HEAD UP: non-MPSAFE network drivers to be disabled (was: 8.0 network stack MPsafety goals (fwd))

Robert Watson rwatson at FreeBSD.org
Sat May 24 10:21:00 UTC 2008 

Dear all:

Just as a reminder, we've just about reached the one month date before 
IFF_NEEDSGIANT drivers are disabled in the build.  You can find a description 
of the general problem and list of specific drivers below.

As USB work is on-going, I will *not* disable the USB drivers at this time, 
but all other drivers in the list below will be disabled on 26 June.  They 
will remain in the tree, easily accessible for patch distribution and 
re-enabling, until October, when any remaining non-MPSAFE drivers will be 
deleted in 8.x.  FreeBSD 8.0 will not ship with compatibility shims to support 
non-MPSAFE network device drivers.

Robert N M Watson
Computer Laboratory
University of Cambridge

---------- Forwarded message ----------
Date: Sun, 3 Feb 2008 20:59:05 +0000 (GMT)
From: Robert Watson <rwatson at FreeBSD.org>
To: arch at FreeBSD.org
Subject: 8.0 network stack MPsafety goals (fwd)


Only a few days after predicted, this is a reminder that IFF_NEEDSGIANT network 
drivers are going to stop working in the forseeable future.  Please review the 
attached driver list, and if you depend on or care about a Giant-dependent 
device driver, take action to make sure it doesn't remain on the list in a 
month's time!

(As far as I'm aware, the list has not changed since my December posting.)

Robert N M Watson
Computer Laboratory
University of Cambridge

---------- Forwarded message ----------
Date: Mon, 24 Dec 2007 10:43:28 +0000 (GMT)
From: Robert Watson <rwatson at FreeBSD.org>
To: arch at FreeBSD.org
Subject: 8.0 network stack MPsafety goals


Dear all:

With the 7.0 release around the corner, many developers are starting to think 
about (and in quite a few cases, work on) their goals for 8.0.  One of our 
on-going kernel projects has been the elimination of the Giant lock, and that 
project has transformed into one of optimizating behavior on increasing numbers 
of processors.

In 7.0, despite the noteworth accomplishment of eliminating debug.mpsasfenet 
and conditional network stack Gian acquisition, we were unable to fully 
eliminate the IFF_NEEDSGIANT flag, which controls the conditional acquisition 
of the Giant lock around non-MPSAFE network device drivers.  Primarily these 
drivers are aging ISA network device drivers, although there are some 
exceptions, such as the USB stack.

This e-mail proposes the elimination of the IFF_NEEDSGIANT flag and associated 
infrastructure in FreeBSD 8.0, meaning that all network device drivers must be 
able to operate without the Giant lock (largely the case already).  Remaining 
drivers using the IFF_NEEDSGIANT flag must either be updated, or less ideally, 
removed.  I propose the following schedule:

Date		Goals
----		-----
26 Dec 2007	Post proposed schedule for flag and infrastructure removal
 		Post affected driver list

26 Jan 2008	Repost proposed schedule for flag and infrastructure removal
 		Post updated affected driver list

26 Feb 2008	Adjust boot-time printf for affect drivers to generate a loud
 		warning.
 		Post updated affected driver list

26 May 2008	Post HEADS UP of impending driver disabling
 		Post updated affected driver list

26 Jun 2008	Disable build of all drivers requiring IFF_NEEDSGIANT
 		Post updated affected driver list

26 Sep 2008	Post HEADS up of impending driver removal
 		Post updated affected driver list

26 Oct 2008	Delete source of all drivers requiring IFF_NEEDSGIANT
 		Remove flag and infrastructure

Here is a list of potentially affected drivers:

Name	Bus		Man page description
---	---		--------------------
ar	ISA/PCI		synchronous Digi/Arnet device driver
arl	ISA		Aironet Arlan 655 wireless network adapter driver
awi	PCCARD		AMD PCnetMobile IEEE 802.11 PCMCIA wireless network
 			driver
axe	USB		ASIX Electronics AX88172 USB Ethernet driver
cdce	USB		USB Communication Device Class Ethernet driver
cnw	PCCARD		Netwave AirSurfer wireless network driver
cs	ISA/PCCARD	Ethernet device driver
cue	USB		CATC USB-EL1210A USB Ethernet driver
ex	ISA/PCCARD	Ethernet device driver for the Intel EtherExpress
 			Pro/10 and Pro/10+
fe	CBUS/ISA/PCCARD	Fujitsu MB86960A/MB86965A based Ethernet adapters
ic	I2C		I2C bus system
ie	ISA		Ethernet device driver
kue	USB		Kawasaki LSI KL5KUSB101B USB Ethernet driver
oltr	ISA/PCI		Olicom Token Ring device driver
plip	PPBUS		printer port Internet Protocol driver
ppp	TTY		point to point protocol network interface
ray	PCCARD		Raytheon Raylink/Webgear Aviator PCCard driver
rue	USB		RealTek RTL8150 USB to Fast Ethernet controller driver
rum	USB		Ralink Technology USB IEEE 802.11a/b/g wireless
 			network device
sbni	ISA/PCI		Granch SBNI12 leased line modem driver
sbsh	PCI		Granch SBNI16 SHDSL modem device driver
sl	TTY		slip network interface
snc	ISA/PCCARD	National Semiconductor DP8393X SONIC Ethernet adapter
 			driver
sr	ISA/PCI		synchronous RISCom/N2 / WANic 400/405 device driver
udav	USB		Davicom DM9601 USB Ethernet driver
ural	USB		Ralink Technology RT2500USB IEEE 802.11 driver
xe	PCCARD		Xircom PCMCIA Ethernet device driver
zyd	USB		ZyDAS ZD1211/ZD1211B USB IEEE 802.11b/g wireless
 			network device

In some cases, the requirement for Giant is a property of a subsystem the 
driver depends on as the driver itself; for example, the tty subsystem for SLIP 
and PPP, and the USB subsystem for a number of USB ethernet and wireless 
drivers.  With most of a year before to go on the proposed schedule, my hope is 
that we will have lots of time to address these issues, but wanted to get a 
roadmap out from a network protocol stack architecture perspective so that 
device driver and subsystem authors could have a schedule in mind.

FYI, the following drivers also reference IFF_NEEDSGIANT, but only in order to 
provide their own conditional MPSAFEty, which can be removed without affecting 
device driver functionality (I believe):

Name	Bus		Man page description
---	---		--------------------
ce	PCI		driver for synchronous Cronyx Tau-PCI/32 WAN adapters
cp	PCI		driver for synchronous Cronyx Tau-PCI WAN adapters
ctau	ISA		driver for synchronous Cronyx Tau WAN adapters
cx	ISA		driver for synchronous/asynchronous Cronyx Sigma WAN
 			adapters

Developers and users of the above drivers are heavily encouraged to update the 
drivers to remove dependence on Giant, and/or make other contingency plans.

Robert N M Watson
Computer Laboratory
University of Cambridge
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