About interrupt handler

About interrupt handler

[cheneydeng]

hi all,
     I'm begin to learn the Kernel and i'm reading <<Linux kernel development>>.It says "This is an important point, always keep in mind that all interrupt handler has interrupted other code(possibly even another interrupt handler on a different line)".What i am not able to understand is how a interrupt handler be interrupted ? DID NOT it uninterrupted?


------------------
best regards?
  cheneydeng
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About interrupt handler

[Dave Hylands]

Hi cheneydeng,

2012/2/22 cheneydeng <cheneydeng@qq.com>:
> hi all,
> ? ? ?I'm begin to learn the Kernel and i'm reading <<Linux kernel
> development>>.It says "This is an important point, always keep in mind that
> all interrupt handler has interrupted other code(possibly even another
> interrupt handler on a different line)".What i am not able to understand is
> how a interrupt handler be interrupted ? DID NOT it uninterrupted?

It depends on the architecture and the interrupt controller being
used, and the driver code itself.

Normally, when an interrupt fires, that particular interrupt will be
masked and your own handler won't interrupt itself, but you may very
well be interrupted by other interrupts.

It is possible to arrange things so that your interrupt handler
interrupts itself, although you need to be really careful when doing
this as if your interrupt fires too quickly things can escalate out of
control pretty quickly.

-- 
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com

About interrupt handler

[Kosta Zertsekel]

>> I'm begin to learn the Kernel and i'm reading <<Linux kernel
>> development>>.It says "This is an important point, always keep in mind that
>> all interrupt handler has interrupted other code(possibly even another
>> interrupt handler on a different line)".What i am not able to understand is
>> how a interrupt handler be interrupted ? DID NOT it uninterrupted?
>
> It depends on the architecture and the interrupt controller being
> used, and the driver code itself.
>
> Normally, when an interrupt fires, that particular interrupt will be
> masked and your own handler won't interrupt itself, but you may very
> well be interrupted by other interrupts.

Can you please point out some code for explanation?
--- KostaZ

About interrupt handler

[Dave Hylands]

Hi Kosta,

On Fri, Feb 24, 2012 at 1:19 AM, Kosta Zertsekel <zertsekel@gmail.com> wrote:
>>> I'm begin to learn the Kernel and i'm reading <<Linux kernel
>>> development>>.It says "This is an important point, always keep in mind that
>>> all interrupt handler has interrupted other code(possibly even another
>>> interrupt handler on a different line)".What i am not able to understand is
>>> how a interrupt handler be interrupted ? DID NOT it uninterrupted?
>>
>> It depends on the architecture and the interrupt controller being
>> used, and the driver code itself.
>>
>> Normally, when an interrupt fires, that particular interrupt will be
>> masked and your own handler won't interrupt itself, but you may very
>> well be interrupted by other interrupts.
>
> Can you please point out some code for explanation?

Could you be a bit more specific about what example you're looking for?

-- 
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com

About interrupt handler

[Dave Hylands]

HI Kosta,

On Fri, Feb 24, 2012 at 1:08 PM, Dave Hylands <dhylands@gmail.com> wrote:
> Hi Kosta,
>
> On Fri, Feb 24, 2012 at 1:19 AM, Kosta Zertsekel <zertsekel@gmail.com> wrote:
>>>> I'm begin to learn the Kernel and i'm reading <<Linux kernel
>>>> development>>.It says "This is an important point, always keep in mind that
>>>> all interrupt handler has interrupted other code(possibly even another
>>>> interrupt handler on a different line)".What i am not able to understand is
>>>> how a interrupt handler be interrupted ? DID NOT it uninterrupted?
>>>
>>> It depends on the architecture and the interrupt controller being
>>> used, and the driver code itself.
>>>
>>> Normally, when an interrupt fires, that particular interrupt will be
>>> masked and your own handler won't interrupt itself, but you may very
>>> well be interrupted by other interrupts.
>>
>> Can you please point out some code for explanation?
>
> Could you be a bit more specific about what example you're looking for?

I also believe that things have changed (since I looked at this in any
detail). It seems that interrupts are now run with other interrupts
disabled.
See: http://lwn.net/Articles/364583/ and look at the IRQF_DISABLED discussion.

-- 
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com

About interrupt handler

[Kosta Zertsekel]

On Fri, Feb 24, 2012 at 11:18 PM, Dave Hylands <dhylands@gmail.com> wrote:
> HI Kosta,
>
> On Fri, Feb 24, 2012 at 1:08 PM, Dave Hylands <dhylands@gmail.com> wrote:
>> Hi Kosta,
>>
>> On Fri, Feb 24, 2012 at 1:19 AM, Kosta Zertsekel <zertsekel@gmail.com> wrote:
>>>>> I'm begin to learn the Kernel and i'm reading <<Linux kernel
>>>>> development>>.It says "This is an important point, always keep in mind that
>>>>> all interrupt handler has interrupted other code(possibly even another
>>>>> interrupt handler on a different line)".What i am not able to understand is
>>>>> how a interrupt handler be interrupted ? DID NOT it uninterrupted?
>>>>
>>>> It depends on the architecture and the interrupt controller being
>>>> used, and the driver code itself.
>>>>
>>>> Normally, when an interrupt fires, that particular interrupt will be
>>>> masked and your own handler won't interrupt itself, but you may very
>>>> well be interrupted by other interrupts.
>>>
>>> Can you please point out some code for explanation?
>>
>> Could you be a bit more specific about what example you're looking for?
>
> I also believe that things have changed (since I looked at this in any
> detail). It seems that interrupts are now run with other interrupts
> disabled.
> See: http://lwn.net/Articles/364583/ and look at the IRQF_DISABLED discussion.

Oh, yes, it seems it does as of kernel 3.3.0. But I fail to accept the
argument...
What happens for NAPI drivers stalling the kernel - *nobody* can
interrupt them...
Is there some reliable IRQ deep dive explanation - I need one just to
wrap my mind over the issue?
Thanks,
--- KostaZ

About interrupt handler

[Dave Hylands]

Hi Kosta,

On Sun, Feb 26, 2012 at 4:11 AM, Kosta Zertsekel <zertsekel@gmail.com> wrote:
> On Fri, Feb 24, 2012 at 11:18 PM, Dave Hylands <dhylands@gmail.com> wrote:
>> HI Kosta,
>>
>> On Fri, Feb 24, 2012 at 1:08 PM, Dave Hylands <dhylands@gmail.com> wrote:
>>> Hi Kosta,
>>>
>>> On Fri, Feb 24, 2012 at 1:19 AM, Kosta Zertsekel <zertsekel@gmail.com> wrote:
>>>>>> I'm begin to learn the Kernel and i'm reading <<Linux kernel
>>>>>> development>>.It says "This is an important point, always keep in mind that
>>>>>> all interrupt handler has interrupted other code(possibly even another
>>>>>> interrupt handler on a different line)".What i am not able to understand is
>>>>>> how a interrupt handler be interrupted ? DID NOT it uninterrupted?
>>>>>
>>>>> It depends on the architecture and the interrupt controller being
>>>>> used, and the driver code itself.
>>>>>
>>>>> Normally, when an interrupt fires, that particular interrupt will be
>>>>> masked and your own handler won't interrupt itself, but you may very
>>>>> well be interrupted by other interrupts.
>>>>
>>>> Can you please point out some code for explanation?
>>>
>>> Could you be a bit more specific about what example you're looking for?
>>
>> I also believe that things have changed (since I looked at this in any
>> detail). It seems that interrupts are now run with other interrupts
>> disabled.
>> See: http://lwn.net/Articles/364583/ and look at the IRQF_DISABLED discussion.
>
> Oh, yes, it seems it does as of kernel 3.3.0. But I fail to accept the
> argument...
> What happens for NAPI drivers stalling the kernel - *nobody* can
> interrupt them...
> Is there some reliable IRQ deep dive explanation - I need one just to
> wrap my mind over the issue?

Well the kernel has the ability to use threaded irqs. This allows IRQs
to be given a proirity so you can allow one interrupt to interrupt
another or to even allow threads to interrupt interrupts.

http://lwn.net/Articles/302043/
http://www.artist-embedded.org/docs/Events/2009/OSPERT/OSPERT09-Henriques.pdf
http://elinux.org/images/e/ef/InterruptThreads-Slides_Anderson.pdf

-- 
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com

About interrupt handler

[cheneydeng]

Thanks to all of you~


------------------
best regards?
  cheneydeng
 

 
 
 
------------------ Original ------------------
From:  "Zhengwang Ruan"<ruan.zhengwang@gmail.com>;
Date:  Thu, Feb 23, 2012 06:07 PM
To:  "kernelnewbies"<kernelnewbies@kernelnewbies.org>; 

Subject:  Re: About interrupt handler

 
                   
       
       
       -------- Original Message --------
       From: cheneydeng
       Sent: 2012?02?22? ??? 23?38?37?
       To: kernelnewbies
       Subject: About interrupt handler
                          hi all,
              I'm begin to learn the Kernel and i'm reading           <<Linux kernel development>>.It says "This is an           important point, always keep in mind that all interrupt           handler has interrupted other code(possibly even another           interrupt handler on a different line)".What i am not able to           understand is how a interrupt handler be interrupted ? DID NOT           it uninterrupted?
       
          
     It has more related to CPU architecture. Generally, while an     interrupt handler is being executed, the handler itself can chose to     disable or enable external interrupts (i.e, take x86 for example, IF     bit for cflags reg controls this.). If IF is enabled, then the     interrupt handler currently being executed may be interrupted and     then jump to the entry for the coming interrupt.
     
     Thanks,
         -Zhengwang
     
     
                     
         
                      ------------------
                            best regards?
                 cheneydeng
             
           
          
       
        _______________________________________________ Kernelnewbies mailing list Kernelnewbies at kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
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About interrupt handler

[Zhengwang Ruan]

-------- Original Message --------
From: cheneydeng
Sent: 2012?02?22? ??? 23?38?37?
To: kernelnewbies
Subject: About interrupt handler
> hi all,
> I'm begin to learn the Kernel and i'm reading <<Linux kernel
> development>>.It says "This is an important point, always keep in mind
> that all interrupt handler has interrupted other code(possibly even
> another interrupt handler on a different line)".What i am not able to
> understand is how a interrupt handler be interrupted ? DID NOT it
> uninterrupted?

It has more related to CPU architecture. Generally, while an interrupt
handler is being executed, the handler itself can chose to disable or
enable external interrupts (i.e, take x86 for example, IF bit for cflags
reg controls this.). If IF is enabled, then the interrupt handler
currently being executed may be interrupted and then jump to the entry
for the coming interrupt.

Thanks,
-Zhengwang


>
> ------------------
> best regards?
> cheneydeng
>
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies

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About interrupt handler

[cheneydeng]

hi all,
     I'm begin to learn the Kernel and i'm reading <<Linux kernel development>>.It says "This is an important point, always keep in mind that all interrupt handler has interrupted other code(possibly even another interrupt handler on a different line)".What i am not able to understand is how a interrupt handler be interrupted ? DID NOT it uninterrupted?


------------------
best regards?
  cheneydeng
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