Pagefaulting in lock instruction

[Adam Lackorzynski]

On Wed May 04, 2005 at 11:08:26 +0100, Tiago Jorge wrote:
> hello...
> I'm having a strange page fault in my program.
> My server has an object called Consensus. This object its responsable in 
> the system to do consensus about something... an has an inner thread 
> that receives some parameters from outside.
> 
> its header file its the following
> 
> ##################################################
> 
> #ifndef CONSENSUS_H
> #define CONSENSUS_H
> 
> #include <fcntl.h>
> #include <stdlib.h>
> #include <netdb.h>
> #include <sys/types.h>
> #include <sys/socket.h>
> #include <netinet/in.h>
> #include <arpa/inet.h>
> 
> #include <l4/thread/thread.h>
> #include <l4/log/l4log.h>
> #include <l4/lock/lock.h>
> 
> #include "WOO_vector.h"
> #include "WOO_map.h"
> #include "WOO_string.h"
> 
> #include "FailureDetector.h"
> #include "Consensus_Packet.h"
> #include "WOO_TMO.h"
> #include "WOO_Groups.h"
> #include "WOO_common.h"
> #include "WOO_member.h"
> 
> #define CONSENSUS_PORTNUMBER 30987
> 
> struct estimate{
>   int eid;
>   vector<string> myEstimate;
> };
> 
> class Consensus{
> private:
>   int sock;
>   int trueFlag;
>   socklen_t addrLength;
>   struct sockaddr_in destinationAddr;
>   struct sockaddr_in myAddr;
>   struct sockaddr_in responseAddr;
>   estimate est;
>   phases current_phase;
>   bool mustRunConsensus;
>   //l4lock_t consensus_lock;
>   l4thread_t consTh;
>   int consensus_id;
>  
>   //params
>   int myEid;
>   vector<WOO_member>    *eids;
>   l4lock_t              *group_lock;
>   map<string, CWOO_TMO> *addr_TMO_running;
>   l4lock_t              *lock_TMO_running;
>   map<string, CWOO_TMO> *addr_TMO_decided;
>   l4lock_t              *lock_TMO_decided;
>   vector<CWOO_Groups>   *addr_WOO_groups_table;
>   l4lock_t              *lock_WOO_groups_table;
> public:
>   l4lock_t consensus_lock;
> 
> private:
>   void initialize_comm();
>   bool amICoordinator(vector<WOO_member> v);
>   int  coordinator(vector<WOO_member> v);
>   void copyGroup(vector<WOO_member> *toFill);
>   bool deadCoordinator(vector<WOO_member> v, FailureDetector *fd);
>   void cleanFailures(vector<WOO_member> *toClean, FailureDetector *fd);
>   void consensus_broadcast(vector<WOO_member> *toBroadcast, phases 
> phase, packet_type packet, int consensus_round);
>   vector<string> buildEstimate();
>   bool moreConsensus();
>   void decide();
> public:
>   Consensus();
>   void start(int eid,
>              vector<WOO_member>    *new_eids,
>              l4lock_t              *new_group_lock,
>              map<string, CWOO_TMO> *p_addr_TMO_running,
>              l4lock_t              *p_lock_TMO_running,
>              map<string, CWOO_TMO> *p_addr_TMO_decided,
>              l4lock_t              *p_lock_TMO_decided,
>              vector<CWOO_Groups>   *p_addr_WOO_groups_table,
>              l4lock_t              *p_lock_WOO_groups_table);
>   void consensus_impl();
>   void startConsensus();
>   void stopConsensus();
>   bool get_mustRunConsensus();
> };
> 
> void helper_consensus(void *args);
> 
> #endif // CONSENSUS_H
> 
> ##################################################
> 
> when someone wants to start the program we invoke start() that has this 
> code...
> 
> ##################################################
> 
> //passar aqui as TMOdecided e as TMOrunning e respectivos locks
> void
> Consensus::start (int new_eid,
>           vector < WOO_member > *new_eids,
>           l4lock_t * new_group_lock,
>           map < string, CWOO_TMO > *p_addr_TMO_running,
>           l4lock_t * p_lock_TMO_running,
>           map < string, CWOO_TMO > *p_addr_TMO_decided,
>           l4lock_t * p_lock_TMO_decided,
>           vector < CWOO_Groups > *p_addr_WOO_groups_table,
>           l4lock_t * p_lock_WOO_groups_table)
> {
>   myEid = new_eid;
>   eids = new_eids;
>   group_lock = new_group_lock;
>   consensus_id = 0;
>   trueFlag = 0x1;
> 
>   consensus_lock = L4LOCK_UNLOCKED;
> 
>   addr_TMO_running = p_addr_TMO_running;
>   lock_TMO_running = p_lock_TMO_running;
>   addr_TMO_decided = p_addr_TMO_decided;
>   lock_TMO_decided = p_lock_TMO_decided;
>   addr_WOO_groups_table = p_addr_WOO_groups_table;
>   lock_WOO_groups_table = p_lock_WOO_groups_table;
> 
>   /*consTh = l4thread_create (helper_consensus, this, 
> L4THREAD_CREATE_ASYNC);*/
> 
>   this->startConsensus();
>   this->consensus_impl();
>  
>   LOG ("estou dps do thread create\n");
> }
> 
> ##################################################
> 
> for testing porpuses the l4thread_create method its commented because 
> its page faulting also :(.
> Because it page-faulted when i've called the object's method that its 
> inside helper_consensus...
> 
> ##################################################
> 
> void
> helper_consensus (void *args)
> {
>   Consensus *cobj = static_cast<Consensus *>(args);
>   cobj->consensus_impl();
> }
> 
> ##################################################
> 
> i thought it was pagefaulting because of this method... but no... he 
> page-faults event when called normally... but the focus of the problem 
> it's not here yet.
> 
> when i call the startConsensus() method it page-faults in the 
> l4lock_lock(...) instruction...
> the method looks like this
> 
> ##################################################
> 
> void
> Consensus::startConsensus ()
> {
>   l4lock_lock(&consensus_lock); <---- it page faults here...
>   LOG("inside\n");
>   mustRunConsensus = true;
>   est.myEstimate = this->buildEstimate ();
>   LOG("out\n");
>   l4lock_unlock(&consensus_lock);
> }
> 
> ##################################################
> 
> here it is the dissassembled output...
> 
> ##################################################
> 
> <Consensus::startConsensus()>:
> /home/tiago/l4/pkg/WOO/server/src/Consensus_udp.cc:178
> 01db6a50        push   %ebp
> 01db6a51        mov    %esp,%ebp
> 01db6a53        push   %edi
> 01db6a54        push   %esi
> 01db6a55        push   %ebx
> 01db6a56        sub    $0xc37c,%esp
> 01db6a5c        mov    8(%ebp),%ebx
> /home/tiago/l4/include/l4/lock/lock.h:97
> 01db6a5f        lea    0xc3c8(%ebx),%eax
> 01db6a65        mov    %eax,0xffff3c84(%ebp) <<--- PAGE FAULT 
> HERE!!!!!!!!!!!!
> /home/tiago/l4/include/l4/lock/lock.h:98
> 01db6a6b        call   0x1dc0e80 <l4thread_myself>
> /home/tiago/l4/include/l4/lock/lock.h:101
> 01db6a70        mov    0xffff3c84(%ebp),%ecx
> /home/tiago/l4/include/l4/lock/lock.h:98
> 01db6a76        mov    %eax,0xffff3c80(%ebp)
> /home/tiago/l4/include/l4/lock/lock.h:101
> 01db6a7c        test   %ecx,%ecx
> 01db6a7e        je     0x1db6aa6
> 
> ##################################################
> 
> as of my inexperience with Fiasco debug issues... what might be causing 
> this?


Looking at the asm I wonder how the object is initialized and where does
it get its memory from?
And who's the pager of the object/thread?




Adam
-- 
Adam                 adam at os.inf.tu-dresden.de
  Lackorzynski         http://os.inf.tu-dresden.de/~adam/