On 3/9/07, Arjan van de Ven <arjan@xxxxxxxxxxxxx> wrote:
CMIIW, when preempt is enabled , lock_kernel() will disable preempt.
Ok Sir.On Fri, 2007-03-09 at 06:20 +0000, my linux wrote:
>
> On 3/8/07, Arjan van de Ven <arjan@xxxxxxxxxxxxx> wrote:
> On Tue, 2007-03-06 at 11:25 +0000, my linux wrote:
> > Hi,
> >
> > How can I know whether my machine booted with SMP and
> non-SMP
> > kernel ? ( from kernel space)
>
> that sounds like a weird thing to care about; drivers or
> anything but
> deep architecture code really shouldn't have this knowledge!
>
> (for example preempt kernels basically make you have the same
> rules as
> smp anyway)
>
>
> #ifdef CONFIG_SMP
> lock_kernel();
> #endif
>
> #ifdef CONFIG_PREEMPT
> preempt_disable();
> #endif
>
> Is equivalant to
>
> lock_kernel();
> preempt_disable();
>
> in UP/SMP and preempt/non-preempt configuration ?
no, in fact your ifdefs are really incorrect.
the kernel makes those things no-ops IF THEY ARE. But your lock_kernel()
ifdef for example is really wrong if preempt is enabled!
CMIIW, when preempt is enabled , lock_kernel() will disable preempt.
(also, don't use lock_kernel() in new code anyway)
Also could you please elaborate little more on what is "wrong" with the ifdefs. Since I started working on linux few weeks back. :(
-mln
