On Mon, Sep 14, 2009 at 4:01 PM, Leonidas . <[email protected]> wrote:
> > > On Mon, Sep 14, 2009 at 3:32 PM, Leonidas . <[email protected]> wrote: > >> >> >> On Mon, Sep 14, 2009 at 3:28 PM, Leonidas . <[email protected]>wrote: >> >>> >>> >>> On Mon, Sep 14, 2009 at 2:46 PM, karunakar rao < >>> [email protected]> 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 . <[email protected]>wrote: >>>> >>>>> >>>>> >>>>> On Mon, Sep 14, 2009 at 2:30 PM, karunakar rao < >>>>> [email protected]> 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 . >>>>>> <[email protected]>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. >>>>> 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. >>>>> >>>>> 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. _Leo
