以下是运行Helgrind的输出，它检测数据争用。它表明 内存位置0x5C8AD88是在没有受到保护的情况下共享的。
==7568== ----------------------------------------------------------------
==7568==
==7568== Possible data race during read of size 8 at 0x5C8AD88 by thread #3
==7568== Locks held: none
==7568== at 0x406616: std::_Rb_tree<long, std::pair<long const, demon::Edge*>, std::_Select1st<std::pair<long const, demon::Edge*> >, std::less<long>, std::allocator<std::pair<long const, demon::Edge*> > >::_S_right(std::_Rb_tree_node_base*) (stl_tree.h:535)
==7568== by 0x4102F1: std::_Rb_tree<long, std::pair<long const, demon::Edge*>, std::_Select1st<std::pair<long const, demon::Edge*> >, std::less<long>, std::allocator<std::pair<long const, demon::Edge*> > >::equal_range(long const&) (stl_tree.h:1174)
==7568== by 0x40FE1E: std::_Rb_tree<long, std::pair<long const, demon::Edge*>, std::_Select1st<std::pair<long const, demon::Edge*> >, std::less<long>, std::allocator<std::pair<long const, demon::Edge*> > >::erase(long const&) (stl_tree.h:1521)
==7568== by 0x40FA70: std::map<long, demon::Edge*, std::less<long>, std::allocator<std::pair<long const, demon::Edge*> > >::erase(long const&) (stl_map.h:654)
==7568== by 0x40F599: demon::Vertex::eliminate(demon::CGraph&) (Vertex.cpp:286)
==7568== by 0x404723: demon::CGraph::reverse_eliminate(int, demon::CGPart*) (CGraph.cpp:390)
==7568== by 0x404959: demon::CGraph::reverse_eliminate(void*) (CGraph.cpp:441)
==7568== by 0x40CC74: ThreadPool::execute_task(void*) (ThreadPool.cpp:156)
==7568== by 0x4C2ED9D: ??? (in /usr/lib64/valgrind/vgpreload_helgrind-amd64-linux.so)
==7568== by 0x4E3DE0E: start_thread (in /lib64/libpthread-2.17.so)
==7568== by 0x59547DC: clone (in /lib64/libc-2.17.so)
==7568==
==7568== This conflicts with a previous write of size 8 by thread #1
==7568== Locks held: none
==7568== at 0x50CB6B0: std::_Rb_tree_insert_and_rebalance(bool, std::_Rb_tree_node_base*, std::_Rb_tree_node_base*, std::_Rb_tree_node_base&) (in /usr/lib64/libstdc++.so.6.0.17)
==7568== by 0x410165: std::_Rb_tree<long, std::pair<long const, demon::Edge*>, std::_Select1st<std::pair<long const, demon::Edge*> >, std::less<long>, std::allocator<std::pair<long const, demon::Edge*> > >::_M_insert_(std::_Rb_tree_node_base const*, std::_Rb_tree_node_base const*, std::pair<long const, demon::Edge*> const&) (stl_tree.h:981)
==7568== by 0x40FD6D: std::_Rb_tree<long, std::pair<long const, demon::Edge*>, std::_Select1st<std::pair<long const, demon::Edge*> >, std::less<long>, std::allocator<std::pair<long const, demon::Edge*> > >::_M_insert_unique(std::pair<long const, demon::Edge*> const&) (stl_tree.h:1299)
==7568== by 0x40FA28: std::map<long, demon::Edge*, std::less<long>, std::allocator<std::pair<long const, demon::Edge*> > >::insert(std::pair<long const, demon::Edge*> const&) (stl_map.h:523)
==7568== by 0x40EFF4: demon::Vertex::add_in_edge(demon::Vertex*, double) (Vertex.cpp:213)
==7568== by 0x4049AA: demon::CGraph::add_edge(demon::Vertex*, demon::Vertex*, double) (CGraph.cpp:453)
==7568== by 0x408AB4: demon::CGBuilder::build_cg(demon::active const&, double, demon::active const&, double, demon::active const&, bool, bool) (CGBuilder.cpp:221)
==7568== by 0x40314D: demon::binary_op(demon::active const&, double, demon::active const&, double, demon::active const&, bool, bool) (API.cpp:55)
==7568==
==7568== Address 0x5C8AD88 is 24 bytes inside a block of size 48 alloc'd
==7568== at 0x4C2BD37: operator new(unsigned long) (in /usr/lib64/valgrind/vgpreload_helgrind-amd64-linux.so)
==7568== by 0x4108BE: __gnu_cxx::new_allocator<std::_Rb_tree_node<std::pair<long const, demon::Edge*> > >::allocate(unsigned long, void const*) (new_allocator.h:94)
==7568== by 0x410795: std::_Rb_tree<long, std::pair<long const, demon::Edge*>, std::_Select1st<std::pair<long const, demon::Edge*> >, std::less<long>, std::allocator<std::pair<long const, demon::Edge*> > >::_M_get_node() (stl_tree.h:369)
==7568== by 0x410516: std::_Rb_tree<long, std::pair<long const, demon::Edge*>, std::_Select1st<std::pair<long const, demon::Edge*> >, std::less<long>, std::allocator<std::pair<long const, demon::Edge*> > >::_M_create_node(std::pair<long const, demon::Edge*> const&) (stl_tree.h:379)
==7568== by 0x410146: std::_Rb_tree<long, std::pair<long const, demon::Edge*>, std::_Select1st<std::pair<long const, demon::Edge*> >, std::less<long>, std::allocator<std::pair<long const, demon::Edge*> > >::_M_insert_(std::_Rb_tree_node_base const*, std::_Rb_tree_node_base const*, std::pair<long const, demon::Edge*> const&) (stl_tree.h:979)
==7568== by 0x40FD6D: std::_Rb_tree<long, std::pair<long const, demon::Edge*>, std::_Select1st<std::pair<long const, demon::Edge*> >, std::less<long>, std::allocator<std::pair<long const, demon::Edge*> > >::_M_insert_unique(std::pair<long const, demon::Edge*> const&) (stl_tree.h:1299)
==7568== by 0x40FA28: std::map<long, demon::Edge*, std::less<long>, std::allocator<std::pair<long const, demon::Edge*> > >::insert(std::pair<long const, demon::Edge*> const&) (stl_map.h:523)
==7568== by 0x40EFF4: demon::Vertex::add_in_edge(demon::Vertex*, double) (Vertex.cpp:213)
==7568== by 0x4049AA: demon::CGraph::add_edge(demon::Vertex*, demon::Vertex*, double) (CGraph.cpp:453)
==7568== by 0x40890F: demon::CGBuilder::build_cg(demon::active const&, double, demon::active const&, bool, bool, bool) (CGBuilder.cpp:170)
==7568== by 0x4030D4: demon::unary_op(demon::active const&, double, demon::active const&, bool, bool, bool) (API.cpp:50)
==7568== by 0x402629: demon::operator*(double, demon::active const&) (Active.cpp:92)
==7568==
==7568== ----------------------------------------------------------------
此功能由线程＃1执行。
Edge * Vertex::add_in_edge( Vertex * src , double eval )
{
assert(src!=NULL);
Edge * in_et = new Edge( src, this, eval );
in_edges.insert( std::pair<idx_t,Edge*>( src->idx , in_et ) );
src->out_edges.insert( std::pair<idx_t,Edge*>( this->idx , in_et ) );
//pthread_mutex_lock(&ostream_lock);
//std::cout << "inside add_in_edge()" << std::endl;
//std::cout << "address of new inedge " << in_et << std::endl;
//std::cout << "address of this vertex " << this << std::endl;
//std::cout << "address of this vertex idx " << &(this->idx) << std::endl;
//std::cout << "address of src vertex " << src << std::endl;
//std::cout << "address of src vertex's outedge container " << &(src->out_edges) << std::endl;
//std::cout << "address of src vertex's inedge container " << &(src->in_edges) << std::endl;
//pthread_mutex_unlock(&ostream_lock);
return in_et;
}
此功能由线程＃3执行。
dim_t Vertex::eliminate( CGraph & cg )
{
dim_t nMults = 0;
std::map<idx_t,Edge*>::iterator inedge_it;
std::map<idx_t,Edge*>::iterator outedge_it;
dim_t m = in_edges.size();
dim_t n = out_edges.size();
//std::cout << "vertex " << idx << " is in block " << prt_idx << std::endl;
for( outedge_it=out_edges.begin() ; outedge_it!=out_edges.end() ; outedge_it++ )
outedge_it->second->tgt->in_edges.erase(this->idx);
for( inedge_it=in_edges.begin() ; inedge_it!=in_edges.end() ; inedge_it++ )
{
inedge_it->second->src->out_edges.erase(this->idx);
//pthread_mutex_lock(&ostream_lock);
//std::cout << "inside eliminate()" << std::endl;
//std::cout << "address of this edge " << inedge_it->second << std::endl;
//std::cout << "address of this vertex " << this << std::endl;
//std::cout << "address of this vertex idx " << &(this->idx) << std::endl;
//std::cout << "address of src vertex " << inedge_it->second->src << std::endl;
//std::cout << "address of src vertex's inedge container " << &(inedge_it->second->src->in_edges) << std::endl;
//std::cout << "address of src vertex's outedge container " << &(inedge_it->second->src->out_edges) << std::endl;
//pthread_mutex_unlock(&ostream_lock);
for( outedge_it=out_edges.begin() ; outedge_it!=out_edges.end() ; outedge_it++ )
{
double cij = (inedge_it->second->eval)*(outedge_it->second->eval);
nMults++;
Edge * direct_link = NULL;
std::map<idx_t,Edge*>::iterator direct_link_it;
direct_link_it = inedge_it->second->src->out_edges.find(outedge_it->second->tgt->idx);
if(direct_link_it!=inedge_it->second->src->out_edges.end())
{
direct_link = direct_link_it->second;
}
if(direct_link)
{
direct_link->eval += cij;
}else
{
outedge_it->second->tgt->add_in_edge( inedge_it->second->src , cij );
}
}
delete inedge_it->second;
}
for( outedge_it=out_edges.begin() ; outedge_it!=out_edges.end() ; outedge_it++ )
{
delete outedge_it->second;
}
in_edges.clear();
out_edges.clear();
return nMults;
}
以下是Vertex类的外观。它已经超越并且没有了 分别存储传出和传入边缘。
class Vertex
{
public :
//unsigned char properties;
bool live;
bool temporary;
bool local;
/**************************************
*the unique identifier for each vertex
**************************************/
idx_t idx;
/********************************************
*which block/partition the vertex belongs to
*********************************************/
idx_t prt_idx;
/*******************************************************
*which kind of vertex the vertex is : INDEP,INTMED,DEP
*******************************************************/
vertex_t kind;
/****************************************************************
*maps src vertex indinces to the corresponding incoming edges
*****************************************************************/
std::map<idx_t,Edge*> in_edges;
/*******************************************************************
*maps target vertex indinces to the corresponding outgoing edges
********************************************************************/
std::map<idx_t,Edge*> out_edges;
static pthread_mutex_t ostream_lock;
};//end of class
我正在尝试解释输出并找出位于0x5C8AD88的变量。
输出是否表明变量 * out_edges * 在inedge_it-＆gt; second-＆gt; src-＆gt; out_edges（来自函数elimination（））和src-＆gt; out_edges.insert（std :: pair（this-＆gt; idx，in_et））（来自add_in_edge）是罪魁祸首？
答案 0 :(得分：3)
答案在第三块输出中：
Address 0x5C8AD88 is 24 bytes inside a block of size 48 alloc'd
...
[...]::insert(std::pair<long const, demon::Edge*> const&)
demon::Vertex::add_in_edge(demon::Vertex*, double) (Vertex.cpp:213)
有问题的数据是add_in_edge()在insert()期间创建的。你真的可以在这里停下来。数据竞争是地图结构的某个地方。当然，您的代码不会显示对地图访问的任何锁定。您需要找出对in_edges和out_edges的所有访问的锁定方案。
在调查锁时，请考虑从低级pthread切换到std::thread。如果您不使用C ++ 11，请改用boost::thread。这些库中的互斥类更易于使用，并且不易出错。