void *lat_ctx2_thread0(void *ptr)
{
int tmp_iterations;
Pr_Time overhead;
Pr_Time time_spent, tmp, total_time;
/* Obtain the timing overhead */
printf("Task0: Hello, let's init_timing()\n");
init_timing();
/* Calculate the number of executions of do_overhead1() that can
* be done in 1 second */
tmp_iterations = generate_iterations (&do_overhead1, 1);
printf("%d complete iterations in 1 second\n", tmp_iterations);
/* Now obtains the token passing overhead */
tmp_iterations >>= 1;
overhead = 0.0;
do_overhead2(tmp_iterations, &overhead);
/* After obtaining all the overheads, it launches the context swith latency
* measuring process */
do_context_switch(NUM_ITERATIONS, &time_spent);
/* Now, it calculates the context swith latency time */
printf("Time spent: %d\n", (uint32)time_spent.Micros());
tmp = (float)(overhead.Secns() * (float)(NUM_ITERATIONS * NUM_TASKS));
printf("Total overhead: %d\n", (uint32)tmp.Micros());
time_spent -= tmp;
total_time = (float)(time_spent.Secns() / (NUM_ITERATIONS * NUM_TASKS));
printf("Latency of context switch: %d usecs\n", (uint32)total_time.Micros());
Testlat_ctx2.End();
return NULL;
}
void context_switch(struct kthread * new_thread)
{
/*
* For switching to the new task
* Math state must be saved,
*/
math_state_save((struct fpu_state *)¤t_thread->kt_fps);
math_state_restore(&new_thread->kt_fps);
// Save cr0
current_thread->kt_cr0 = get_cr0();
// Change current process inf necessary
current_process = new_thread->kt_process;
new_thread->kt_schedinf.sc_state = THREAD_STATE_RUNNING;
gdt_table[new_thread->kt_tssdesc >> 3].b &= 0xfffffdff;
current_thread = new_thread;
do_context_switch(new_thread->kt_tssdesc, new_thread->kt_cr0, new_thread->kt_tss->cr3);
// process any pending timeout events
return;
}
