Re: [PATCH] fix strange stack calculation for secondary cpus

[Dave Hansen <haveblue@us.ibm.com>]

Hugh Dickins wrote:
> On Tue, 10 Dec 2002, Dave Hansen wrote:
> 
>>in arch/i386/kernel/smpboot.c:
>>stack_start.esp = (void *) (1024 + PAGE_SIZE + (char *)idle);
>>
>>This causes problems when I switch to 4k stacks?  What is supposed to 
>>be going on here?  Why point esp into the middle of the stack?  If you 
>>wanted to do that, why not just use PAGE_SIZE>>2?
>>
> To avoid mysterious magic numbers, I chose instead to start it immediately
> below that area i.e. set the top esp here to the bottom esp there.  That
> worked fine for 2.4, I don't see why the same shouldn't work for 2.5.

It should.  I just want to be able to use arbitrary stack sizes.

> Whereas with your patch, you might be overwriting that area.
> So below I've munged your patch into what we found worked back then.

Agreed.  I was really just trying to eliminate the magic number 
without much real knowledge about what was going on.

Would you like to send your patch on to Alan or Linus?
-- 
Dave Hansen
haveblue@us.ibm.com