On Mon, Sep 14, 2009 at 7:00 PM, Pei Lin <telent997@xxxxxxxxx> wrote:
hi , i didn't receive these messages. (^-^)> On Mon, Sep 14, 2009 at 4:01 PM, Leonidas . <leonidas137@xxxxxxxxx> wrote:
>>
>>
>> On Mon, Sep 14, 2009 at 3:32 PM, Leonidas . <leonidas137@xxxxxxxxx> wrote:
>>>
>>>
>>> On Mon, Sep 14, 2009 at 3:28 PM, Leonidas . <leonidas137@xxxxxxxxx>
>>> wrote:
>>>>
>>>>
>>>> On Mon, Sep 14, 2009 at 2:46 PM, karunakar rao
>>>> <karunakar.santhu@xxxxxxxxx> wrote:
>>>>>
>>>>> hi leo
>>>>> maintain circular buffer in module, so that if user doesn't access for
>>>>> days its going to be automatically discarded.I think printk also use same
>>>>> kind of mechanism which dumps data into cirbuffer.
>>>>>
>>>>> thanks,
>>>>> karuna.
>>>>>
>>>>> On Mon, Sep 14, 2009 at 2:41 PM, Leonidas . <leonidas137@xxxxxxxxx>
>>>>> wrote:
>>>>>>
>>>>>>
>>>>>> On Mon, Sep 14, 2009 at 2:30 PM, karunakar rao
>>>>>> <karunakar.santhu@xxxxxxxxx> wrote:
>>>>>>>
>>>>>>> hi leo
>>>>>>> you can maintain buffer in your module to log errors.When user tries
>>>>>>> to access /proc you can print all those from your buffer.
>>>>>>>
>>>>>>> Thanks,
>>>>>>> karuna.
>>>>>>>
>>>>>>> On Mon, Sep 14, 2009 at 1:22 PM, Leonidas . <leonidas137@xxxxxxxxx>
>>>>>>> wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>> Hi List
>>>>>>>>
>>>>>>>> I have written a kernel module which implements a char device. An
>>>>>>>> userspace app
>>>>>>>> is supposed to get data from my module and then dump it into a file
>>>>>>>> for further processing.
>>>>>>>>
>>>>>>>> The kind of data which kernel module is going to pass to userspace
>>>>>>>> is going to be a 4K buffer,
>>>>>>>> and the data traffic is not going to be really heavy, meaning may be
>>>>>>>> a 4K buffer every 1 min or so.
>>>>>>>> I am not very sure though, but certainly not heavy traffic the way
>>>>>>>> they describe for network traffic etc.
>>>>>>>>
>>>>>>>> And this data needs to be logged to a file either from kernel or
>>>>>>>> userspace and an userspace all will work
>>>>>>>> on that data. This data needs to be logged as soon as it arrives
>>>>>>>> meaning, I might not be able to write it to
>>>>>>>> /proc since from module I can update /proc only when user actually
>>>>>>>> accesses it. This data needs to be
>>>>>>>> static in nature, meaning I get one error and I write it to a file
>>>>>>>> somehow and user can see it anytime.
>>>>>>>>
>>>>>>>> I hope I have described the situation clearly. I have explored some
>>>>>>>> mechanism like ioctls, mmaping the
>>>>>>>> kernel buffer etc but all these would require the user module to
>>>>>>>> poll or notified somehow by kernel that
>>>>>>>> the data is available. I dont want the user module to poll.
>>>>>>>>
>>>>>>>>
>>>>>>>> -Leo.
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>> Pei Lin,
>>>>>>
>>>>>> I am not limiting my solution by using a law or what someone says. But
>>>>>> I think it is very important to
>>>>>> follow the spirit of environment/OS/arch you are working on and come
>>>>>> up with the best possible solution.
yeah,u can choose the way u wanna go,no matter a wide road or some
private alleys.
which one is convenient for different guys.
yeah,i agree. If it is a commercial software, it need a pretty and
>>>>>> As you correctly mention we can hack around and achieve the same
>>>>>> functionality but I would rather do these
>>>>>> kind of experiments for fun or to show my friends that the kernel can
>>>>>> be hacked these ways, but certainly not
>>>>>> in a system which is supposed to be a production system. I appreciate
>>>>>> your thoughts and I am sure many times
>>>>>> one stumbles upon real cool things which change course of nature and
>>>>>> are reasons for radical changes in
>>>>>> various subsystems. But I think this is not one of them, this has been
>>>>>> discussed over and over again and there
>>>>>> are standard interfaces defined. My questions is more about the design
>>>>>> part not about how I can hack and get
>>>>>> the stuff done.
clean interface to support future updating and maintenance.
i think use sockets like using a big hammer knock to small
>>>>>>
>>>>>> Karuna,
>>>>>> I had thought about this solution i.e. maintain a buffer in module and
>>>>>> dump it whenever user wants, only
>>>>>> issue is my module will keep consuming memory here. I msg buffers can
>>>>>> be freed once logged but how about
>>>>>> a case where user does not request for few days? The amount of memory
>>>>>> my module is going to consume will be
>>>>>> unacceptable.
>>>>>>
>>>>>> -Leo
>>>>>
>>>>
>>>> Sorry I did not mention it earlier, I can not discard any error message
>>>> logged, meaning these are error messages
>>>> and might crash my system after a long time. I need to to be able to see
>>>> all these messages till I restart my module.
>>>>
>>>> _Leo.
>>>
>>>
>>> Basically, I am quite tight on memory and I would like to convery error
>>> messages to user as soon as any
>>> error condition is hit. So my module cant keep even 10 error msg which
>>> will eat up 10 pages.
>>>
>>> _Leo
>>>
>>>
>>
>> Looks like some of the replys didn't get delivered to the list. Please
>> refer the thread for someof the interactions.
>>
>> Isn't debugfs the right thing to use here? Anyone? Please enlighten.
>>
>> _Leo
>>
>
>
> After some analysis, I have decided to use netlink sockets for my use case.
> Some queries regarding the same:
>
> 1. Are netlink sockets an overkill for not so heavy data transfer ?
> 2. Do I have to recompile kernel etc for loading my module which usages
> netlink sockets?
> 3. Are they widely available everywhere? Meaning 2.4 and 2.6 kernles as
> well?
> 4. Any idea whether these are available on BSD kernel as well? I think they
> are.
>
nail...using signal to announce make more sense in my opinion.
>
> _Leo
>
>
>
True, netlink is good but may be not in my case, I am getting in a subset of networking subsytem
to my job which can be done in a more light weight manner using mmap + signals. I guess i am going
with mmap + signal approach.
Thanks all for the inputs.
-Leo.
