linux-kernel - Re: context tracking vs. syscall_trace_leave & do_notify

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Message-ID: <5543A774.5010501@redhat.com>
Date:	Fri, 01 May 2015 12:19:00 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>
CC:	Fr馘駻ic Weisbecker <fweisbec@...il.com>,
	X86 <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Denys Vlasenko <dvlasenk@...hat.com>
Subject: Re: context tracking vs. syscall_trace_leave & do_notify_resume loop

On 05/01/2015 12:16 PM, Andy Lutomirski wrote:
> On Fri, May 1, 2015 at 9:14 AM, Rik van Riel <riel@...hat.com> wrote:
>> On 05/01/2015 12:05 PM, Andy Lutomirski wrote:
>>> On Fri, May 1, 2015 at 9:00 AM, Rik van Riel <riel@...hat.com> wrote:
>>
>>>> I suspect we probably only need two possible function
>>>> calls at syscall exit time:
>>>>
>>>> 1) A function that is called with interrupts still
>>>>    enabled, testing flags that could be set again
>>>>    if something happens (eg. preemption) between
>>>>    when the function is called, and we return to
>>>>    user space.
>>>>
>>>> 2) A function that is called after the point of
>>>>    no return, with interrupts disabled, which
>>>>    does (mostly) small things that only happen
>>>>    once.

> C can have loops just as easily as assembly can :)  I still don't see
> why we need magic asm code to schedule and deliver signals.  We
> certainly need to have valid pt_regs to deliver signals, but that's
> easy and much cheaper than it used to be.

Oh, I never said it would all have to be in assembly :)

I would love to see the stuff in entry.S greatly simplified.

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