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Remove support for recursive-by-thread RWLocks because it makes no sense

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This commit is contained in:
Alexey Milovidov 2019-09-02 03:59:27 +03:00
parent 6cf5327269
commit 32adf456d8
2 changed files with 7 additions and 20 deletions
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22
dbms/src/Common/RWLock.cpp
View File

@ -37,7 +37,6 @@ class RWLockImpl::LockHolderImpl
RWLock parent;
GroupsContainer::iterator it_group;
ClientsContainer::iterator it_client;
ThreadToHolder::key_type thread_id;
QueryIdToHolder::key_type query_id;
CurrentMetrics::Increment active_client_increment;
@ -74,17 +73,12 @@ RWLockImpl::LockHolder RWLockImpl::getLock(RWLockImpl::Type type, const String &
/// Check if the same query is acquiring previously acquired lock
LockHolder existing_holder_ptr;
auto this_thread_id = std::this_thread::get_id();
auto it_thread = thread_to_holder.find(this_thread_id);
auto it_query = query_id_to_holder.end();
if (query_id != RWLockImpl::NO_QUERY)
it_query = query_id_to_holder.find(query_id);
if (it_thread != thread_to_holder.end())
existing_holder_ptr = it_thread->second.lock();
else if (it_query != query_id_to_holder.end())
existing_holder_ptr = it_query->second.lock();
{
auto it_query = query_id_to_holder.find(query_id);
if (it_query != query_id_to_holder.end())
existing_holder_ptr = it_query->second.lock();
}
if (existing_holder_ptr)
{
@ -125,10 +119,7 @@ RWLockImpl::LockHolder RWLockImpl::getLock(RWLockImpl::Type type, const String &
/// Wait a notification until we will be the only in the group.
it_group->cv.wait(lock, [&] () { return it_group == queue.begin(); });
/// Insert myself (weak_ptr to the holder) to threads set to implement recursive lock
thread_to_holder.emplace(this_thread_id, res);
res->thread_id = this_thread_id;
/// Insert myself (weak_ptr to the holder) to queries set to implement recursive lock
if (query_id != RWLockImpl::NO_QUERY)
query_id_to_holder.emplace(query_id, res);
res->query_id = query_id;
@ -143,7 +134,6 @@ RWLockImpl::LockHolderImpl::~LockHolderImpl()
std::unique_lock lock(parent->mutex);
/// Remove weak_ptrs to the holder, since there are no owners of the current lock
parent->thread_to_holder.erase(thread_id);
parent->query_id_to_holder.erase(query_id);
/// Removes myself from client list of our group

5
dbms/src/Common/RWLock.h
View File

@ -6,7 +6,6 @@
#include <vector>
#include <mutex>
#include <condition_variable>
#include <thread>
#include <map>
#include <string>
@ -19,7 +18,7 @@ using RWLock = std::shared_ptr<RWLockImpl>;
/// Implements shared lock with FIFO service
/// Can be acquired recursively (several calls for the same query or the same OS thread) in Read mode
/// Can be acquired recursively (several calls for the same query) in Read mode
///
/// NOTE: it is important to allow acquiring the same lock in Read mode without waiting if it is already
/// acquired by another thread of the same query. Otherwise the following deadlock is possible:
@ -55,7 +54,6 @@ private:
struct Group;
using GroupsContainer = std::list<Group>;
using ClientsContainer = std::list<Type>;
using ThreadToHolder = std::map<std::thread::id, std::weak_ptr<LockHolderImpl>>;
using QueryIdToHolder = std::map<String, std::weak_ptr<LockHolderImpl>>;
/// Group of clients that should be executed concurrently
@ -73,7 +71,6 @@ private:
mutable std::mutex mutex;
GroupsContainer queue;
ThreadToHolder thread_to_holder;
QueryIdToHolder query_id_to_holder;
};