July 2013 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

vmpressure API usage
by Christian Parpart July 9, 2013

July 9, 2013

Hey, I would like to make use of the new vmpressure capabilities from within userspace, and whilest the vmpressure_fd() was really intuitive, I wonder how the new version (as found in git master) is meant to be used, as searching in the web doesn't reveal anything and the API (at least I) do not find intuitive anymore. Has anyone an idea on how to use it, now ? Best regards, Christian Parpart.

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Where are these buffer_xxx macros/fucntion defined?
by Kumar amit mehta July 9, 2013

July 9, 2013

Hi, I see that a lot of FS code is using buffer_invalidate(), buffer_req() etc, but I could not find the definition of these anywhere in the tree. What am i missing? For example, see ext3 code using buffer_invalidate() here[1]. For building cscope and tags database, I invoke the following command from the top of the tree: $ make cscope tags [1] http://lxr.linux.no/#linux+v3.10/fs/ext3/namei.c#L926 Thanks, Amit

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Debugging techniques inside kernel
by manty kuma July 8, 2013

July 8, 2013

I am not completely aware of the debugging techniques and utilizing /proc entries that kernel provides to debug the issues. Could you please point me out to some interesting sources related to debugging or it would be very nice if you could list them here at one place. I found out that recently some interesting CONFIGS that enable some debugging features. For ex : *CONFIG_SLUB_DEBUG_ON, *CONFIG_DMA_API_DEBUG I am just told to use these configs and check. Not sure how to use them effectively. Please share if you are aware of these kind of configs and how to use them. To have them at one place it would be useful for debugging beginners like me. Currently i am facing a memory corruption issue. A very Nasty one which has different call stacks everytime it crashes. Looking at the patterns and Area that is getting corrupted, we are suspecting non-linux components that are illegally writing into the comple DDR(ram). So in this case, is there some particular help that kernel can provide me? Currently i have the complete ram dump. I am analyzing it through opensource crash tool. Cheers, Manty!

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On Robert's Love Linux kernel development 3rd edtion
by TD July 7, 2013

July 7, 2013

Hi, I'm trying to lean linux kernel dev. I bought Robert's love book : "Linux Kernel develpment" This book is based on the linux version 2.6. I can see in the kernel.org site that the latest stable version of ther kernel is 3.9.9. So my question is : what is the most efficient way to learn from this book ? 1) Download the 2.6 version and follow the examples and explanations based from this version 2) Download the 3.9.9 version and try to adapt the examples and explanations of the book. 3) Download both so that I can see the differences. Any other idea or suggestion is very welcomed. Cheers,

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Filesystem and files getting corrupted
by Daniel Hilst Selli July 7, 2013

July 7, 2013

I'm working on an embedded project based on var-som-am35 from TI. [1] I experiencing a lot of corruption from files and even the entire filesystem... is there any guide on how debug filesystems corruption? We already tryied vfat and ext3 fs.. changed media, changed machines... The filesystem runs on mmc card, or on usb flash drive... There is a java aplication running on top of this filesystem, which uses JMS, that is very I/O agressive.. Cheers,

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Re: On Robert's Love Linux kernel development 3rd edtion
by Robert P. J. Day July 7, 2013

July 7, 2013

On Sun, 7 Jul 2013, TD wrote: > Thank you for your quick answers.Following your advices, I'll work > directly from the latest version. > > @rday : If I can contribute to your web page, It would be a real pleasure. it's not hard ... just cross-check everything you read in the book against the latest kernel source, make a note of anything that looks different, and [optionally] see if you can determine when and why it changed. then drop me a note and i'll add it to the page. rday -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================

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local_irq_save vs raw_local_irq_save
by Raj Ravi July 5, 2013

July 5, 2013

Hi, Please let me know the difference between local_irq_save and raw_local_irq_save ? At which situation one should use raw_local_irq_save? Also, I read "flags" is where interrupt state is saved while disabling interrupts in local cpu (for local_irq_save). What EXACTLY this flags contains? What do you mean by interrupt state here? Thanks! Kavi

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Kernel hang
by Prabhunath G July 5, 2013

July 5, 2013

Dear All, I am running a desktop machine in runlevel 1. It silently hangs consistently around 5 min after booting. i.e. it will not throw any logs. How can I get the dump of the kernel logs. Thanks, Prabhu

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Question about NETDEV_REGISTER and NETDEV_UNREGISTER events
by Kevin Wilson July 3, 2013

July 3, 2013

Hello, I am having a machine with two ethernet devices. Is there a way to generate NETDEV_REGISTER or NETDEV_UNREGISTER events, besides rmmod/insmod of the device driver ? As far as I can see from the code, this is the only way that the register_netdevice() method and the unregister_netdev() method can be called: http://lxr.free-electrons.com/source/net/core/dev.c#L5196 regards Kevin

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Marking an SKB as stolen
by Adel Qodmani July 3, 2013

July 3, 2013

Hello everyone, In any Netfilter hook, we return NF_STOLEN to mark that we're handling the packet and we'd be responsible for its fate. My question is, my hook calls several functions on the SKB before knowing if I want to steal it or not so is there a way to just mark the SKB itself as stolen instead of using the hook NF_STOLEN return code? Thanks, Adel

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