Re: [patch] use valid value when unmapping cpus

From: Matthew Dobson (
Date: Mon Jun 09 2003 - 11:59:52 EST

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.



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