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// @file pagefault.h
/**
* Copyright (C) 2012 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
namespace mongo {
class Record;
class PageFaultException /*: public DBException*/ {
unsigned era;
const Record *r;
public:
PageFaultException(const PageFaultException& rhs) : era(rhs.era), r(rhs.r) { }
explicit PageFaultException(const Record*);
void touch();
};
class PageFaultRetryableSection : boost::noncopyable {
unsigned _laps;
public:
unsigned laps() const { return _laps; }
void didLap() { _laps++; }
PageFaultRetryableSection();
~PageFaultRetryableSection();
};
/**
* this turns off page faults in a scope
* there are just certain arease where its dangerous
* this might mean the code is dangerous anyway....
*/
class NoPageFaultsAllowed : boost::noncopyable {
public:
NoPageFaultsAllowed();
~NoPageFaultsAllowed();
private:
PageFaultRetryableSection* _saved;
};
#if 0
inline void how_to_use_example() {
// ...
{
PageFaultRetryableSection s;
while( 1 ) {
try {
writelock lk; // or readlock
// do work
break;
}
catch( PageFaultException& e ) {
e.touch();
}
}
}
// ...
}
#endif
}
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