Possible race (FiascoOC) signalling?

Daniel Waddington d.waddington at ...60...
Fri Jul 29 02:37:45 CEST 2011


Hi,
I'm having problem with some intermittent error reported as follows:

[init -> test-pager-2] Test::Pager::Pager(): Pager constructed OK.
page fault (READ pf_addr=1004000 pf_ip=1011748 from 44a000)
page fault (READ pf_addr=1006000 pf_ip=1011748 from 44a000)
page fault (READ pf_addr=1008000 pf_ip=1011748 from 44a000)
[init -> test-pager-2] Test-pager-2 example. ;-))
[init -> test-pager-2] Test::SharedMemory::SharedMemory(): About to 
start the pager.

KERNEL: Warning: nothing mapped: (Obj_space) from [0xfcdcedec/a3]: 
00000407 size: 00000001 to [0xfcdcedec/a3]

KERNEL: Warning: nothing mapped: (Obj_space) from [0xfcdcedec/a3]: 
0000040b size: 00000001 to [0xfcdcef4c/b]

KERNEL: Warning: nothing mapped: (Obj_space) from [0xfcdcef4c/b]: 
00000206 size: 00000001 to [0xfcdcef4c/b]

KERNEL: Warning: nothing mapped: (Obj_space) from [0xfcdcedec/a3]: 
0000040b size: 00000001 to [0xfcdcef4c/b]

KERNEL: Warning: nothing mapped: (Obj_space) from [0xfcdcef4c/b]: 
00000206 size: 00000001 to [0xfcdcef4c/b]
page fault (READ pf_addr=4db30 pf_ip=4db30 from 44a000)
page fault (READ pf_addr=4a310 pf_ip=4a310 from 44a000)
page fault (READ pf_addr=49ce0 pf_ip=49ce0 from 44a000)
page fault (READ pf_addr=6b004 pf_ip=4ac5b from 44a000)
page fault (READ pf_addr=6c008 pf_ip=4ac5b from 44a000)
page fault (READ pf_addr=6d000 pf_ip=4a958 from 44a000)
page fault (READ pf_addr=6e004 pf_ip=4ac5b from 44a000)
page fault (READ pf_addr=6f00c pf_ip=4ac5b from 44a000)
page fault (WRITE pf_addr=231c pf_ip=4c111 from 44a000)
page fault (READ pf_addr=47ae0 pf_ip=47ae0 from 44a000)
page fault (READ pf_addr=48134 pf_ip=48135 from 44a000)
page fault (READ pf_addr=8e034 pf_ip=4b17e from 44a000)
page fault (READ pf_addr=4eb70 pf_ip=4eb70 from 44a000)
page fault (READ pf_addr=44770 pf_ip=44770 from 44a000)
page fault (READ pf_addr=46030 pf_ip=46030 from 44a000)
page fault (READ pf_addr=456d0 pf_ip=456d0 from 44a000)
[init -> test-pager-2] C++ runtime: Genode::Rm_session::Invalid_thread
[init -> test-pager-2] void* abort(): abort called

In the following code it seems to occur as a result of the Signal / 
_receiver calls.

Any ideas??

#include <base/printf.h>
#include <base/sleep.h>
#include <base/rpc_server.h>
#include <cap_session/connection.h>
#include <dataspace/client.h>
#include <rom_session/connection.h>
#include <rm_session/connection.h>
#include <ram_session/connection.h>
#include <foc_cpu_session/foc_cpu_session.h>
#include <foc_cpu_session/client.h>

#include <root/component.h>
#include <util/avl_string.h>
#include <util/misc_math.h>
#include <assert.h>
#include <stdlib.h>

#include <omnios/thread.h>
#include <omnios/sleep.h>

#define PAGE_SIZE 4096
#define SHARED_MEMORY_SIZE (1*PAGE_SIZE)
using namespace Genode;

namespace Test
{

   /**
    * Example pager class
    *
    * @return
    */
   class Pager : public OmniOS::Thread
   {
   private:

     Signal_receiver _receiver;

   public:

     // ctor
     Pager() {
       PDBG("Pager constructed OK.");
     }

     Signal_receiver *signal_receiver() { return &_receiver; }

     void entry();
   };

   /**
    * Example backing store class - this one uses physical memory
    *
    */
   class Physical_backing_store : public Signal_context
   {
   private:
     Rm_connection _rm;
     Genode::size_t _size;
     Dataspace_capability _ds;
     Dataspace_client _ds_client;
     unsigned long _iter;

   public:
     // ctor
     Physical_backing_store(Genode::size_t size):
       _rm(0,size),
       _ds(env()->ram_session()->alloc(SHARED_MEMORY_SIZE)),
       _ds_client(_ds),
       _iter(0)
     {
       _size = size;
       assert(_size > 0);
     }

     virtual ~Physical_backing_store() {
     }

     /**
      * Page fault handler.
      *
      */
     void handle_fault()
     {
       Rm_session::State state = _rm.state();

       if(state.type != Rm_session::READY) {
         if(__sync_fetch_and_add(&_iter,1) > 0) {
           PDBG("Entered PF handler again!!!\n");
           return;
         }
         else PDBG("Entered PF handler for 1st time!\n");
       }


       printf("Test::Physical_backing_store:: rm session state is %s, 
pf_addr=0x%lx\n",
              state.type == Rm_session::READ_FAULT  ? "READ_FAULT"  :
              state.type == Rm_session::WRITE_FAULT ? "WRITE_FAULT" :
              state.type == Rm_session::EXEC_FAULT  ? "EXEC_FAULT"  : 
"READY",
              state.addr);

       if (state.type == Rm_session::READY)
         return;

       try {

         try {

           /* print out the physical address */
           {
             Genode::addr_t addr = _ds_client.phys_addr();
             printf("Physical addr of dataspace:0x%lX\n",addr);
           }


           /* write something in for testing */
           char * addr = (char*) env()->rm_session()->attach(_ds);

           assert(addr);
           addr[0] = 1; addr[1] = 2;  addr[2] = 3;

           env()->rm_session()->detach((void*)addr);

         }
         catch(...) { PERR("Actual page allocation failed.\n"); }


         _rm.attach_at(_ds, state.addr & ~(PAGE_SIZE - 1));

         PDBG("attached data space OK!\n");
       }
       catch (Genode::Rm_session::Region_conflict) {
         PERR("Region conflict - this should not happen\n");
       }
       catch (Genode::Rm_session::Out_of_metadata) {
         PERR("Out of meta data!\n");
       }
       catch(...) {
         PERR("Something else caused attach to fail in fault handler.\n");
       }

       return;
     }

     Rm_connection *rm() { return &_rm; }
     Dataspace_capability ds() { return _rm.dataspace(); }

     void connect_pager(Pager& _pager) {
       /* connect pager signal receiver to the fault handler */
       _rm.fault_handler(_pager.signal_receiver()->manage(this));
     }

   };


   /**
    * Entry point for pager thread.
    *
    */
   void Pager::entry()
   {
     while (true) {
       try {
         //  THIS code BREAKS THINGS
         Signal signal = _receiver.wait_for_signal();

         for (int i = 0; i < signal.num(); i++) {
            static_cast<Physical_backing_store 
*>(signal.context())->handle_fault();
         }
       } catch (...) {
         PDBG("unexpected error while waiting for signal");
       }
     }
   }

   class SharedMemory
   {
   private:
     void * _vaddr;

     Genode::Cancelable_lock _vaddr_lock;
     Test::Physical_backing_store _bs;

     /* create pager object */
     static Test::Pager _pager;


   public:


     SharedMemory(): _vaddr(NULL),_bs(SHARED_MEMORY_SIZE) {

       PDBG("About to start the pager.");
       /* lets start the pager thread */
       _pager.start();

       /* allocate some backing store */
       try {

         /* connect pager to fault handler */
         _bs.connect_pager(_pager);

         /* attach to dataspace */
         assert(!_vaddr);

         addr_t target_va = 0xfff000; /* look, we can use a specific VA 
address */

         PDBG("About to attach to vaddr (0x%p)\n",_vaddr);
         _vaddr = 
env()->rm_session()->attach(_bs.ds(),SHARED_MEMORY_SIZE,0,true,target_va);
         PDBG("Attached dataspace to vaddr (0x%p)\n",_vaddr);
         assert(_vaddr);
       }
       catch(...) {
         PERR("Something failed in SharedMemory ctor.\n");
         enter_kdebug("Unexpected condition.");
       }



     }

     void r_access(unsigned int tid) {
       assert(_vaddr);

       /* trigger read fault */
       char* c = (char*) _vaddr;
       printf("Read (va=%p) [%d %d %d] (tid=%u)\n",c,c[0],c[1],c[2],tid);
     }

     void w_access() {
       assert(_vaddr);
       /* trigger write fault */
       char* c = (char*) _vaddr;
       c[0]=2;
       c[1]=3;
       c[2]=4;
     }

   };


   /* static initializers */
   Test::Pager Test::SharedMemory::_pager;

}


int main()
{
   Genode::printf("Test-pager-2 example. ;-))\n");

   Test::SharedMemory shmem;
   Genode::printf("shmem created ok.\n");

   Genode::sleep_forever();
   return 0;
}


-- 

*Daniel G. Waddington Ph.D. C.Sci. **| **Samsung Information Systems 
America (SISA)*

Principal Engineer/Research Manager, Systems Research Group, Computer 
Science Lab

t: 408-544-5675 f: 408-544-5540 c: 408-890-0479

d.waddington at ...60... <mailto:d.waddington at ...60...>

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