Re: updating COMPAT_LINUX for linux 2.6.x support (take 2)

[Thor Lancelot Simon <tls%panix.com@localhost>]

On Thu, Jun 17, 2010 at 12:07:43PM -0400, Matthew Mondor wrote:
> On Thu, 17 Jun 2010 10:25:59 +0000
> Andrew Doran <ad%NetBSD.org@localhost> wrote:
> 
> > This is mainly down the fact that we need kernel_lock to bracket "legacy"
> > sections of code that aren't preemption safe.  I think MULTIPROCESSOR
> > should be sent off to the glue factory but that's another discussion :-).
> 
> Is there any way that performance for the uniprocessor case could be
> preserved, where some synchronization/preemption-safe blocks are
> unnecessary, without having conditional code when MULTIPROCESSOR?

Generally speaking, performance for the uniprocessor case is, in fact,
preserved, because the actual bus-locking operations are patched away
at startup time.

However, only x86 currently supports this, I believe.  Very similar code
is required by part of DTrace (FBT) and I wish someone had both the time
and the skills to work on it for more architectures.  But that's not me.

Thor