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Make transaction thread-safe

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Reviewers: dgleich

Reviewed By: dgleich

Subscribers: pullbot

Differential Revision: https://phabricator.memgraph.io/D1223
This commit is contained in:
florijan 2018-02-06 15:53:12 +01:00
parent 46b8a91a2f
commit 16853e5b8a
1 changed files with 17 additions and 1 deletions
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18
src/transactions/lock_store.hpp
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@ -1,10 +1,13 @@
#pragma once
#include <memory>
#include <mutex>
#include <vector>
#include "glog/logging.h"
#include "storage/locking/lock_status.hpp"
#include "storage/locking/record_lock.hpp"
#include "threading/sync/spinlock.hpp"
#include "transactions/type.hpp"
namespace tx {
@ -55,13 +58,26 @@ class LockStore {
public:
void Take(RecordLock *lock, const tx::Transaction &tx, tx::Engine &engine) {
locks_.emplace_back(LockHolder(lock, tx, engine));
// Creating a lock holder locks the version list to the given transaction.
// Note that it's an op that can take a long time (if there are multiple
// transactions trying to lock.
LockHolder holder{lock, tx, engine};
// This guard prevents the same transaction from concurrent modificaton of
// locks_. This can only happen in distributed memgraph, when there are
// multiple edits coming to the same worker in the same transaction at the
// same time. IMPORTANT: This guard must come after LockHolder construction,
// as that potentially takes a long time and this guard only needs to
// protect locks_ update.
std::lock_guard<SpinLock> guard{locks_lock_};
locks_.emplace_back(std::move(holder));
if (!locks_.back().active()) {
locks_.pop_back();
}
}
private:
SpinLock locks_lock_;
std::vector<LockHolder> locks_;
};
} // namespace tx