On Mon, Sep 22, 2008 at 1:05 PM, Anthony Williams <anthony.ajw@gmail.com> wrote:
"Felipe Magno de Almeida" <felipe.m.almeida@gmail.com> writes:
I would like to know if the storage created for boost::thread_specific_ptr in the tss specific code for win32 is free'd after the destruction of said boost::thread_specific_ptr, or if it stays until the end of the process.
Storage is allocated on a per-thread basis, and freed when the thread exits.
For example:
for(int i = very_big_number;i--;i > 0) boost::thread_specific_ptr<int> p(new int);
To my knowledge, the pointer returned by new in this case is freed. But does the int* that is created to store the pointer to new int is also freed, or this program will get only bigger and bigger?
As written this code is fine: it will reuse the same slot since p will have the same address each time through, and it uses the address as the key. It is undefined behaviour if other threads can still try and access a given thread_specific_ptr (including having data stored associated with it) after it has been destroyed.
Well, so for spirit it would indeed get only bigger. Since it will hardly reuse slots. I see the tss algorithm is linear as well.
If you create and destroy thread_specific_ptr instances all over the place then in general this will increase the list for each thread that accesses the tsp. It shouldn't be too hard to have the TSS entry be removed from the list when it is no longer needed. I'll try and get round to sorting it for Boost 1.37. If you raise a trac ticket I'll be more likely to remember.
Would this work? It seems to fix my problem: Index: boost/thread/tss.hpp =================================================================== --- boost/thread/tss.hpp (revisão 46411) +++ boost/thread/tss.hpp (cópia de trabalho) @@ -22,6 +22,7 @@ virtual void operator()(void* data)=0; }; + BOOST_THREAD_DECL void remove_tss_data(void const* key,boost::shared_ptr<tss_cleanup_function> func,void* tss_data,bool cleanup_existing); BOOST_THREAD_DECL void set_tss_data(void const* key,boost::shared_ptr<tss_cleanup_function> func,void* tss_data,bool cleanup_existing); BOOST_THREAD_DECL void* get_tss_data(void const* key); } @@ -74,6 +75,7 @@ ~thread_specific_ptr() { reset(); + detail::remove_tss_data(this,cleanup,0,true); } T* get() const Index: libs/thread/src/win32/thread.cpp =================================================================== --- libs/thread/src/win32/thread.cpp (revisão 46411) +++ libs/thread/src/win32/thread.cpp (cópia de trabalho) @@ -541,6 +541,40 @@ } return NULL; } + + void remove_tss_data(void const* key,boost::shared_ptr<tss_cleanup_function> func,void* tss_data,bool cleanup_existing) + { + tss_cleanup_implemented(); // if anyone uses TSS, we need the cleanup linked in + detail::thread_data_base* const current_thread_data(get_current_thread_data()); + if(current_thread_data) + { + detail::tss_data_node* current_node=current_thread_data->tss_data + , *previous_node = 0; + while(current_node) + { + if(current_node->key==key) + { + // found + if(previous_node) + { + current_node = current_node->next; + heap_delete<tss_data_node>(previous_node->next); + previous_node->next = current_node; + } + else + { + previous_node = current_node; + current_node = current_node->next; + heap_delete<tss_data_node>(previous_node); + current_thread_data->tss_data = current_node; + } + break; + } + previous_node = current_node; + current_node=current_node->next; + } + } + } void set_tss_data(void const* key,boost::shared_ptr<tss_cleanup_function> func,void* tss_data,bool cleanup_existing) {
Anthony -- Anthony Williams | Just Software Solutions Ltd Custom Software Development | http://www.justsoftwaresolutions.co.uk Registered in England, Company Number 5478976. Registered Office: 15 Carrallack Mews, St Just, Cornwall, TR19 7UL
Thanks, -- Felipe Magno de Almeida