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Generic question
by Vipul Jain Dec. 7, 2013

Dec. 7, 2013

Hi All, A quick question: If any of user space process is hanged or not responding, does it means kernel is also hung in some part? I trying to understand why hang happens and what triggers it.happening ? How to go about recover a hang process, apart from restarting it. Regards, Vipul.

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Compiling SMBFS module in 3.10 kernel
by Roheen Malu Dec. 6, 2013

Dec. 6, 2013

Hi, I have an old system with kernel version 2.4 and I need to set up a SMB share with another system running 3.10. Can anyone help me to compile a SMBFS kernel module in kernel version 3.10. I checked online and it only has CIFS and found that SMBFS is deprecated. Is CIFS backward compatible with SMBFS or do I need to compile SMBFS separately in the new kernel version. Thanks and regards, Roheen

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How can I 'getchar()' in module code?
by 乃宏周 Dec. 6, 2013

Dec. 6, 2013

For debugging purpose, I want something like 'getchar()' that can pause execution in the module code. Do any candidates I can choose?

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Re: Make File error
by Sudip Mukherjee Dec. 5, 2013

Dec. 5, 2013

> Whats the error? >>>>> >>>> Hi Anil >> Please do not top post. >> For your error , please verify if >> /lib/modules/2.6.32-220.el6.x86_64/build is really linking to the folder >> containing the kernel files. >> >> Regards >> Sudip >> >> > Thats the issue the link is not there how to create the link. > On your mails please always put cc to the list. Even if it is centos the build file will be there. And it should have a soft link to the folder containing your kernel source files. first please find out where your source file is . In my system it is at /usr/src/kernels/<version> In your it should be /usr/src/kernels/2.6.32-220.el6.x86_64 After you find the folder , give the command "sudo ln -s /usr/src/kernels/ 2.6.32-220.el6.x86_64 /lib/modules/2.6.32-220.el6.x86_64/build" Regards Sudip

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Should I pass user-space buffer pointer to read() of struct file implemented by `filp_open()`?
by 乃宏周 Dec. 5, 2013

Dec. 5, 2013

In module code: *unsigned char buf[20];* *struct file *device;* *device = filp_open(...);* *device->f_op->read(device,buf,20,&device->f_pos);* In signature(interface) of *read()* of *struct file*, *buf* should came from user-space. I fed my buffer, and I get correct data from that, Is that correct? Shouldn't I provide a user-space buffer to that ?

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about cheating upper layers
by Guibin(Bill) Tian Dec. 5, 2013

Dec. 5, 2013

Hi there, Right now, I am trying to do such a thing. If a computer has multiple interface A and B, assume the packet is from device A. At ip layer, before the packet is transmitted to transport layer, I change the source address and destination address of the IP header and transmit to transport layer to pretend that this packet is from device B. Not sure whether this can work or not. There are other interface specific information in the skb structure like the net_device member. If I pass the packet to transport layer only with my proposed modification, will the application's socket detect this? I didn't look into the socket match code, not sure if the socket match will check other information in skb struct beside the ip address and port number. Thanks for your help. Bill

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Recovering Linux system from hung state via software
by Vipul Jain Dec. 5, 2013

Dec. 5, 2013

Hi Kernel alias, I am a newbie and I am trying to figure out ways where in I can recover the Linux in below two scenarios: 1. my specific process hangs. 2. kernel gets hung partially or completely. I have done some reading and seems like there is softlockup and hardlockup mechanisms in Linux source base that I can use but not sure, if yes I have below questions: 1. Which kernel version is minimum required for this? 2. How do I know that soft and hard lockup are enabled in my kernel? 3. How can I customize the behavior of default action that been taken? 4. Can I use these two lockup mechanism to find out if my process is hung or not? 5. Any pointers to any docs that can help will be appreciated. I will greatly appreciate any help here. Regards, Vipul.

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watchdog pet in kernel module
by Vipul Jain Dec. 5, 2013

Dec. 5, 2013

Hi, I would like to move the hardware watchdog pet code from user space to kernel space inside the ipmi module and would like to know how to go about pet the hardware watchdog at periodic interval. Any pointers help will be really appreciated. Regards, Vipul.

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Re: How to test my patches for the (staging) android driver?
by Matthias Beyer Dec. 4, 2013

Dec. 4, 2013

Hi kernelnewbies! As I do not get any answer from the other MLs, this goes here, too. Maybe there is just too much noise in lkml... never mind! On 03-12-2013 16:57:08, Matthias Beyer wrote: > Hi, > > Greg-KHs email bot tells me to send this message to a ML. It suggests > to send it to this list or kernelnewbies(a)nl.linux.org, but the latter > results in a failure notice. So I send this email to this list. > > On 03-12-2013 16:16:42, Matthias Beyer wrote: > > Hi, > > > > First: I'm really new to the kernel in manner of submitting patches, > > testing etc. Please, if you send me guidelines or pointers on > > what to do, explain how to do things! > > > > I'm working on some cleanup patches for code in drivers/staging/android/. > > These patches are cleanup patches as suggested in the appropriate TODO > > file, including fixes for checkpatch, but also function splitting as > > there are some really long functions (mainly in binder.c). > > > > How to test my code beside compiling it? Do I even have a possibility > > to test it or should I just send it to you? > > > > Besides: Which ML should I post this (and the patches) to? Main Kernel > > ML? > > > -- Mit freundlichen Grüßen, Kind regards, Matthias Beyer Proudly sent with mutt. Happily signed with gnupg.

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Re: module vs main kernel
by Mulyadi Santosa Dec. 4, 2013

Dec. 4, 2013

On Wed, Dec 4, 2013 at 3:19 AM, Abu Rasheda <rcpilot2010(a)gmail.com> wrote: > On Mon, Dec 2, 2013 at 11:31 PM, Mulyadi Santosa > <mulyadi.santosa(a)gmail.com> wrote: >> On Tue, Dec 3, 2013 at 8:33 AM, Abu Rasheda <rcpilot2010(a)gmail.com> wrote: >>> I have my implementation of socket APIs, >>> >>> I sock_unregister(AF_INET); & sock_register(&inet_family_ops), this replaces >>> kernel resident socket related calls with my socket related calls. My code >>> is loaded as kernel module. >>> >>> My question, is Linux kernel able to call its own socket call more >>> efficiently (less overhead, fewer CPU cycles) than mine ? code is running on >>> Intel x86_64 arch. >>> >>> Any pointer is appreciated. >> >> >> IMHO, strictly from module vs core kernel code perspective, there is >> no speed difference. >> >> The reason is, once the kernel is loaded, it is the kernel itself. So >> it is not separated into isolated segment or something like that. Yes >> module is loaded into vmalloc-ed memory area, but that's it. > > Is it possible that since my code of socket API is located in > different part of memory, so that it needs to make a long jump > (results in d-cache miss) ? > > here is statistics: from per stats tool: > > Linux code: > 112,880,163,053 instructions:HG # 0.72 insns per cycle > > My code: > 32,074,097,170 instructions:HG # 0.34 insns per cycle Hi... please Cc: to kernelnewbies as well. as for d-cache miss, I think that's not due to long jump, but accessing something not cache aligned. Or maybe you can think something that can be prefetched. That way, you utilize the processor pipeline better, but use it wisely -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com

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