From owner-freebsd-arch@FreeBSD.ORG  Sat Mar 22 11:12:54 2008
Return-Path: <owner-freebsd-arch@FreeBSD.ORG>
Delivered-To: arch@FreeBSD.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id A5CD21065677
	for <arch@FreeBSD.org>; Sat, 22 Mar 2008 11:12:54 +0000 (UTC)
	(envelope-from rermilov@team.vega.ru)
Received: from mail.vega.ru (infra.dev.vega.ru [90.156.167.14])
	by mx1.freebsd.org (Postfix) with ESMTP id 5EA848FC15
	for <arch@FreeBSD.org>; Sat, 22 Mar 2008 11:12:53 +0000 (UTC)
	(envelope-from rermilov@team.vega.ru)
Received: from [87.242.97.68] (port=55671 helo=edoofus.dev.vega.ru)
	by mail.vega.ru with esmtpsa (TLSv1:AES256-SHA:256)
	(Exim 4.68 (FreeBSD)) (envelope-from <rermilov@team.vega.ru>)
	id 1Jd1KI-0001Qu-Mj
	for arch@FreeBSD.org; Sat, 22 Mar 2008 10:51:50 +0000
Received: from edoofus.dev.vega.ru (localhost [127.0.0.1])
	by edoofus.dev.vega.ru (8.14.2/8.14.2) with ESMTP id m2MApjEB041826
	for <arch@FreeBSD.org>; Sat, 22 Mar 2008 13:51:45 +0300 (MSK)
	(envelope-from rermilov@team.vega.ru)
Received: (from ru@localhost)
	by edoofus.dev.vega.ru (8.14.2/8.14.2/Submit) id m2MApjDr041825
	for arch@FreeBSD.org; Sat, 22 Mar 2008 13:51:45 +0300 (MSK)
	(envelope-from rermilov@team.vega.ru)
X-Authentication-Warning: edoofus.dev.vega.ru: ru set sender to
	rermilov@team.vega.ru using -f
Date: Sat, 22 Mar 2008 13:51:45 +0300
From: Ruslan Ermilov <ru@FreeBSD.org>
To: arch@FreeBSD.org
Message-ID: <20080322105145.GA41672@team.vega.ru>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
User-Agent: Mutt/1.5.17 (2007-11-01)
Cc: 
Subject: Disposal of a misleading M_TRYWAIT
X-BeenThere: freebsd-arch@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussion related to FreeBSD architecture <freebsd-arch.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-arch>,
	<mailto:freebsd-arch-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-arch>
List-Post: <mailto:freebsd-arch@freebsd.org>
List-Help: <mailto:freebsd-arch-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-arch>,
	<mailto:freebsd-arch-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sat, 22 Mar 2008 11:12:54 -0000

I'd like to remove the misleading uses of M_TRYWAIT throughout
the tree and clean up some dead code that assumes its original
behavior (that it could return NULL).

Since the advent of MBUMA in FreeBSD (whatever), M_TRYWAIT has
meant M_WAITOK.  (The reason for M_TRYWAIT itself was that an
original mbuf's M_WAIT could return NULL.)

There is little or no sign that this will change, and there are
lots of consumers that already pass M_WAITOK to mbuf allocator
routines and rely on its invariants, so support for the concept
of M_TRYWAIT has rotted and would have to be re-written anyway
if reintroduced.

http://people.freebsd.org/~ru/patches/M_TRYWAIT.patch


Cheers,
-- 
Ruslan Ermilov
ru@FreeBSD.org
FreeBSD committer