Function thread_exit

freebsd/kern/kern_thread.c:848–955

* Discard the current thread and exit from its context. * Always called with scheduler locked. * * Because we can't free a thread while we're operating under its context, * push the current thread into our CPU's deadthread holder. This means * we needn't worry about someone else grabbing our context before we * do a cpu_throw(). */

 * do a cpu_throw().
 */
void
thread_exit(void)
{
	uint64_t runtime, new_switchtime;
	struct thread *td;
	struct thread *td2;
	struct proc *p;
	int wakeup_swapper;

	td = curthread;
	p = td->td_proc;

	PROC_SLOCK_ASSERT(p, MA_OWNED);
	mtx_assert(&Giant, MA_NOTOWNED);

	PROC_LOCK_ASSERT(p, MA_OWNED);
	KASSERT(p != NULL, ("thread exiting without a process"));
	CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
	    (long)p->p_pid, td->td_name);
	SDT_PROBE0(proc, , , lwp__exit);
	KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
	MPASS(td->td_realucred == td->td_ucred);

	/*
	 * drop FPU & debug register state storage, or any other
	 * architecture specific resources that
	 * would not be on a new untouched process.
	 */
	cpu_thread_exit(td);

	/*
	 * The last thread is left attached to the process
	 * So that the whole bundle gets recycled. Skip
	 * all this stuff if we never had threads.
	 * EXIT clears all sign of other threads when
	 * it goes to single threading, so the last thread always
	 * takes the short path.
	 */
	if (p->p_flag & P_HADTHREADS) {
		if (p->p_numthreads > 1) {
			atomic_add_int(&td->td_proc->p_exitthreads, 1);
			thread_unlink(td);
			td2 = FIRST_THREAD_IN_PROC(p);
			sched_exit_thread(td2, td);

			/*
			 * The test below is NOT true if we are the
			 * sole exiting thread. P_STOPPED_SINGLE is unset
			 * in exit1() after it is the only survivor.
			 */
			if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
				if (p->p_numthreads == p->p_suspcount) {
					thread_lock(p->p_singlethread);
					wakeup_swapper = thread_unsuspend_one(
						p->p_singlethread, p, false);
					if (wakeup_swapper)
						kick_proc0();
				}