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From: "Shi, Yang" <yang.shi@linaro.org>
To: Will Deacon <will.deacon@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Catalin.Marinas@arm.com, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linaro-kernel@lists.linaro.org, linux-rt-users@vger.kernel.org
Subject: Re: [PATCH] arm64: reenable interrupt when handling ptrace breakpoint
Date: Fri, 5 Feb 2016 13:25:47 -0800	[thread overview]
Message-ID: <56B5135B.3050801@linaro.org> (raw)
In-Reply-To: <56969312.7070309@linaro.org>

On 1/13/2016 10:10 AM, Shi, Yang wrote:
> On 1/13/2016 9:23 AM, Will Deacon wrote:
>> 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?
>
> Had a quick look at the patches, it looks the irq stack is not nestable
> and it switches back to the original stack as long as irq handler is
> done before preempt happens. So, it sounds it won't change things here.


Just had a quick test on 4.5-rc1. It survives with kgdbts, ptrace and 
ltp. So, it sounds safe with the "separate IRQ stack" change.

Thanks,
Yang

>
> Thanks.,
> Yang
>
>>
>> Will
>>
>

WARNING: multiple messages have this Message-ID (diff)
From: yang.shi@linaro.org (Shi, Yang)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] arm64: reenable interrupt when handling ptrace breakpoint
Date: Fri, 5 Feb 2016 13:25:47 -0800	[thread overview]
Message-ID: <56B5135B.3050801@linaro.org> (raw)
In-Reply-To: <56969312.7070309@linaro.org>

On 1/13/2016 10:10 AM, Shi, Yang wrote:
> On 1/13/2016 9:23 AM, Will Deacon wrote:
>> 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?
>
> Had a quick look at the patches, it looks the irq stack is not nestable
> and it switches back to the original stack as long as irq handler is
> done before preempt happens. So, it sounds it won't change things here.


Just had a quick test on 4.5-rc1. It survives with kgdbts, ptrace and 
ltp. So, it sounds safe with the "separate IRQ stack" change.

Thanks,
Yang

>
> Thanks.,
> Yang
>
>>
>> Will
>>
>

  reply	other threads:[~2016-02-05 21:26 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-12-16  0:18 [PATCH] arm64: reenable interrupt when handling ptrace breakpoint Yang Shi
2015-12-16  0:18 ` Yang Shi
2015-12-16 11:13 ` Will Deacon
2015-12-16 11:13   ` Will Deacon
2015-12-16 20:45   ` Shi, Yang
2015-12-16 20:45     ` Shi, Yang
2015-12-21 10:48     ` Will Deacon
2015-12-21 10:48       ` Will Deacon
2015-12-21 16:51       ` Thomas Gleixner
2015-12-21 16:51         ` Thomas Gleixner
2015-12-21 17:00         ` Will Deacon
2015-12-21 17:00           ` Will Deacon
2015-12-21 17:27           ` Shi, Yang
2015-12-21 17:27             ` Shi, Yang
2016-01-12 19:59           ` Shi, Yang
2016-01-12 19:59             ` Shi, Yang
2016-01-13 10:26             ` Will Deacon
2016-01-13 10:26               ` Will Deacon
2016-01-13 10:26               ` Will Deacon
2016-01-13 17:17               ` Shi, Yang
2016-01-13 17:17                 ` Shi, Yang
2016-01-13 17:23                 ` Will Deacon
2016-01-13 17:23                   ` Will Deacon
2016-01-13 18:10                   ` Shi, Yang
2016-01-13 18:10                     ` Shi, Yang
2016-02-05 21:25                     ` Shi, Yang [this message]
2016-02-05 21:25                       ` Shi, Yang
2016-02-11 13:54                       ` Will Deacon
2016-02-11 13:54                         ` Will Deacon
2016-02-11 17:29                         ` Shi, Yang
2016-02-11 17:29                           ` Shi, Yang

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