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made latch-free unprotected_norehash_emplace_or_visit exception safe

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This commit is contained in:
joaquintides
2023-12-26 19:08:51 +01:00
parent f3f01e33f4
commit 71e9d35ab2
1 changed files with 41 additions and 10 deletions
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51
include/boost/unordered/detail/foa/concurrent_table.hpp
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@ -1579,6 +1579,38 @@ private:
};
#if defined(BOOST_UNORDERED_LATCH_FREE)
struct latch_free_reserve_slot
{
latch_free_reserve_slot(group_type* pg_,std::size_t pos_):pg{pg_},pos{pos_}
{
unsigned char expected=0;
succeeded_=reinterpret_cast<std::atomic<unsigned char>*>(pg)[pos].
compare_exchange_weak(expected,1);
}
~latch_free_reserve_slot()
{
if(succeeded_&&!commit_)pg->reset(pos);
}
bool succeeded()const{return succeeded_;}
void commit(){commit_=true;}
group_type *pg;
std::size_t pos;
bool succeeded_;
bool commit_=false;
};
struct assign_insert_counter_on_exit
{
~assign_insert_counter_on_exit(){counter=x;}
group_insert_counter_type &counter;
boost::uint32_t x;
};
template<typename GroupAccessMode,typename F,typename... Args>
BOOST_FORCEINLINE int
unprotected_norehash_emplace_or_visit(
@ -1592,7 +1624,6 @@ private:
startover:
boost::uint32_t counter=0;
while(BOOST_UNLIKELY((counter=insert_counter(pos0))%2==1)){}
if(unprotected_visit(
access_mode,k,pos0,hash,std::forward<F>(f)))return 0;
@ -1603,23 +1634,23 @@ private:
auto mask=pg->match_available();
if(BOOST_LIKELY(mask!=0)){
auto n=unchecked_countr_zero(mask);
unsigned char expected=0;
if(!reinterpret_cast<std::atomic<unsigned char>*>(pg)[n].
compare_exchange_weak(expected,1)){
latch_free_reserve_slot rslot{pg,n};
if(BOOST_UNLIKELY(!rslot.succeeded())){
/* slot wasn't empty */
goto startover;
}
auto p=this->arrays.elements()+pos*N+n;
this->construct_element(p,std::forward<Args>(args)...);
if(BOOST_UNLIKELY(
!insert_counter(pos0).compare_exchange_weak(counter,counter+1))){
/* other thread inserted from pos0, need to start over */
this->destroy_element(p);
pg->reset(n);
goto startover;
}
pg->set(n,hash);
insert_counter(pos0)=counter+2;
{
assign_insert_counter_on_exit a{insert_counter(pos0),counter+2};
auto p=this->arrays.elements()+pos*N+n;
this->construct_element(p,std::forward<Args>(args)...);
pg->set(n,hash);
}
rslot.commit();
auto& v=local_garbage_vector();
++v.size;
v.mcos-=!pg->is_not_overflowed(hash);