/* Switch execution transparently to thread TO. The thread FROM,
which must be the current thread, will be halted. */
void
switch_thread (l4_thread_id_t from, l4_thread_id_t to)
{
void *current_stack;
/* FIXME: Figure out how much we need. Probably only one return
address. */
char small_sub_stack[16];
unsigned int i;
/* FIXME: FROM is an argument to force gcc to evaluate it before the
thread switch. Maybe this can be done better, but it's
magical, so be careful. */
/* Save the machine context. */
__asm__ __volatile__ ("pusha");
__asm__ __volatile__ ("pushf");
/* Start the TO thread. It will be eventually become a clone of our
thread. */
current_stack = __thread_stack_pointer ();
l4_start_sp_ip (to, (l4_word_t) current_stack,
(l4_word_t) &&thread_switch_entry);
/* We need a bit of extra space on the stack for
l4_thread_switch. */
__thread_set_stack_pointer (small_sub_stack + sizeof (small_sub_stack));
/* We can't use while(1), because then gcc will become clever and
optimize away everything after thread_switch_entry. */
for (i = 1; i; i++)
l4_thread_switch (to);
thread_switch_entry:
/* Restore the machine context. */
__asm__ __volatile__ ("popf");
__asm__ __volatile__ ("popa");
/* The thread TO continues here. */
l4_stop (from);
}
int
cthread_sp(void)
{
return (int) __thread_stack_pointer ();
}
