Hi Kobi, I am using ACE_Mutex. Let me check ACE Guards (I know there is ACE_Guard class), Is that what you mean? Thanks Priyank ________________________________ From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Kobi Cohen-Arazi Sent: Thursday, May 11, 2006 11:09 AM To: boost-users@lists.boost.org Subject: Re: [Boost-users] [multi_index] Core dump in multi-index library !! Procedure * Procedure_Pool::find_by_id(int _id) { LD_TRACE("Procedure_Pool::find_by_id"); mutex_.acquire(); Procedure_By_Id::iterator it = procedure_by_id_.find(_id); if (it != procedure_by_id_.end()) { ACE_DEBUG((LM_DEBUG, "%N:%l Found procedure for id: %d \n", _id)); mutex_.release(); return *it; } ACE_DEBUG((LM_DEBUG, "%N:%l Not able to found procedure for id: %d \n", _id)); mutex_.release(); // return null return 0; } BTW, As a side note, I highly recommend you to use ACE Guards (RAII...) for the mutex thing. Kobi