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01bd50ad09d0a6768fb49be4d3ad6945d243ff27
mariadb-columnstore-engine/utils/rwlock/rwlock.cpp
david hill f6afc42dd0 the begginning
2016-01-06 14:08:59 -06:00

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/* Copyright (C) 2014 InfiniDB, Inc.
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; version 2 of
the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
MA 02110-1301, USA. */
/*****************************************************************************
* $Id$
*
****************************************************************************/
#include <unistd.h>
#include <iostream>
#include <stdexcept>
#include <string>
#include <sstream>
#include <iomanip>
#ifdef _MSC_VER
#include <unordered_map>
#else
#include <tr1/unordered_map>
#endif
#define NDEBUG
#include <cassert>
using namespace std;
#include <boost/thread/thread.hpp>
#include <boost/date_time/posix_time/posix_time.hpp>
#include <boost/interprocess/shared_memory_object.hpp>
#include <boost/interprocess/sync/named_semaphore.hpp>
#include <boost/version.hpp>
namespace bi=boost::interprocess;
#define RWLOCK_DLLEXPORT
#include "rwlock.h"
#undef RWLOCK_DLLEXPORT
using namespace boost::posix_time;
#include "shmkeys.h"
namespace
{
using namespace rwlock;
//This mutex needs to be fully instantiated by the runtime static object
// init mechanism or the lock in makeRWLockShmImpl() will fail
boost::mutex instanceMapMutex;
typedef std::tr1::unordered_map<int, RWLockShmImpl*> LockMap_t;
//Windows doesn't init static objects the same as Linux, so make this a ptr
LockMap_t* lockMapPtr=0;
}
namespace rwlock
{
#if defined(DEBUG) && !defined(_MSC_VER)
#define RWLOCK_DEBUG
#endif
#ifdef RWLOCK_DEBUG
#define PRINTSTATE() \
cerr << " reading = " << fPImpl->fState->reading << endl \
<< " writing = " << fPImpl->fState->writing << endl \
<< " readerswaiting = " << fPImpl->fState->readerswaiting << endl \
<< " writerswaiting = " << fPImpl->fState->writerswaiting << endl
#define CHECKSAFETY() \
do { if (!\
(\
(fPImpl->fState->reading == 0 && \
(fPImpl->fState->writing == 0 || fPImpl->fState->writing == 1)) || \
(fPImpl->fState->reading > 0 && fPImpl->fState->writing == 0) \
)) { \
cerr << __PRETTY_FUNCTION__ << ":" << __LINE__ << ": safety invariant violation" << endl; \
PRINTSTATE(); \
throw std::logic_error("RWLock: safety invariant violation"); \
} } while (0)
#define CHECKLIVENESS() \
do { if (!( \
(!(fPImpl->fState->readerswaiting > 0 || fPImpl->fState->writerswaiting > 0) || \
(fPImpl->fState->reading > 0 || fPImpl->fState->writing > 0)) || \
(!(fPImpl->fState->reading == 0 && fPImpl->fState->writing == 0) || \
(fPImpl->fState->readerswaiting == 0 && fPImpl->fState->writerswaiting == 0)) \
)) { \
cerr << __PRETTY_FUNCTION__ << ":" << __LINE__ << ": liveness invariant violation" << endl; \
PRINTSTATE(); \
throw std::logic_error("RWLock: liveness invariant violation"); \
} } while (0)
#else
#define PRINTSTATE() (void)0
#define CHECKSAFETY() (void)0
#define CHECKLIVENESS() (void)0
#endif
/*static*/
RWLockShmImpl* RWLockShmImpl::makeRWLockShmImpl(int key, bool* excl)
{
boost::mutex::scoped_lock lk(instanceMapMutex);
LockMap_t::iterator iter;
if (!lockMapPtr)
lockMapPtr = new LockMap_t();
iter = lockMapPtr->find(key);
if (iter == lockMapPtr->end())
{
RWLockShmImpl* ptr=0;
bool bExcl = excl ? *excl : false;
ptr = new RWLockShmImpl(key, bExcl);
lockMapPtr->insert(make_pair(key, ptr));
return ptr;
}
else if (excl)
{
*excl = false; // This isn't the first time for this lock.
}
return iter->second;
}
RWLockShmImpl::RWLockShmImpl(int key, bool excl)
{
string keyName = BRM::ShmKeys::keyToName(key);
fKeyString = keyName;
try
{
#if BOOST_VERSION < 104500
bi::shared_memory_object shm(bi::create_only, keyName.c_str(), bi::read_write);
#ifdef __linux__
{
string pname = "/dev/shm/" + keyName;
chmod(pname.c_str(), 0666);
}
#endif
#else
bi::permissions perms;
perms.set_unrestricted();
bi::shared_memory_object shm(bi::create_only, keyName.c_str(), bi::read_write, perms);
#endif
shm.truncate(sizeof(struct State));
fStateShm.swap(shm);
bi::mapped_region region(fStateShm, bi::read_write);
fRegion.swap(region);
fState = static_cast<State*>(fRegion.get_address());
fState->writerswaiting = 0;
fState->readerswaiting = 0;
fState->reading = 0;
if (excl)
fState->writing = 1;
else
fState->writing = 0;
new (&fState->sems[RWLock::MUTEX]) bi::interprocess_semaphore(1);
new (&fState->sems[RWLock::READERS]) bi::interprocess_semaphore(0);
new (&fState->sems[RWLock::WRITERS]) bi::interprocess_semaphore(0);
}
catch (bi::interprocess_exception&)
{
if (excl) {
//don't think we can get here anymore...
throw not_excl();
}
bi::shared_memory_object shm(bi::open_only, keyName.c_str(), bi::read_write);
fStateShm.swap(shm);
bi::mapped_region region(fStateShm, bi::read_write);
fRegion.swap(region);
fState = static_cast<State*>(fRegion.get_address());
}
catch (...)
{
runtime_error rex("RWLockShmImpl::RWLockShmImpl(): caught unknown exception");
cerr << rex.what() << endl;
throw rex;
}
}
RWLock::RWLock(int key, bool* excl)
{
fPImpl = RWLockShmImpl::makeRWLockShmImpl(key, excl);
}
RWLock::~RWLock()
{
}
void RWLock::down(int num, bool block)
{
again:
try {
if (block)
fPImpl->fState->sems[num].wait();
else {
bool gotIt = fPImpl->fState->sems[num].try_wait();
if (!gotIt)
throw wouldblock();
}
}
catch (bi::interprocess_exception& bipe) {
ostringstream os;
os << "RWLock::down(): caught boost ipe: " << bipe.what() << " key = " << fPImpl->keyString() <<
" error code = " << bipe.get_error_code();
if (bipe.get_error_code() == 1) // it passes through EINTR apparently
goto again;
runtime_error rex(os.str());
cerr << bipe.what() << endl;
throw rex;
} catch (std::exception& ex) {
cerr <<
#ifdef _MSC_VER
__FUNCTION__ <<
#else
__PRETTY_FUNCTION__ <<
#endif
":" << __LINE__ << ": caught an exception: " << ex.what() << endl;
throw;
} catch (...) {
cerr <<
#ifdef _MSC_VER
__FUNCTION__ <<
#else
__PRETTY_FUNCTION__ <<
#endif
":" << __LINE__ << ": caught an exception" << endl;
throw runtime_error("RWLock::down(): caught an exception");
}
}
bool RWLock::timed_down(int num, const ptime &delay)
{
bool gotTheLock = false;
// cout << "timed_down: current time = " << to_simple_string(microsec_clock::local_time()) <<
// " wake time = " << to_simple_string(delay) << endl;
again:
try {
// I don't think I've seen timed_wait() ever wait, need to do this 'manually'
//gotTheLock = fPImpl->fState->sems[num].timed_wait(delay);
do {
gotTheLock = fPImpl->fState->sems[num].try_wait();
if (!gotTheLock)
usleep(100000);
} while (!gotTheLock && microsec_clock::local_time() < delay);
}
catch (boost::thread_interrupted&) {
// no need to do anything here
}
catch (bi::interprocess_exception& bipe) {
ostringstream os;
os << "RWLock::timed_down(): caught boost ipe: " << bipe.what() << " key = " << fPImpl->keyString() <<
" error code = " << bipe.get_error_code();
if (bipe.get_error_code() == 1) // it passes through EINTR apparently
goto again;
runtime_error rex(os.str());
cerr << bipe.what() << endl;
throw rex;
}
catch (std::exception& ex) {
cerr <<
#ifdef _MSC_VER
__FUNCTION__ <<
#else
__PRETTY_FUNCTION__ <<
#endif
":" << __LINE__ << ": caught an exception: " << ex.what() << endl;
throw;
}
catch (...) {
cerr <<
#ifdef _MSC_VER
__FUNCTION__ <<
#else
__PRETTY_FUNCTION__ <<
#endif
":" << __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
// vim:ts=4 sw=4:
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