Re: kernel preemption does not work

[Scott Lovenberg <scott.lovenberg@xxxxxxxxx>]

Peter Teoh wrote:

On Fri, Apr 11, 2008 at 4:57 PM, Scott Lovenberg
<scott.lovenberg@xxxxxxxxx> wrote:
  

 Yeah, FWIW, none of the server distros compile preemption in; it's only
really for desktop responsiveness, and even then, I think its value may be
marginal (at this time - I think it will mature).  I'm not sure exactly how
it works, but there is also a BIG_KERNEL_LOCK or something to that effect...
that's probably a spinlock thing.  I've never ventured to that part of the
code base, yet.  Peter, do you know anything about it?  I think it showed up
    

Not sure what u mean.   But in init/Kconfig is this:

config LOCK_KERNEL
        bool
        depends on SMP || PREEMPT
        default y

So CONFIG_LOCK_KERNEL will require that CONFIG_PREEMPT to be turned
on, or CONFIG_SMP.

For embedded CONFIG_SMP may not be y, so if CONFIG_LOCK_KERNEL is to
be default (y), then upon "make oldconfig" time u will be prompted to
turned on CONFIG_PREEMPT.

  

last summer or so as an unstable compile option.  Or, that's the first time
I stumbled upon it :)

 Are you sure that they keyboard IRQs aren't masked?  I think PCI steering
reroutes them to like IRQ 17 or so, but they should be on a shared IRQ,
IIRC.

    

Sorry it took me so long to get back to this (I've been swamped lately)...
I managed to pull this from IBM's Anatomy of Linux synchronization methods:

Finally, there remains the big kernel lock (BKL). Its use in the kernel is diminishing, but the remaining uses are the most difficult to remove. The BKL made multiprocessor Linux possible, but finer-grained locks have slowly replaced the BKL. The BKL is provided through the functions lock_kernel and unlock_kernel. See ./linux/lib/kernel_lock.c for more information.



I've got a git pull going right now, I'm going to check this out.  Could you guys look at it as well so if I have any questions, someone else is a bit familiar with this bit of code? 

begin:vcard
fn:Scott Lovenberg
n:Lovenberg;Scott
org:The CleftStone Works
adr:;;;Kutztown;PA;19530;USA
email;internet:scott.lovenberg@xxxxxxxxx
tel;cell:570-856-2999
note;quoted-printable:Interests:=0D=0A=
	Programming, *NIX, Slackware, Samba, C/C++, Perl, Java, .NET, Kernel Hack=
	ing, Virtual Machines, FOSS, Security, Operating Systems, Various Softwar=
	e Stacks.  =
	=0D=0A=
	=0D=0A=
	Always have time for "shop talk"; feel free to drop me a line.
x-mozilla-html:TRUE
url:www.cleftstoneworks.com
version:2.1
end:vcard