linux-kernel - Re: [PATCH 3/4] x86: Rewrite switch

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Message-ID: <CAMzpN2hU8pFYqtuDNSW3E-nCnWqNZ_mVMhRN1cpkCWcOfyanLQ@mail.gmail.com>
Date:	Wed, 15 Jun 2016 07:52:55 -0400
From:	Brian Gerst <brgerst@...il.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Andy Lutomirski <luto@...capital.net>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Borislav Petkov <bp@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 3/4] x86: Rewrite switch_to() code

On Wed, Jun 15, 2016 at 4:03 AM, Ingo Molnar <mingo@...nel.org> wrote:
>
> * Andy Lutomirski <luto@...capital.net> wrote:
>
>> On Sat, May 21, 2016 at 9:04 AM, Brian Gerst <brgerst@...il.com> wrote:
>>
>> > Move the low-level context switch code to an out-of-line asm stub instead of
>> > using complex inline asm.  This allows constructing a new stack frame for the
>> > child process to make it seamlessly flow to ret_from_fork without an extra
>> > test and branch in __switch_to().  It also improves code generation for
>> > __schedule() by using the C calling convention instead of clobbering all
>> > registers.
>>
>> Just a heads up: I'm writing some code that conflicts with this patch. The
>> conflict will be easy to resolve, and, if this patch beats mine to -tip, I'll
>> rebase.
>
> So I was expecting another iteration of this switch_to() series, but had no
> fundamental objections to the concept.

I'll have it ready soon.  I've just been busy with other things lately.

--
Brian Gerst