Re: [patch] use valid value when unmapping cpus

[Matthew Dobson <colpatch@us.ibm.com>]

Matt Mackall wrote:
> On Wed, Jun 04, 2003 at 02:26:22PM -0700, Matthew Dobson wrote:
> 
>>For some unknown reason, we stick a -1 in cpu_2_node when we unmap a cpu 
>>on i386.  We're better off sticking a 0 in there, because at least 0 is 
>>a valid value if something references it.  -1 is only going to cause 
>>problems at some point down the line.
> 
> 
> Problems down the line help you find the bogus dereference. Even
> better to stick a poison value in there.

Well, it's not really a dereference issue.  The function, cpu_to_node() 
just returns an integer which is the node that particular CPU is on. 
This should always return a valid value.  This is used in many places, 
often as a direct index into an array, and we shouldn't have to check 
its return value everywhere.  The default behavior is to just return 0, 
because 0 is a valid node, even for UP/SMP.  The array of CPU -> node 
mappings is initialized to 0's on i386 already, so unmapping a CPU 
should return this mapping to its uninitialized state.

Cheers!

-Matt