December 2011 - kernelnewbies@kernelnewbies.org

memory barrier in UP
by subin gangadharan Dec. 13, 2011

Dec. 13, 2011

Hi All, I am reading about the barrier from linux kernel development.In this books, he says "On SMP kernels they are defined only as usual memory barriers.where as on UP kernels they are defined only as a compiler barrier" Does this mean in UP, processor won't reorder the instructions ? Could please give any idea on this. -- With Regards Subin Gangadharan I am not afraid and I am also not afraid of being afraid.

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Fwd: kernel 3.2rc4 hangs if I use allyesconfig
by Jim Cromie Dec. 12, 2011

Dec. 12, 2011

should have gone to list.. ---------- Forwarded message ---------- From: rajaneesh acharya <rajaneeshacharya(a)indiatimes.com> Date: Sat, Dec 10, 2011 at 2:48 AM Subject: Re: kernel 3.2rc4 hangs if I use allyesconfig To: Jim Cromie <jim.cromie(a)gmail.com> Hi Jim, allmodconfig and config borrowed from debian distro works fine Regards Rajaneesh as Srivatsa Bhat bhat pointed out, -rc4 probably has the bug fixed later whereas sufficiently old kernels dont. (before it was introduced) ----- Original Message ----- From: Jim Cromie <jim.cromie(a)gmail.com> To: rajaneesh acharya <rajaneeshacharya(a)indiatimes.com> Sent: Sat, 10 Dec 2011 12:31:32 +0530 (IST) Subject: Re: kernel 3.2rc4 hangs if I use allyesconfig On Fri, Dec 9, 2011 at 11:14 PM, rajaneesh acharya <rajaneeshacharya(a)indiatimes.com> wrote: > Hi Mulyadi, > > Please find the screenshot...There are no debug messages being thrown out... > > Ran this from qemu with command > > qemu-system-x86_64 -kernel /boot/vmlinuz-3.2.0 -initrd initramfs.gz > > > > Regards > Rajaneesh > have you tried allmodconfig, or a config borrowed from a distro build ? > > ----- Original Message ----- > From: Mulyadi Santosa <mulyadi.santosa(a)gmail.com> > To: rajaneesh acharya <rajaneeshacharya(a)indiatimes.com> > Cc: kernelnewbies(a)kernelnewbies.org > Sent: Sat, 10 Dec 2011 10:44:40 +0530 (IST) > Subject: Re: kernel 3.2rc4 hangs if I use allyesconfig > > On 09/12/2011, rajaneesh acharya <rajaneeshacharya(a)indiatimes.com> wrote: >> Hi >> >> I created a kernel using the target as allyesconfig. The machine fails to >> bootup (just hangs with 100% cpu utilization) with message "Booting the >> kernel" >> If I use the config from a distro and create the kernel image, it boots >> fine.. > > Hi Rajanesh > > Could you post at least 20 lines of boot messages up to the time it > hangs? The clue is quite too few IMHO. > > AFAIK, it already passed the decompressing of kernel image, so at > least we know there is little chance kernel image got corrupted. > > -- > regards, > > Mulyadi Santosa > Freelance Linux trainer and consultant > > blog: the-hydra.blogspot.com > training: mulyaditraining.blogspot.com > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies(a)kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >

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Conditional compilation depending on CONFIG_FOOBAR
by contemplating zombie Dec. 12, 2011

Dec. 12, 2011

Hi, I want to conditionally compile some code in module if CONFIG_FOOBAR is defined. How can I add this check to my module's makefile? -Thanks.

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Linux Kernel Version 3.x
by Kaushal Shriyan Dec. 12, 2011

Dec. 12, 2011

Hi, Please help me understand the difference between Linux Kernel 3.x vs Linux Kernel 2.6. And also i have not understood http://www.phoronix.com/scan.php?page=news_item&px=OTUwMg about 2.6.40 meaning 3.0 version. And also help me understand about linux-next and mainline vs stable branch on http://www.kernel.org/ Please help me understand. Regards, Kaushal

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coredump issues in SMP kernel.
by solmac john Dec. 12, 2011

Dec. 12, 2011

Hi All, I found some coredump issues in SMP kernel. Issue:- GDB didn’t show the correct backtrace info of cpu which occurred user fault. I am getting user fault occurred on CPU0 but by default GDB show the normal thread backtrace info of CPU1. can some one guide me is this kernel or gdb issue which patch will solve the issue. Thanks, Akhilesh

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kernel 3.2rc4 hangs if I use allyesconfig
by Srivatsa Bhat Dec. 12, 2011

Dec. 12, 2011

Forgot to cc kernelnewbies mailing list while replying.. On Fri, Dec 9, 2011 at 9:39 PM, rajaneesh acharya < rajaneeshacharya(a)indiatimes.com> wrote: > Hi > > I created a kernel using the target as allyesconfig. The machine fails to > bootup (just hangs with 100% cpu utilization) with message "Booting the > kernel" > If I use the config from a distro and create the kernel image, it boots > fine.. > > Apart from the fact that allyesconfig will create a bulky kernel image > and loads lots of drivers that are not needed, what could be other reasons > why this would fail.. I have 8GB RAM and AMD Quad code.. > > For above testing, I used QEMU command as below > >>qemu-system-x86_64 -kernel /boot/vmlinuz-3.2.0 -initrd test.cpio.gz > > Oh, you have an AMD cpu? There was a regression which prevented Linux from booting on some AMD cpus. And this has been fixed in Linux-3.2-rc5. Please try that version and see if the problem still persists. [The specific patch I am referring to is, "x86: Fix boot failures on older AMD CPU's" See https://lkml.org/lkml/2011/12/9/419] Regards, Srivatsa S. Bhat

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Query about Enhanced Out-Of-Memory handling
by bill4carson Dec. 12, 2011

Dec. 12, 2011

Hi, all Since there is a practical needs for user application with the ability to sense kernel memory use pressure, http://elinux.org/Memory_Management gives some approach on this as below: OOM notification in cgroups mem_notify patches Google cgroup OOM handler Nokia OOM enhancements AFAIK, it seems none of these have been merged into mainline or updated continuously, I'm not so familiar with mm system, so may I ask which known approach is best to work with mainline kernel now? -- I am a slow learner but I will keep trying to fight for my dreams! --bill

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task switching and current pointer implemenation question
by subin gangadharan Dec. 11, 2011

Dec. 11, 2011

Hi Guys, I have a question related to task switching.Basically when user space application switches to kernel (through sys calls), which stack will be used for the user app.Mainly I want to know how the current pointer implementation works. I saw that in arm they are masking the sp with ~(THREAD_SIZE -1) and getting the current thread info and from there its taking the task pointer. So here I am a little confused about the stack pointer since when it switches the kernel it will be supervisory mode,so which sp it's referencing.I know it will be a supervisory stack,but how this stack will be related with the user app. If anybody could give a pointer on this,it would be of great help to me. -- With Regards Subin Gangadharan I am not afraid and I am also not afraid of being afraid.

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Queries about Net-Filter Hooks !!!
by Kesava Srinivas Dec. 11, 2011

Dec. 11, 2011

HI Friends, Trying to Play with Net-Filter Hooks and here are my Queries! 1] While adding a New UDP/IP Header over the received skbuffer from NetFilter Module;need to fill the UDP Check-sum. Please let me know ; if there is any Kernel Function which we can use to do this Job ??? OR Do I need to write our own Function to calculate the Check-sum ??? 2] Once after adding New Headers to the received skbuffer ; am trying to return NF_ACCEPT. My Understanding was that ; the newly expanded skbuffer with added Headers will be again taken my Net-Filter Hooks Module and will deliver back to the net device. rt? OR Was there some thing more that I should do ; to send the new skbuffer to the device ?? Looking forward for the reply !! -Thanks in Advance, VKS

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kernel 3.2rc4 hangs if I use allyesconfig
by rajaneesh acharya Dec. 10, 2011

Dec. 10, 2011

Hi I created a kernel using the target as allyesconfig. The machine fails to bootup (just hangs with 100% cpu utilization) with message "Booting the kernel" If I use the config from a distro and create the kernel image, it boots fine.. Apart from the fact that allyesconfig will create a bulky kernel image and loads lots of drivers that are not needed, what could be other reasons why this would fail.. I have 8GB RAM and AMD Quad code.. For above testing, I used QEMU command as below >>qemu-system-x86_64 -kernel /boot/vmlinuz-3.2.0 -initrd test.cpio.gz Regards Rajaneesh PS: Config file has been created using allyesconfig, hence not attached..

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