Re: [PATCH 1/2] x86: stop using PER_CPU_VAR(kernel_stack)

From: Denys Vlasenko
Date: Mon Mar 23 2015 - 13:10:36 EST


On 03/23/2015 03:18 PM, Steven Rostedt wrote:
> On Sat, 21 Mar 2015 21:44:37 +0100
> Denys Vlasenko <dvlasenk@xxxxxxxxxx> wrote:
>
>> Instead of PER_CPU_VAR(kernel_stack), 64-bit code
>> can use PER_CPU_VAR(cpu_tss + TSS_sp0).
>
> The change log here is lacking an answer to "why". It only states what
> it does. What's wrong with using kernel_stack? The change log should
> explicitly state that. I have no idea why this patch is needed.

Sorry. The reason is:

We want to get rid of kernel_stack, since it is redundant:
in 64-bits, PER_CPU_VAR(cpu_tss + TSS_sp0) can be used instead,
in 32-bits, PER_CPU_VAR(cpu_current_top_of_stack) can be used instead.

Patch 2/2 in the same series removes kernel_stack.
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