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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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block layer: request unplugging threshold: unplug_thresh
by Kumar amit mehta July 2, 2013

July 2, 2013

Hi, While trying to understand the block layer in Linux, I stumbled upon this request(struct request) unplugging threshold(q->unplug_thresh), which is hardcoded to '4'. So far, my understanding is that there could be explicit request unplugging(e.g. multipath module registering it's unplug_fn and later calling blk_unplug) as well as implicit ones(either due to timeout or read/write request threshold reaching to unplug_thresh. So having, q->unplug_thresh = 4 (ref. blk_queue_make_request), seem like a very small value and even if it's not, then why shouldn't the driver such as RAID framework(dm/md), be allowed to manipulate this threshold value ? -Amit

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Re: File system mount issue
by Grzegorz Dwornicki July 1, 2013

July 1, 2013

Your file system has nodev in fikesystems soo it does not require block device. Try none instead /dev/sda1 1 lip 2013 20:29, "Saket Sinha" <saket.sinha89(a)gmail.com> napisał(a): > As suggested > > now when I do- > mount -t HEPunion /dev/sda1 /mnt/sak > > Now I am getting an error message- > > mount:wrong fs, bad option, bad superblock on /dev/sda1, Missing codepage > or other error. > > Regards, > Saket Sinha > > > > On Mon, Jul 1, 2013 at 11:54 PM, Grzegorz Dwornicki <gd1100(a)gmail.com>wrote: > >> Then use HEPunion with -t switch >> >> Greg >> 1 lip 2013 20:18, "Saket Sinha" <saket.sinha89(a)gmail.com> napisał(a): >> >>> Hi Daniel, >>> >>> It shows >>> nodev HEPunion >>> >>> Regards, >>> Saket Sinha >>> >>> >>> On Mon, Jul 1, 2013 at 11:37 PM, Daniel Baluta <daniel.baluta(a)gmail.com>wrote: >>> >>>> On Mon, Jul 1, 2013 at 8:28 PM, Saket Sinha <saket.sinha89(a)gmail.com> >>>> wrote: >>>> > This is to discuss the problems I am facing with mounting our fs in >>>> > 2.6.18.8 kernel in RHEL5. >>>> > >>>> > I have written the entire fs driver(hepunion) built it and generated >>>> my >>>> > driver excutable file hepunion.ko. >>>> > Now after this hepunion.ko gets generated, I insmod it and then so >>>> lsmod to >>>> > see that it is there. >>>> > >>>> > Now how do I mount it? The man page of mount says >>>> > mount -t filesystem-type dev directory >>>> > >>>> > So I created a mount point directory like /mnt/sak. Now I issue a >>>> command >>>> > mount -t hepunion /dev/sda1 /mnt sak >>>> > >>>> > ERROR: no filesystem of type hepunion >>>> >>>> What does "cat /proc/filesystems" says after you insert your module? >>>> >>>> thanks, >>>> daniel. >>>> >>> >>> >>> _______________________________________________ >>> Kernelnewbies mailing list >>> Kernelnewbies(a)kernelnewbies.org >>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >>> >>> >

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File system mount issue
by Saket Sinha July 1, 2013

July 1, 2013

This is to discuss the problems I am facing with mounting our fs in 2.6.18.8 kernel in RHEL5. I have written the entire fs driver(hepunion) built it and generated my driver excutable file hepunion.ko. Now after this hepunion.ko gets generated, I insmod it and then so lsmod to see that it is there. Now how do I mount it? The man page of mount says mount -t filesystem-type dev directory So I created a mount point directory like /mnt/sak. Now I issue a command mount -t hepunion /dev/sda1 /mnt sak ERROR: no filesystem of type hepunion Kindly help. Regards, Saket Sinha

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neigh_hh_output function
by Varun Sharma July 1, 2013

July 1, 2013

Hi, can anyone briefly help me to understand which value is copy in skb through neigh_hh_output(include/net/neighbour.h) ? I print that value but that is not mac address . I see the hh_len comes from struct hh_cache is 14 .Due to this i think mac_header bulid here .But on exploring i found that mac header build in eth_header function .Now What is value copy in skb through neigh_hh_output function ? Regards Varun

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NFSv4/SUNRPC kernel cache
by SaNtosh kuLkarni July 1, 2013

July 1, 2013

Hi, Can anyone briefly help me understand on how the upcall/downcall/cache management interface (used for kernel and user space daemon communication interface) of SUNRPC (as seen in NFSv4) works exactly. A documenation link would suffice else a brief explanation would be fine. -- *Regards, Santosh*

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