static int allocate_transition_tls(int id)
{
/* Libc function to initialize TLS-based locale info for ctype functions. */
extern void __ctype_init(void);
/* We want to free and then reallocate the tls rather than simply
* reinitializing it because its size may have changed. TODO: not sure if
* this is right. 0-ing is one thing, but freeing and reallocating can be
* expensive, esp if syscalls are involved. Check out glibc's
* allocatestack.c for what might work. */
free_transition_tls(id);
void *tcb = allocate_tls();
if (!tcb) {
errno = ENOMEM;
return -1;
}
/* Setup some intitial TLS data for the newly allocated transition tls. */
void *temp_tcb = get_tls_desc();
set_tls_desc(tcb);
begin_safe_access_tls_vars();
__vcoreid = id;
__vcore_context = TRUE;
__ctype_init();
end_safe_access_tls_vars();
set_tls_desc(temp_tcb);
/* Install the new tls into the vcpd. */
set_vcpd_tls_desc(id, tcb);
return 0;
}
/* Helper, makes VC ctx tracks uthread as its current_uthread in its TLS.
*
* Whether or not uthreads have TLS, thread0 has TLS, given to it by glibc.
* This TLS will get set whenever we use thread0, regardless of whether or not
* we use TLS for uthreads in general. glibc cares about this TLS and will use
* it at exit. We can't simply use that TLS for VC0 either, since we don't know
* where thread0 will be running when the program ends. */
static void uthread_track_thread0(struct uthread *uthread)
{
set_tls_desc(get_vcpd_tls_desc(0));
begin_safe_access_tls_vars();
/* We might have a basic uthread already installed (from a prior call), so
* free it before installing the new one. */
if (current_uthread)
free(current_uthread);
current_uthread = uthread;
/* We may not be an MCP at this point (and thus not really working with
* vcores), but there is still the notion of something vcore_context-like
* even when running as an SCP (i.e. its more of a scheduler_context than a
* vcore_context). Threfore we need to set __vcore_context to TRUE here to
* represent this (otherwise we will hit some asserts of not being in
* vcore_context when running in scheduler_context for the SCP. */
__vcore_context = TRUE;
end_safe_access_tls_vars();
set_tls_desc(uthread->tls_desc);
}
