linux-kernel - Re: [PATCH] arm64: reenable interrupt when handling ptrace breakpoint

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Message-ID: <20160113172303.GH25458@arm.com>
Date:	Wed, 13 Jan 2016 17:23:03 +0000
From:	Will Deacon <will.deacon@....com>
To:	"Shi, Yang" <yang.shi@...aro.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Catalin.Marinas@....com,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linaro-kernel@...ts.linaro.org, linux-rt-users@...r.kernel.org
Subject: Re: [PATCH] arm64: reenable interrupt when handling ptrace breakpoint

On Wed, Jan 13, 2016 at 09:17:46AM -0800, Shi, Yang wrote:
> On 1/13/2016 2:26 AM, Will Deacon wrote:
> >On Tue, Jan 12, 2016 at 11:59:54AM -0800, Shi, Yang wrote:
> >>This might be buried in email storm during the holiday. Just want to double
> >>check the status. I'm supposed there is no objection for getting it merged
> >>in upstream?
> >
> >Sorry, when you replied with:
> >
> >>I think we could just extend the "signal delay send" approach from x86-64
> >>to arm64, which is currently used by x86-64 on -rt kernel only.
> >
> >I understood that you were going to fix -rt, so I dropped this pending
> >anything more from you.
> >
> >What's the plan?
> 
> Sorry for the confusion. The "signal delay send" approach used by x86-64 -rt
> should be not necessary for arm64 right now. Reenabling interrupt is still
> the preferred approach.
> 
> Since x86-64 has per-CPU IST exception stack, so preemption has to be
> disabled all the time. However, it is not applicable to other architectures
> for now, including arm64.

Actually, we grew support for a separate IRQ stack in the recent merge
window. Does that change things here, or are you referring to something
else?

Will