January 2011 - kernelnewbies@kernelnewbies.org

question about subsys_initcall sequence
by naveen yadav Jan. 21, 2011

Jan. 21, 2011

Hi all, I am migrating kernel to new target, and it hangs in between, I want to know where it hangs. Since it do lots of subsys_initcall(XXX). So i do not know the sequence where it hangs. is there any way from which i can find the sequence of kernel inbuild INIT execution sequence. Thanks

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Re: Debug Logs
by sugnan prabhu Jan. 20, 2011

Jan. 20, 2011

Hi Mulyadi, Finally after making some study on the dprintk source, i found that it can be enable by setting the config CONFIG_CPU_FREQ_DEBUG http://codemonkey.org.uk/projects/cpufreq/ But the above link say that i need to boot the kernel with cpufreq.debug=7, am not getting how to do that. for time being i have got it working by commenting the condition which checks for this variable in the kernel code. Thanks for your help. On Thu, Jan 20, 2011 at 11:11 AM, Mulyadi Santosa <mulyadi.santosa(a)gmail.com > wrote: > Hi Sugnan :) > > On Thu, Jan 20, 2011 at 12:35, sugnan prabhu <sugnan.prabhu(a)gmail.com> > wrote: > > > > Sorry, what i meant is, am unable to find other logs which are being > print > > using dprint,(ex: in fs/nfs/proc.c) i just wanted to know should i enable > > few flags in the kernel in order to enable those debug messages. > > We follow "not doing top posting" rule here, so please make it as your > habit too :) > > OK, about dprint, I absolutely have no idea. IMHO, you could find out > what dprint() really is e.g whether it is similar to printk or using > other mean such as netlink etc. > > Assuming it's using printk() or similar, find out which facility it > uses...from there...combined with syslog.conf (or syslog alike such as > rsyslog), you should easily parse the output. Enabling flag? maybe, > but I think no need to think about the for now. > > -- > regards, > > Mulyadi Santosa > Freelance Linux trainer and consultant > > blog: the-hydra.blogspot.com > training: mulyaditraining.blogspot.com > -- Thanking You, Sugnan Prabhu S http://sugnanprabhu.blogspot.com/

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Regarding Kernel Project
by ashutosh mishra Jan. 20, 2011

Jan. 20, 2011

hi >i want to devlop a linux project..which is best use in industries.... >i dont hav any idea about where to start...can you provide.....some idea...from where to start... >i hav lot of interest..in linux...device driver...

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Re: Running kmemleak without sysfs support
by Daniel Baluta Jan. 20, 2011

Jan. 20, 2011

On Thu, Jan 20, 2011 at 12:52 PM, Catalin Marinas <catalin.marinas(a)arm.com> wrote: > On Thu, 2011-01-20 at 10:41 +0000, Daniel Baluta wrote: >> Can I make any use of kmemcheck if I don't have sysfs >> kernel support enabled? > > Kmemleak can scan output the memory and report the number of leaked > objects but if you need to get additional information about the leaked > objects (like backtrace), you need debugfs enabled. How is this reporting done? It will appear in dmesg output? > DEBUG_FS doesn't seem to be dependent on SYSFS but I never tried to > enable one without the other (you might be able to mount the DEBUG_FS > somewhere other than /sys/kernel/debug/). I see. I was using 2.6.32 where it seems that debugfs depended on sysfs. Decoupling was done some time later [1]. thanks, Daniel. [1] http://kerneltrap.org/mailarchive/linux-kernel/2010/8/5/4603446

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Running kmemleak without sysfs support
by Daniel Baluta Jan. 20, 2011

Jan. 20, 2011

Hello all, Can I make any use of kmemcheck if I don't have sysfs kernel support enabled? thanks, Daniel.

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Sample of quite well structured question (Fwd: How to create "dev" files in sysfs?)
by Mulyadi Santosa Jan. 20, 2011

Jan. 20, 2011

Guys... I believe it's one of the sample of a question that is well structured. ---------- Forwarded message ---------- From: Arvid Brodin <arvid.brodin(a)enea.com> Date: Wed, Jan 19, 2011 at 20:23 Subject: How to create "dev" files in sysfs? To: kernelnewbies(a)kernelnewbies.org Hello, How do I make my platform device a character device that can be handled by udev? Background: I've written a driver for a very simple platform device (a jumper connected to an input pin on the processor). Today I can read the status of the pin through a driver attribute file in sysfs at: /sys/devices/platform/msel/ As a learning experience I want to get udev to detect this device and create a character device file under /dev for it, that I could read to get the pin status. If I understand correctly, udev looks for files named "dev" in sysfs, which contains the major and minor device numbers which udev use to create the device node. From the kernel code it seems that ((struct platform_device *) my_platform_device)->dev->devt would have to be set to contain the major & minor device numbers when the device is created for a "dev" file to appear, which is not possible in this case since the device is registered in board setup code where it seems wrong to get device numbers by calling call alloc_chrdev_region() (right?). I found a few previous questions about this same problem in these kernelnewbies threads: http://www.mail-archive.com/kernelnewbies@nl.linux.org/msg08461.html http://www.mail-archive.com/kernelnewbies@nl.linux.org/msg06807.html Using that info, and looking at the hpet driver code, I initialised a struct miscdevice and called misc_register(). This gives me a /sys/class/misc/msel_chrdev/ folder with the required dev and uevent files. udev also picks up this and creates the corresponding file in /dev. Is this the correct way to do this? One "device" for the hardware and one or more "devices" for the userland interface(s)? Also, looking at my desktop system, there's one device under /sys/devices/platform that also has "dev" files: /sys/devices/platform/serial8250/tty/ttyS1/dev /sys/devices/platform/serial8250/tty/ttyS2/dev /sys/devices/platform/serial8250/tty/ttyS3/dev I notice that these "dev" files appear as subfolders under the platform device's own folder, and not under /sys/class/. Perhaps this is more correct? The source for 8250 is ~223K in 14 different files so I have not been able to decode how they do this. (Please CC me directly if you respond!) Thanks for reading all this, Arvid Brodin Enea Services Stockholm AB _______________________________________________ Kernelnewbies mailing list Kernelnewbies(a)kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com

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Debug Logs
by sugnan prabhu Jan. 20, 2011

Jan. 20, 2011

Hello all, I am trying to work on the NFS and RPC, i am trying to understand the code, i have enabled the debugging messages of rpc using rpcdebug -m <module> -s all. now i can see that lot of debug can be found in /var/log/messages, i do see that there are lot of other debug messages printed in the nfs using dprint other than there logs, so where can i find those logs, or is there any other way to enable them.

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Accessing on-disk datastructures from a module
by Martin DeMello Jan. 19, 2011

Jan. 19, 2011

I would like to maintain some filesystem metadata as an on-disk datastructure that can be read and written to from within the filesystem module. I know file access from within the kernel is a bad idea; what is the recommended alternative for this? I'm thinking of reserving a bunch of blocks at the start of the partition and accessing them directly - is this the right approach? I'm not too sure how to do that either - I figured the way that ext3 maintains its journal would provide a hint, but I can find no documentation on this, and the code is hard to trace through for this one specific thing. martin

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How to create "dev" files in sysfs?
by Arvid Brodin Jan. 19, 2011

Jan. 19, 2011

Hello, How do I make my platform device a character device that can be handled by udev? Background: I've written a driver for a very simple platform device (a jumper connected to an input pin on the processor). Today I can read the status of the pin through a driver attribute file in sysfs at: /sys/devices/platform/msel/ As a learning experience I want to get udev to detect this device and create a character device file under /dev for it, that I could read to get the pin status. If I understand correctly, udev looks for files named "dev" in sysfs, which contains the major and minor device numbers which udev use to create the device node. From the kernel code it seems that ((struct platform_device *) my_platform_device)->dev->devt would have to be set to contain the major & minor device numbers when the device is created for a "dev" file to appear, which is not possible in this case since the device is registered in board setup code where it seems wrong to get device numbers by calling call alloc_chrdev_region() (right?). I found a few previous questions about this same problem in these kernelnewbies threads: http://www.mail-archive.com/kernelnewbies@nl.linux.org/msg08461.html http://www.mail-archive.com/kernelnewbies@nl.linux.org/msg06807.html Using that info, and looking at the hpet driver code, I initialised a struct miscdevice and called misc_register(). This gives me a /sys/class/misc/msel_chrdev/ folder with the required dev and uevent files. udev also picks up this and creates the corresponding file in /dev. Is this the correct way to do this? One "device" for the hardware and one or more "devices" for the userland interface(s)? Also, looking at my desktop system, there's one device under /sys/devices/platform that also has "dev" files: /sys/devices/platform/serial8250/tty/ttyS1/dev /sys/devices/platform/serial8250/tty/ttyS2/dev /sys/devices/platform/serial8250/tty/ttyS3/dev I notice that these "dev" files appear as subfolders under the platform device's own folder, and not under /sys/class/. Perhaps this is more correct? The source for 8250 is ~223K in 14 different files so I have not been able to decode how they do this. (Please CC me directly if you respond!) Thanks for reading all this, Arvid Brodin Enea Services Stockholm AB

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HT: File Permissions of files in /system/bin at compile time
by Pradeep Kumar Jan. 19, 2011

Jan. 19, 2011

HowTo set file permissions of files in /system/bin at compile time of kernel. example : the command reboot under system/bin has persmissions as lrwxr-xr-x -- reboot Is it done throught setting some Kconfig/config variables?? thanks in Advance Goudagunta Pradeep Kumar,

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