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Problems coding a scheduler

/*
 * Hello, 
 * We are trying to make an operating system and we are using 
 * the Oskit tool. We are just starting and we have some problems related
 * to the IDT table.
 * We are trying to code an scheduler using the timer to interrupt
 * processes as you can see in the code below. It does not work
 * at all. 
 * The timer interrupt seems to occur just once and no more. The
 * first task switch to the scheduler happens but after that the
 * main function is not interrupted again. We think that the problem
 * is related to how the PIC has been programmed and we believe that it should
 * be programmed in the AUTO_EOI mode but OSKIT initialization seems
 * to program it in other mode. 
 * We think that the IDT and the TSS have been filled correctly.
 * What have we done wrong??
 * Thank you.

 *                                    Jose Fresnadillo 
 *                                    La Laguna University
 *                                    La Laguna, Tenerife. Spain. */


#include <stdio.h>
#include <oskit/machine/base_cpu.h>
#include <oskit/x86/pmode.h>
#include <oskit/x86/base_gdt.h>
#include <oskit/machine/base_vm.h>
#include <oskit/x86/tss.h>
#include <oskit/x86/base_tss.h>
#include <oskit/dev/dev.h>
#include <oskit/x86/proc_reg.h>
#include <oskit/x86/base_idt.h>
#include <oskit/debug.h>
#include <oskit/x86/pio.h>
#include <oskit/x86/pc/pit.h>
#include <oskit/x86/pc/base_irq.h>
#include <oskit/x86/base_trap.h>


#define USER_TSS1 0x58


CODE32

struct x86_tss user_base_tss1;
long dataseg[100];

/*
 * SCHEDULER.-
 * 
 */ 
void scheduler(void){
   
   printf("Scheduling...\n");
   asm("iret");
}

/* 
 * MAIN PROGRAM.-
 * 
 */
void main(void) {
   
   /* Make sure we're not already in protected mode.  */
   if (i16_get_msw() & CR0_PE)
	 printf("The processor is in protected mode environment.\n");
   
   base_gdt_init();
   base_gdt_load();
   base_tss_init();
   base_tss_load();
   
   fill_descriptor(&base_gdt[USER_TSS1 / 8],
				   &user_base_tss1, sizeof(user_base_tss1) - 1,
				   ACC_PL_K | ACC_TSS | ACC_P, 0);
   
   base_tss.eflags = base_tss.eflags | 0x202;
   
   user_base_tss1.eip = (long)&scheduler;
   user_base_tss1.cs  = KERNEL_CS;
   user_base_tss1.es  = KERNEL_DS;
   user_base_tss1.ds  = KERNEL_DS;
   user_base_tss1.ss  = KERNEL_DS;
   user_base_tss1.fs  = KERNEL_DS;
   user_base_tss1.gs  = KERNEL_DS;
   user_base_tss1.ss0 = KERNEL_DS;
   user_base_tss1.ss1 = KERNEL_DS;
   user_base_tss1.ss2 = KERNEL_DS;
   user_base_tss1.esp = sizeof(dataseg) * 100 + (long)dataseg;   
   user_base_tss1.esp0 = sizeof(dataseg) * 100 + (long)dataseg;
   user_base_tss1.esp1 = sizeof(dataseg) * 100 + (long)dataseg;      
   user_base_tss1.esp2 = sizeof(dataseg) * 100 + (long)dataseg;   
   user_base_tss1.io_bit_map_offset = sizeof(user_base_tss1);
   user_base_tss1.ldt = 0;
   user_base_tss1.eflags = 0x202;
   base_gdt[USER_TSS1 / 8].access &= ~ACC_TSS_BUSY;


   osenv_intr_disable();
   
   fill_gate(&base_idt[irq_master_base + 0], 0, USER_TSS1, 
			 ACC_TASK_GATE | ACC_PL_K, 0);
   pit_init(100);      
   osenv_irq_enable(0);

   osenv_intr_enable();   
   
   while (1)
	 ;
	 
   printf("Just in case...\n");
   
   return;
}
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