Re: HEADSUP: MPSAFE network drivers

On Thursday 30 October 2003 01:22 am, Pawel Jakub Dawidek wrote:
> On Wed, Oct 29, 2003 at 11:52:48AM -0700, Sam Leffler wrote:
> +> I'm committing changes to mark various network drivers' interrupt
> handlers +> MPSAFE. To insure folks have a way to backout if they hit
> problems I've also +> added a tunable that lets you disable this w/o
> rebuilding your kernel.  By +> default all network drivers that register an
> interrupt handler INTR_MPSAFE +> are setup to run their ISR w/o Giant.  If
> you want to defeat this w/o +> changing the code you can set
> +>
> +> debug.mpsafenet=0
> +>
> +> from the loader when booting and the MPSAFE bit will automatically be
> removed. +> I plan to use this to also control forthcoming changes for
> registering MPSAFE +> netisrs.
> +>
> +> The following drivers are marked MPSAFE:
> +>
> +> ath, em, ep, fxp, sn, wi, sis
> +>
> +> I've got changes coming for bge.  Other drivers probably can be marked
> MPSAFE +> but I'm only doing it for those drivers that I can test.
>
> Because there is so many drivers, maybe you could prepare some regression
> tests designed to check changed things. This will allow people to test your
> changes - it is not very easy now if we don't know what we're looking for
> exactly PLUS those drivers aren't marked MPSAFE by default.

Unfortunately there is no easy way to decide if the locking in a driver is 
correct; otherwise I'd simply test them and not provide a fallback as a I 
did.  Before I commit any driver I run with it for at least a few weeks (in 
some cases months) on a variety of machines (workstation, server, laptop, 
firewall).  If there are no problems then I commit the change.  The driver 
changes I committed yesterday I've been running for >4 months.  Likewise, the 
next round of locking changes to push Giant up have been running for ~2 
months.

Otherwise the main safeguard I use are numerous assertions to validate 
assumptions.

	Sam