Re: microcode_ctl question (fwd)

[Dave Jones <davej@redhat.com>]

On Thu, May 06, 2004 at 01:23:42PM +0100, Tigran Aivazian wrote:

Hi Tigran,

 > Btw, I have just noticed what may be a bug wrt not being aware of kernel
 > preemption, i.e. we cache the CPU id in a local variable and later use it,
 > but then there seems to be no protection against kernel preemption (i.e.
 > we hold no spinlocks, only a semaphore) at that point, so the original CPU
 > id may not be quite the same as the CPU id for which the data was
 > collected. I should fix this if it is a problem. The question to
 > linux-kernel guys is to confirm that this is indeed a bug, i.e. to clarify
 > under which condition the kernel preemption can and cannot occur.
 > 
 > In particular can such preemption occur while executing a function called 
 > via IPI mechanism?

I fixed up microcode.c to use on_each_cpu() last year sometime, which
I thought should fix things up wrt preemption. Can you point to the
bits you think are still problematic ?

		Dave