Thanks Zwon,

I had not created any interpreter (perl_alloc) in the thread earlier. I now tried this and it still fails/seg faults inside call_sv(). I'm still trying to understand if I need perl_parse and if I should do a perl_clone rather than perl_alloc. Also, unclear if there is any "locking"/mutual exclusion between the two interpreters required before invoking call_sv

Are there any other forums with more experience in this that I should post at? 

void mythread_fn(void)
{

         static PerlInterpreter *my_perl=NULL;

         my_perl = perl_alloc();
         PERL_SET_CONTEXT(my_perl);
         perl_construct(my_perl);
         perl_run(my_perl);

         while (1)
         {

             /* monitor for events */
             if (event == xyz)
                 callback_handler(event);
         }

        perl_destruct(my_perl);
        perl_free(my_perl);
}

void callback_handler(int event)
{
      dTHX;
      dSP;

      ENTER;
      SAVETMPS;

      SV * sv = disc_callback;  /* saved earlier in an API call */
      if (sv == (SV*)NULL)
         croak("Internal error...\n");

      PUSHMARK(SP);
      XPUSHs(sv_2mortal(newSViv(event)));
      PUTBACK;

      /* Call the Perl sub */
      call_sv(sv, G_DISCARD);  /* crashes as shown below in gdb */

      FREETMPS;
      LEAVE;
}

Part of gdb stacktrace.

#0  Perl_pp_entersub (my_perl=0x6587b0) at pp_hot.c:2945
#1  0x00000000004224f3 in S_call_body (my_perl=0x6587b0, myop=0x65a6e0
+,
    is_eval=1 '\001') at perl.c:2728
#2  0x00000000004223c4 in Perl_call_sv (my_perl=0x6587b0, sv=0x635420,
+ flags=2)
    at perl.c:2607

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In reply to Re^2: my_perl is NULL when embed perl in C ; "dSP" segmentation faults by perlmonk1729
in thread Working with multiple interpreters (my_perl is NULL when embed perl in C ; "dSP" segmentation faults) by perlmonk1729

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