Xref: utzoo comp.bugs.sys5:725 comp.unix.wizards:13693
Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!ukma!gatech!ulysses!smb
From: smb@ulysses.homer.nj.att.com (Steven M. Bellovin)
Newsgroups: comp.bugs.sys5,comp.unix.wizards
Subject: Re: Surprising fact about STREAMS service modules
Message-ID: <11047@ulysses.homer.nj.att.com>
Date: 25 Dec 88 20:31:18 GMT
References: <4385@hcr.UUCP> <313@taniwha.UUCP>
Organization: AT&T Bell Laboratories, Murray Hill
Lines: 7

A persistent bug source, in many versions on the UNIX system, is that
splN() calls, other than splx(), unconditionally set the interrupt
level to the indicated value, rather than *raising* it to that value.
It is almost never correct to lower an interrupt level, except via
splx() or spl0().  Sun has gotten some of those right; the symbolic
spl() calls (splimp(), etc.) check the current level before raising it.
4.3bsd is wrong; I haven't been able to check 4.3 Tahoe yet.