblock();
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    }
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  }
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  catch (bi::interprocess_exception& bipe)
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  {
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    ostringstream os;
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    os << "RWLock::down(): caught boost ipe: " << bipe.what() << " key = " << fPImpl->keyString()
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       << " error code = " << bipe.get_error_code();
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    if (bipe.get_error_code() == 1)  // it passes through EINTR apparently
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      goto again;
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    runtime_error rex(os.str());
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    cerr << bipe.what() << endl;
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    throw rex;
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  }
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  catch (std::exception& ex)
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  {
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    cerr << __PRETTY_FUNCTION__ << ":" << __LINE__ << ": caught an exception: " << ex.what() << endl;
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    throw;
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  }
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						|
  catch (...)
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  {
 | 
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    cerr << __PRETTY_FUNCTION__ << ":" << __LINE__ << ": caught an exception" << endl;
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    throw runtime_error("RWLock::down(): caught an exception");
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  }
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}
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bool RWLock::timed_down(int num, const ptime& delay)
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{
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  bool gotTheLock = false;
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  //	cout << "timed_down: current time = " << to_simple_string(microsec_clock::local_time()) <<
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  //			"  wake time = " << to_simple_string(delay) << endl;
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again:
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 | 
						|
  try
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  {
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    // I don't think I've seen timed_wait() ever wait, need to do this 'manually'
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    // gotTheLock = fPImpl->fState->sems[num].timed_wait(delay);
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    do
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    {
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      gotTheLock = fPImpl->fState->sems[num].try_wait();
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 | 
						|
      if (!gotTheLock)
 | 
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        usleep(100000);
 | 
						|
    } while (!gotTheLock && microsec_clock::local_time() < delay);
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  }
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						|
  catch (boost::thread_interrupted&)
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  {
 | 
						|
    // no need to do anything here
 | 
						|
  }
 | 
						|
  catch (bi::interprocess_exception& bipe)
 | 
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  {
 | 
						|
    ostringstream os;
 | 
						|
    os << "RWLock::timed_down(): caught boost ipe: " << bipe.what() << " key = " << fPImpl->keyString()
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       << " error code = " << bipe.get_error_code();
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 | 
						|
    if (bipe.get_error_code() == 1)  // it passes through EINTR apparently
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      goto again;
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 | 
						|
    runtime_error rex(os.str());
 | 
						|
    cerr << bipe.what() << endl;
 | 
						|
    throw rex;
 | 
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  }
 | 
						|
  catch (std::exception& ex)
 | 
						|
  {
 | 
						|
    cerr << __PRETTY_FUNCTION__ << ":" << __LINE__ << ": caught an exception: " << ex.what() << endl;
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						|
    throw;
 | 
						|
  }
 | 
						|
  catch (...)
 | 
						|
  {
 | 
						|
    cerr << __PRETTY_FUNCTION__ << ":" << __LINE__ << ": caught an exception" << endl;
 | 
						|
    throw runtime_error("RWLock::timed_down(): caught an exception");
 | 
						|
  }
 | 
						|
 | 
						|
  return gotTheLock;
 | 
						|
}
 | 
						|
 | 
						|
void RWLock::up(int num)
 | 
						|
{
 | 
						|
  try
 | 
						|
  {
 | 
						|
    fPImpl->fState->sems[num].post();
 | 
						|
  }
 | 
						|
  catch (bi::interprocess_exception& bipe)
 | 
						|
  {
 | 
						|
    ostringstream os;
 | 
						|
    os << "RWLock::up(): caught boost ipe: " << bipe.what() << " key = " << fPImpl->keyString();
 | 
						|
    runtime_error rex(os.str());
 | 
						|
    cerr << bipe.what() << endl;
 | 
						|
    throw rex;
 | 
						|
  }
 | 
						|
  catch (...)
 | 
						|
  {
 | 
						|
    throw runtime_error("RWLock::up(): caught an exception");
 | 
						|
  }
 | 
						|
}
 | 
						|
 | 
						|
void RWLock::read_lock(bool block)
 | 
						|
{
 | 
						|
  down(MUTEX, true);
 | 
						|
  CHECKSAFETY();
 | 
						|
  CHECKLIVENESS();
 | 
						|
 | 
						|
  if (fPImpl->fState->writerswaiting > 0 || fPImpl->fState->writing > 0)
 | 
						|
  {
 | 
						|
    if (!block)
 | 
						|
    {
 | 
						|
      up(MUTEX);
 | 
						|
      throw wouldblock();
 | 
						|
    }
 | 
						|
 | 
						|
    fPImpl->fState->readerswaiting++;
 | 
						|
    CHECKSAFETY();
 | 
						|
    CHECKLIVENESS();
 | 
						|
    up(MUTEX);
 | 
						|
    down(READERS);  // unblocked by write_unlock();
 | 
						|
#ifdef RWLOCK_DEBUG
 | 
						|
    down(MUTEX, true);
 | 
						|
    CHECKSAFETY();
 | 
						|
    CHECKLIVENESS();
 | 
						|
    up(MUTEX);
 | 
						|
#endif
 | 
						|
  }
 | 
						|
  else
 | 
						|
  {
 | 
						|
    fPImpl->fState->reading++;
 | 
						|
 | 
						|
    CHECKSAFETY();
 | 
						|
    CHECKLIVENESS();
 | 
						|
    up(MUTEX);
 | 
						|
  }
 | 
						|
}
 | 
						|
 | 
						|
void RWLock::read_lock_priority(bool block)
 | 
						|
{
 | 
						|
  down(MUTEX, true);
 | 
						|
  CHECKSAFETY();
 | 
						|
  CHECKLIVENESS();
 | 
						|
 | 
						|
  if (fPImpl->fState->writing > 0)
 | 
						|
  {
 | 
						|
    if (!block)
 | 
						|
    {
 | 
						|
      up(MUTEX);
 | 
						|
      throw wouldblock();
 | 
						|
    }
 | 
						|
 | 
						|
    fPImpl->fState->readerswaiting++;
 | 
						|
    CHECKSAFETY();
 | 
						|
    CHECKLIVENESS();
 | 
						|
    up(MUTEX);
 | 
						|
    down(READERS);  // unblocked by write_unlock();
 | 
						|
#ifdef RWLOCK_DEBUG
 | 
						|
    down(MUTEX, true);
 | 
						|
    CHECKSAFETY();
 | 
						|
    CHECKLIVENESS();
 | 
						|
    up(MUTEX);
 | 
						|
#endif
 | 
						|
  }
 | 
						|
  else
 | 
						|
  {
 | 
						|
    fPImpl->fState->reading++;
 | 
						|
 | 
						|
    CHECKSAFETY();
 | 
						|
    CHECKLIVENESS();
 | 
						|
    up(MUTEX);
 | 
						|
  }
 | 
						|
}
 | 
						|
 | 
						|
void RWLock::read_unlock()
 | 
						|
{
 | 
						|
  down(MUTEX, true);
 | 
						|
  CHECKSAFETY();
 | 
						|
  CHECKLIVENESS();
 | 
						|
 | 
						|
  /* Made this a bit more tolerant of errors b/c the lock recovery code can technically
 | 
						|
   * be wrong.  In the practically zero chance that happens, better to take the chance
 | 
						|
   * on a read race than a sure assertion failure
 | 
						|
   */
 | 
						|
  if (fPImpl->fState->reading > 0)
 | 
						|
  {
 | 
						|
    --fPImpl->fState->reading;
 | 
						|
 | 
						|
    if (fPImpl->fState->writerswaiting > 0 && fPImpl->fState->reading == 0)
 | 
						|
    {
 | 
						|
      --fPImpl->fState->writerswaiting;
 | 
						|
      fPImpl->fState->writing++;
 | 
						|
      up(WRITERS);
 | 
						|
    }
 | 
						|
  }
 | 
						|
 | 
						|
  CHECKSAFETY();
 | 
						|
  CHECKLIVENESS();
 | 
						|
  up(MUTEX);
 | 
						|
}
 | 
						|
 | 
						|
void RWLock::write_lock(bool block)
 | 
						|
{
 | 
						|
  down(MUTEX, true);
 | 
						|
  CHECKSAFETY();
 | 
						|
  CHECKLIVENESS();
 | 
						|
 | 
						|
  if (fPImpl->fState->writing > 0 || fPImpl->fState->reading > 0)
 | 
						|
  {
 | 
						|
    if (!block)
 | 
						|
    {
 | 
						|
      up(MUTEX);
 | 
						|
      throw wouldblock();
 | 
						|
    }
 | 
						|
 | 
						|
    fPImpl->fState->writerswaiting++;
 | 
						|
    CHECKSAFETY();
 | 
						|
    CHECKLIVENESS();
 | 
						|
    up(MUTEX);
 | 
						|
    down(WRITERS);  // unblocked by write_unlock() or read_unlock()
 | 
						|
#ifdef RWLOCK_DEBUG
 | 
						|
    down(MUTEX, true);
 | 
						|
    CHECKSAFETY();
 | 
						|
    CHECKLIVENESS();
 | 
						|
    up(MUTEX);
 | 
						|
#endif
 | 
						|
  }
 | 
						|
  else
 | 
						|
  {
 | 
						|
    fPImpl->fState->writing++;
 | 
						|
 | 
						|
    CHECKSAFETY();
 | 
						|
    CHECKLIVENESS();
 | 
						|
    up(MUTEX);
 | 
						|
  }
 | 
						|
}
 | 
						|
 | 
						|
// this exists only for the sake of code cleanup
 | 
						|
#define RETURN_STATE(mutex_state, state)                    \
 | 
						|
  if (state)                                                \
 | 
						|
  {                                                         \
 | 
						|
    state->mutexLocked = mutex_state;                       \
 | 
						|
    state->readerswaiting = fPImpl->fState->readerswaiting; \
 | 
						|
    state->reading = fPImpl->fState->reading;               \
 | 
						|
    state->writerswaiting = fPImpl->fState->writerswaiting; \
 | 
						|
    state->writing = fPImpl->fState->writing;               \
 | 
						|
  }
 | 
						|
 | 
						|
bool RWLock::timed_write_lock(const struct timespec& ts, struct LockState* state)
 | 
						|
{
 | 
						|
  bool gotIt, gotIt2;
 | 
						|
  ptime delay;
 | 
						|
 | 
						|
  delay = microsec_clock::local_time() + seconds(ts.tv_sec) + microsec(ts.tv_nsec / 1000);
 | 
						|
 | 
						|
  gotIt = timed_down(MUTEX, delay);
 | 
						|
 | 
						|
  if (!gotIt)
 | 
						|
  {
 | 
						|
    RETURN_STATE(true, state)
 | 
						|
    return false;
 | 
						|
  }
 | 
						|
 | 
						|
  CHECKSAFETY();
 | 
						|
  CHECKLIVENESS();
 | 
						|
 | 
						|
  if (fPImpl->fState->writing > 0 || fPImpl->fState->reading > 0)
 | 
						|
  {
 | 
						|
    fPImpl->fState->writerswaiting++;
 | 
						|
 | 
						|
    CHECKSAFETY();
 | 
						|
    CHECKLIVENESS();
 | 
						|
    up(MUTEX);
 | 
						|
    gotIt = timed_down(WRITERS, delay);
 | 
						|
 | 
						|
    if (!gotIt)
 | 
						|
    {
 | 
						|
      // need to grab the mutex again to revoke the lock request
 | 
						|
      // need to adjust the timeout value to make sure the attempt is made.
 | 
						|
      delay = microsec_clock::local_time() + seconds(10);
 | 
						|
      gotIt2 = timed_down(MUTEX, delay);
 | 
						|
 | 
						|
      if (!gotIt2)
 | 
						|
      {
 | 
						|
        RETURN_STATE(true, state);
 | 
						|
        return false;
 | 
						|
      }
 | 
						|
 | 
						|
      /* This thread could have been granted the write lock during that second
 | 
						|
         lock grab attempt.  Observation: the thread that granted it up'd the writers sem,
 | 
						|
         but didn't wake this thread.  If there were other writers waiting, one of those
 | 
						|
         woke.  At this point, if writerswaiting > 0, this thread should consider itself
 | 
						|
         one that's still waiting and should back out of the request.
 | 
						|
         If writerswaiting == 0, this thread was the one granted the write lock, and
 | 
						|
         needs to take possession.
 | 
						|
       */
 | 
						|
      if (fPImpl->fState->writerswaiting == 0)
 | 
						|
      {
 | 
						|
        try
 | 
						|
        {
 | 
						|
          down(WRITERS, false);
 | 
						|
        }
 | 
						|
        catch (const wouldblock&)
 | 
						|
        {
 | 
						|
          // Somehow another writer was able to jump in front.  This is "impossible".
 | 
						|
          RETURN_STATE(false, state);
 | 
						|
          up(MUTEX);
 | 
						|
          return false;
 | 
						|
        }
 | 
						|
 | 
						|
        up(MUTEX);
 | 
						|
        return true;
 | 
						|
      }
 | 
						|
 | 
						|
      fPImpl->fState->writerswaiting--;
 | 
						|
 | 
						|
      // need to unblock whatever was blocked by this lock attempt
 | 
						|
      if (fPImpl->fState->writing == 0 && fPImpl->fState->writerswaiting == 0)
 | 
						|
      {
 | 
						|
        fPImpl->fState->reading += fPImpl->fState->readerswaiting;
 | 
						|
 | 
						|
        while (fPImpl->fState->readerswaiting > 0)
 | 
						|
        {
 | 
						|
          --fPImpl->fState->readerswaiting;
 | 
						|
          up(READERS);
 | 
						|
        }
 | 
						|
      }
 | 
						|
 | 
						|
      // else if there's an active writer, do nothing
 | 
						|
 | 
						|
      CHECKSAFETY();
 | 
						|
      CHECKLIVENESS();
 | 
						|
      RETURN_STATE(false, state);
 | 
						|
      up(MUTEX);
 | 
						|
      return false;
 | 
						|
    }
 | 
						|
    else
 | 
						|
      return true;
 | 
						|
  }
 | 
						|
  else
 | 
						|
  {
 | 
						|
    fPImpl->fState->writing++;
 | 
						|
    CHECKSAFETY();
 | 
						|
    CHECKLIVENESS();
 | 
						|
    up(MUTEX);
 | 
						|
    return true;
 | 
						|
  }
 | 
						|
}
 | 
						|
 | 
						|
void RWLock::write_unlock()
 | 
						|
{
 | 
						|
  down(MUTEX, true);
 | 
						|
  CHECKSAFETY();
 | 
						|
  CHECKLIVENESS();
 | 
						|
 | 
						|
  assert(fPImpl->fState->writing > 0);
 | 
						|
  --fPImpl->fState->writing;
 | 
						|
 | 
						|
  if (fPImpl->fState->writerswaiting > 0)
 | 
						|
  {
 | 
						|
    --fPImpl->fState->writerswaiting;
 | 
						|
    fPImpl->fState->writing++;
 | 
						|
    up(WRITERS);
 | 
						|
  }
 | 
						|
  else if (fPImpl->fState->readerswaiting > 0)
 | 
						|
  {
 | 
						|
    // let up to state->readerswaiting readers go
 | 
						|
 | 
						|
    fPImpl->fState->reading = fPImpl->fState->readerswaiting;
 | 
						|
 | 
						|
    while (fPImpl->fState->readerswaiting > 0)
 | 
						|
    {
 | 
						|
      --fPImpl->fState->readerswaiting;
 | 
						|
      up(READERS);
 | 
						|
    }
 | 
						|
  }
 | 
						|
 | 
						|
  CHECKSAFETY();
 | 
						|
  CHECKLIVENESS();
 | 
						|
  up(MUTEX);
 | 
						|
}
 | 
						|
 | 
						|
void RWLock::upgrade_to_write()
 | 
						|
{
 | 
						|
  down(MUTEX, true);
 | 
						|
  CHECKSAFETY();
 | 
						|
  CHECKLIVENESS();
 | 
						|
 | 
						|
  /* Made this a bit more tolerant of errors b/c the lock recovery code can technically
 | 
						|
   * be wrong.  In the practically zero chance that happens, better to take the chance
 | 
						|
   * on a read race than a sure assertion failure
 | 
						|
   */
 | 
						|
  if (fPImpl->fState->reading > 0)
 | 
						|
  {
 | 
						|
    --fPImpl->fState->reading;
 | 
						|
 | 
						|
    // try to cut in line
 | 
						|
    // On entry we hold a read lock, so reading > 0, and at this point, reading >= 0
 | 
						|
    if (fPImpl->fState->reading == 0)
 | 
						|
    {
 | 
						|
      fPImpl->fState->writing++;
 | 
						|
      CHECKSAFETY();
 | 
						|
      CHECKLIVENESS();
 | 
						|
      up(MUTEX);
 | 
						|
      return;
 | 
						|
    }
 | 
						|
  }
 | 
						|
 | 
						|
  // cut & paste from write_lock()
 | 
						|
  // The invariants hold that, on entry, writing == 0 and, by now, reading > 0, so this branch is always taken
 | 
						|
  if (fPImpl->fState->writing > 0 || fPImpl->fState->reading > 0)
 | 
						|
  {
 | 
						|
    fPImpl->fState->writerswaiting++;
 | 
						|
 | 
						|
    CHECKSAFETY();
 | 
						|
    CHECKLIVENESS();
 | 
						|
    up(MUTEX);
 | 
						|
    down(WRITERS, true);  // unblocked by write_unlock() or read_unlock()
 | 
						|
#ifdef RWLOCK_DEBUG
 | 
						|
    down(MUTEX, true);
 | 
						|
    CHECKSAFETY();
 | 
						|
    CHECKLIVENESS();
 | 
						|
    up(MUTEX);
 | 
						|
#endif
 | 
						|
  }
 | 
						|
  else  // don't think we can get here: reading > 0 && writing == 0 && reading == 0
 | 
						|
  {
 | 
						|
    fPImpl->fState->writing++;
 | 
						|
 | 
						|
    CHECKSAFETY();
 | 
						|
    CHECKLIVENESS();
 | 
						|
    up(MUTEX);
 | 
						|
  }
 | 
						|
}
 | 
						|
 | 
						|
/* It's safe (and necessary) to simply convert this writer to a reader without
 | 
						|
 blocking */
 | 
						|
void RWLock::downgrade_to_read()
 | 
						|
{
 | 
						|
  down(MUTEX, true);
 | 
						|
  CHECKSAFETY();
 | 
						|
  CHECKLIVENESS();
 | 
						|
  assert(fPImpl->fState->writing > 0);
 | 
						|
  --fPImpl->fState->writing;
 | 
						|
 | 
						|
  if (fPImpl->fState->readerswaiting > 0)
 | 
						|
  {
 | 
						|
    // let up to state->readerswaiting readers go
 | 
						|
    fPImpl->fState->reading = fPImpl->fState->readerswaiting;
 | 
						|
 | 
						|
    while (fPImpl->fState->readerswaiting > 0)
 | 
						|
    {
 | 
						|
      --fPImpl->fState->readerswaiting;
 | 
						|
      up(READERS);
 | 
						|
    }
 | 
						|
  }
 | 
						|
 | 
						|
  fPImpl->fState->reading++;
 | 
						|
  CHECKSAFETY();
 | 
						|
  CHECKLIVENESS();
 | 
						|
  up(MUTEX);
 | 
						|
}
 | 
						|
 | 
						|
void RWLock::reset()
 | 
						|
{
 | 
						|
  fPImpl->fState->writerswaiting = 0;
 | 
						|
  fPImpl->fState->readerswaiting = 0;
 | 
						|
  fPImpl->fState->reading = 0;
 | 
						|
  fPImpl->fState->writing = 0;
 | 
						|
 | 
						|
  for (int i = 0; i < 3; i++)
 | 
						|
  {
 | 
						|
    while (fPImpl->fState->sems[i].try_wait())
 | 
						|
    {
 | 
						|
    }
 | 
						|
  }
 | 
						|
 | 
						|
  fPImpl->fState->sems[MUTEX].post();
 | 
						|
}
 | 
						|
 | 
						|
LockState RWLock::getLockState()
 | 
						|
{
 | 
						|
  bool gotIt;
 | 
						|
  LockState ret;
 | 
						|
 | 
						|
  gotIt = fPImpl->fState->sems[MUTEX].try_wait();
 | 
						|
  ret.reading = fPImpl->fState->reading;
 | 
						|
  ret.writing = fPImpl->fState->writing;
 | 
						|
  ret.readerswaiting = fPImpl->fState->readerswaiting;
 | 
						|
  ret.writerswaiting = fPImpl->fState->writerswaiting;
 | 
						|
  ret.mutexLocked = !gotIt;
 | 
						|
 | 
						|
  if (gotIt)
 | 
						|
    fPImpl->fState->sems[MUTEX].post();
 | 
						|
 | 
						|
  return ret;
 | 
						|
}
 | 
						|
 | 
						|
}  // namespace rwlock
 |