Function sysctl_kern_proc_kstack

freebsd/kern/kern_proc.c:2689–2771

#if defined(STACK) || defined(DDB)
static int
sysctl_kern_proc_kstack(SYSCTL_HANDLER_ARGS)
{
	struct kinfo_kstack *kkstp;
	int error, i, *name, numthreads;
	lwpid_t *lwpidarray;
	struct thread *td;
	struct stack *st;
	struct sbuf sb;
	struct proc *p;

	name = (int *)arg1;
	error = pget((pid_t)name[0], PGET_NOTINEXEC | PGET_WANTREAD, &p);
	if (error != 0)
		return (error);

	kkstp = malloc(sizeof(*kkstp), M_TEMP, M_WAITOK);
	st = stack_create(M_WAITOK);

	lwpidarray = NULL;
	PROC_LOCK(p);
	do {
		if (lwpidarray != NULL) {
			free(lwpidarray, M_TEMP);
			lwpidarray = NULL;
		}
		numthreads = p->p_numthreads;
		PROC_UNLOCK(p);
		lwpidarray = malloc(sizeof(*lwpidarray) * numthreads, M_TEMP,
		    M_WAITOK | M_ZERO);
		PROC_LOCK(p);
	} while (numthreads < p->p_numthreads);

	/*
	 * XXXRW: During the below loop, execve(2) and countless other sorts
	 * of changes could have taken place.  Should we check to see if the
	 * vmspace has been replaced, or the like, in order to prevent
	 * giving a snapshot that spans, say, execve(2), with some threads
	 * before and some after?  Among other things, the credentials could
	 * have changed, in which case the right to extract debug info might
	 * no longer be assured.
	 */
	i = 0;
	FOREACH_THREAD_IN_PROC(p, td) {
		KASSERT(i < numthreads,
		    ("sysctl_kern_proc_kstack: numthreads"));
		lwpidarray[i] = td->td_tid;
		i++;
	}
	PROC_UNLOCK(p);
	numthreads = i;
	for (i = 0; i < numthreads; i++) {
		td = tdfind(lwpidarray[i], p->p_pid);
		if (td == NULL) {
			continue;
		}
		bzero(kkstp, sizeof(*kkstp));
		(void)sbuf_new(&sb, kkstp->kkst_trace,