In the x86 emu raised interrupt can be processed indefinitely over and over again under certain condition.

[Dmitry Klimenko]

Here is interrupt handler in the decode.c file:

static void x86emu_intr_handle(void)
{
 u8 intno;

 if (M.x86.intr & INTR_SYNCH) {
  intno = M.x86.intno;
  if (_X86EMU_intrTab[intno]) {
   (*_X86EMU_intrTab[intno])(intno);
  } else {
   push_word((u16)M.x86.R_FLG);
   CLEAR_FLAG(F_IF);
   CLEAR_FLAG(F_TF);
   push_word(M.x86.R_CS);
   M.x86.R_CS = mem_access_word(intno * 4 + 2);
   push_word(M.x86.R_IP);
   M.x86.R_IP = mem_access_word(intno * 4);
   M.x86.intr = 0;
  }
 }
}

If execution goes in the first branch,
(_X86EMU_intrTab[intno]) {
   (*_X86EMU_intrTab[intno])(intno);

M.x86.intr flag is not cleared in the interrupt preparation function in the table ( file thunk.c ):

static void x86emu_do_int(int num)
{
 u32 eflags;

 /* fprintf(stderr, "Calling INT 0x%X (%04X:%04X)\n", num,
   (read_b((num << 2) + 3) << 8) + read_b((num << 2) + 2),
   (read_b((num << 2) + 1) << 8) + read_b((num << 2)));

 fprintf(stderr, " EAX is %X\n", (int) X86_EAX);
 */

 eflags = X86_EFLAGS;
 eflags = eflags | X86_IF_MASK;
 pushw(eflags);
 pushw(X86_CS);
 pushw(X86_IP);
 X86_EFLAGS = X86_EFLAGS & ~(X86_VIF_MASK | X86_TF_MASK);
 X86_CS = (read_b((num << 2) + 3) << 8) + read_b((num << 2) + 2);
 X86_IP = (read_b((num << 2) + 1) << 8) + read_b((num << 2));

 /* fprintf(stderr, "Leaving interrupt call.\n"); */
}

thus, the handler is getting called at every iteration in the main emulation processor loop (decode.c ) since having been initially raised. Loop turns into indefinite one. Verified today.

void X86EMU_exec(void)
{
 u8 op1;

 M.x86.intr = 0;
 DB(x86emu_end_instr();)

    for (;;) {
DB( if (CHECK_IP_FETCH())
    x86emu_check_ip_access();)
  /* If debugging, save the IP and CS values. */
  SAVE_IP_CS(M.x86.R_CS, M.x86.R_IP);
  INC_DECODED_INST_LEN(1);
  if (M.x86.intr) {
   if (M.x86.intr & INTR_HALTED) { // ENTERED EVERY TIME after interrupt is raised - DK !!!
DB(
    X86EMU_trace_regs();)
    return;
            }
   if (((M.x86.intr & INTR_SYNCH) && (M.x86.intno == 0 || M.x86.intno == 2)) ||
    !ACCESS_FLAG(F_IF)) {
    x86emu_intr_handle();
   }
  }
  if ((M.x86.R_CS == 0) && (M.x86.R_IP == 0)) {
DB(
                                X86EMU_trace_regs();)
                                return;
  }

  op1 = (*sys_rdb)(((u32)M.x86.R_CS << 4) + (M.x86.R_IP++));
  // fprintf (stderr, "%s", M.x86.decoded_buf);
  // x86emu_dump_regs();
  (*x86emu_optab[op1])(op1);
    }
}

Package - Libx86_1.1, x86 Emulation part.
UBUNTU 10.04 LTS