April 2012 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Netlabel
by Christophe Hauser April 26, 2012

April 26, 2012

Hi all, is anyone here familiar with Netlabel ? I am trying to label network packets using CIPSO tags from a LSM module. Rather than using the Netlink interface to configure Netlabel from userspace, I try to setup everything from kernelspace. The way I initialize netlabel is similar to what smack does in smk_cipso_doi() (security/smack/smackfs.c). What I am trying to do is the following : - no packet should ever get dropped - unlabeled packets can stay unlabeled, I don't need to assign them any DOI - labeled packets carry information that is only useful to my LSM module (bitmaps) Now, everytime I label a socket, packets get dropped. I read in the RFC about configuration settings such as HOST_LABEL_MAX and so on, but as far as I understand, it is up to the module itself to make such verifications. Is netlabel enforcing any sort of policy here ? Is there anyway I can configure netlabel to never drop packets ? Kind regards, -- Christophe

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freelance kernel work
by Christopher Harvey April 26, 2012

April 26, 2012

I'm not looking for work, nor do I have any work for others. I'm just curious if there is a central location where freelance kernel developers hang out. I've never seen any email on mailing lists like "I have some hardware and want somebody to write a kernel module for it". I thought that sort of request would have been common.

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Linux Driver Project
by Rabee Al-Maqabi April 26, 2012

April 26, 2012

Hi, I am looking for not yet supported piece of hardware to write a driver for it. anyone can help? Regards, Rabee Al-Maqabi

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Profiling my Modules
by Rishi Agrawal April 26, 2012

April 26, 2012

Hi All, I have a kernel module which has functions which take a lot of time in execution. I am curious to know how can I profile it, and find out the functions taking most of the time. I saw Oprofile, but it seems that I will have to build the whole kernel, and also that it will be difficult to profile my module through it. Any trick or tool will do. -- Regards, Rishi Agrawal

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Re: side effects of calling interruptible_sleep_on_timeout()
by Arun KS April 26, 2012

April 26, 2012

On Thu, Apr 26, 2012 at 3:48 PM, Shashidhara Shamaiah <Shashidhara.Shamaiah(a)mphasis.com> wrote: > Hi Arun, > > My question is how will the scheduler run, if interrupts are disabled on the local CPU. As timer interrupt controls the CPU? scheduler is nothing but a piece of code( __schedule()) which is just like any other function. If interrupts are disabled, you wont be getting the timer interrupts. So time slice will never get elapsed, which in turn allows current process to run for ever until it calls schedule again or exits. But as we figured out that __scheduler is enabling the interrupts back before we really schedules out. So this problem won't occur in our Linux kernel. Thanks, Arun > > Regards > Shashidhara > > -----Original Message----- > From: Arun KS [mailto:getarunks@gmail.com] > Sent: Thursday, April 26, 2012 11:36 AM > To: Shashidhara Shamaiah > Subject: Re: side effects of calling interruptible_sleep_on_timeout() > > Hi, > > My code is, > > /* disable interrupts and preemption */ > spin_lock_irqsave(&lock, flags); > /* enable preemption, but interrupt still disabled */ > spin_unlock(&lock); > /* Now schedule something else */ > schedule_timeout(10 * HZ); > > If you see the second step spin_unlock(&lock). This will enable the > preemtion back. > > Arun > > On Thu, Apr 26, 2012 at 11:26 AM, Shashidhara Shamaiah > <Shashidhara.Shamaiah(a)mphasis.com> wrote: >> Hi Arun, >> >> I think if you run the code on a SMP machine, then the BUG() in schedule() will be triggered as spinlock_irqsave() disables preemption for a SMP. >> >> Regards >> Shashidhara >> >> -----Original Message----- >> From: Arun KS [mailto:getarunks@gmail.com] >> Sent: Thursday, April 26, 2012 10:41 AM >> To: Shashidhara Shamaiah >> Subject: Re: side effects of calling interruptible_sleep_on_timeout() >> >> Hello Shashidhara, >> >> My machine is UP. >> >> thanks, >> Arun >> >> On Thu, Apr 26, 2012 at 10:23 AM, Shashidhara Shamaiah >> <Shashidhara.Shamaiah(a)mphasis.com> wrote: >>> Hi Arun, >>> >>> One more question regarding your experiment. Were you running your code on a UP or SMP machine? >>> >>> Regards >>> Shashidhara >>> >>> -----Original Message----- >>> From: kernelnewbies-bounces(a)kernelnewbies.org [mailto:kernelnewbies-bounces@kernelnewbies.org] On Behalf Of Arun KS >>> Sent: Thursday, April 26, 2012 10:03 AM >>> To: Srivatsa S. Bhat >>> Cc: vinayak menon; Philipp Ittershagen; devendra rawat; kernelnewbies(a)kernelnewbies.org >>> Subject: Re: side effects of calling interruptible_sleep_on_timeout() >>> >>> Hi Srivatsa, >>> >>> On Wed, Apr 25, 2012 at 3:56 PM, Srivatsa S. Bhat >>> <srivatsa.bhat(a)linux.vnet.ibm.com> wrote: >>>> On 04/25/2012 03:36 AM, Philipp Ittershagen wrote: >>>> >>>>> Hi Devendra, >>>>> >>>>> On Tue, Apr 24, 2012 at 03:24:23PM +0530, devendra rawat wrote: >>>>>> Hi, >>>>>> A switch driver is causing soft lockup on Montavista Linux Kernel >>>>>> 2.6.10 system. >>>>>> While browsing through the code of the driver. I came across a snippet >>>>>> where after disabling the interrupts >>>>>> a call is made to interruptible_sleep_on_timeout(). >>>>>> The code snippet is like >>>>>> cli(); >>>>>> init_waitqueue_head(&queue); >>>>>> interruptible_sleep_on_timeout(&queue, USEC_TO_JIFFIES(usec)); >>>>>> thread_check_signals(); >>>>>> sti(); >>>>>> I need to know the side effect of this sort of code, can it be >>>>>> responsible for the softlockup of the system ? Its a PowerPC based >>>>>> system. >>>>> >>>>> you cannot call sleep functions after disabling interrupts, because no >>>>> interrupt will arrive for the scheduler to see the timeout and resume your >>>>> task. >>>>> >>>> >>>> >>>> Yes, that's right. Also, in general, sleeping inside atomic sections (eg., >>>> sections with interrupts disabled or preempt disabled) is wrong. There is a >>>> config option in the kernel that you can use to enable >>>> sleep-inside-atomic-section-checking (CONFIG_DEBUG_ATOMIC_SLEEP I believe), >>>> which can help you pin-point such bugs easily. >>> >>> I tired an experiment to check this. >>> >>> /* disable interrupts and preemption */ >>> spin_lock_irqsave(&lock, flags); >>> /* enable preemption, but interrupt still disabled */ >>> spin_unlock(&lock); >>> /* Now schedule something else */ >>> schedule_timeout(10 * HZ); >>> >>> But this is not causing any harm. I m able to call schedule with >>> interrupt disabled and system works fine afterwards. >>> >>> So when I looked inside the schedule() function, it checks only >>> whether preemption is disabled or not. schedule calls BUG() only if >>> preemption is disabled and not if interrupts are disabled. >>> >>> And AFAIK there is no fuction inside the kernel which tells you that >>> interrupt are disabled. >>> >>> So explantion why system works fine after calling a schedule with >>> interrupt disabled go here, >>> >>> There is a raw_spin_lock_irq(&rq->lock) inside the __schedule() which >>> in turn calls local_irq_disable(). >>> >>> local_irq_disable/enable() functions are not nested. We dont have >>> reference counting. >>> One call to local_irq_enable is enough to enable multiple calls of >>> local_irq_disable(). >>> >>> So my inference is that if you call a schedule with interrupt disable >>> will not cause any problem. Because schedule function enable it back >>> before we really schedules out. >>> But call to schedule() with preemtion disabled will end up in famous >>> BUG scheduling while atomic. >>> >>> NB: Kernel version used is 3.0.15 >>> >>> Thanks, >>> Arun >>> >>> >>>> >>>> Regards, >>>> Srivatsa S. Bhat >>>> >>>> >>>> _______________________________________________ >>>> Kernelnewbies mailing list >>>> Kernelnewbies(a)kernelnewbies.org >>>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >>> >>> _______________________________________________ >>> Kernelnewbies mailing list >>> Kernelnewbies(a)kernelnewbies.org >>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >>> >>> Information transmitted by this e-mail is proprietary to MphasiS, its associated companies and/ or its customers and is intended >>> for use only by the individual or entity to which it is addressed, and may contain information that is privileged, confidential or >>> exempt from disclosure under applicable law. If you are not the intended recipient or it appears that this mail has been forwarded >>> to you without proper authority, you are notified that any use or dissemination of this information in any manner is strictly >>> prohibited. In such cases, please notify us immediately at mailmaster(a)mphasis.com and delete this mail from your records. >>> >> >> Information transmitted by this e-mail is proprietary to MphasiS, its associated companies and/ or its customers and is intended >> for use only by the individual or entity to which it is addressed, and may contain information that is privileged, confidential or >> exempt from disclosure under applicable law. If you are not the intended recipient or it appears that this mail has been forwarded >> to you without proper authority, you are notified that any use or dissemination of this information in any manner is strictly >> prohibited. In such cases, please notify us immediately at mailmaster(a)mphasis.com and delete this mail from your records. >> > > Information transmitted by this e-mail is proprietary to MphasiS, its associated companies and/ or its customers and is intended > for use only by the individual or entity to which it is addressed, and may contain information that is privileged, confidential or > exempt from disclosure under applicable law. If you are not the intended recipient or it appears that this mail has been forwarded > to you without proper authority, you are notified that any use or dissemination of this information in any manner is strictly > prohibited. In such cases, please notify us immediately at mailmaster(a)mphasis.com and delete this mail from your records. >

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Re: [Celinux-dev] [Q] TinyLinux project status (resend)
by Thomas Petazzoni April 26, 2012

April 26, 2012

Le Thu, 26 Apr 2012 20:13:08 +1000, Greg Ungerer <gerg(a)snapgear.com> a écrit : > > I haven't posted it anywhere else because it's a hack to workaround a > > Qemu problem: the 5208 apparently has support for separate supervisor > > and userspace stack pointers (through two different registers), but > > Qemu doesn't emulate that. So I think it's a flaw in Qemu emulation > > rather than a kernel problem, but it was easier for now to workaround > > it by just adding one "select COLDFIRE_SW_A7". > > Ah, ok. I only put the dual stack pointer support in a year or 2 back. > And it is only supported on the more modern ColdFire's, guess the QEMU > support is for the simpler parts :-) Well, either Qemu pretends to emulate a 5208 and it should support the dual stack pointer thing, or it shouldn't pretend to emulate a 5208. Am I correct in my understanding is that the 5208 hardware does support dual stack pointers? Best regards, Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com

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Re: Open to work for any kernel module
by Anuz Pratap Singh Tomar April 26, 2012

April 26, 2012

On Thu, Apr 26, 2012 at 2:18 AM, Anil Varma Biruduraju < anilvarma87(a)gmail.com> wrote: > Hi Anuz, > > Thanks for the reply.. > > I looked at the Kernel janitors web link but dont know > where to start I see coding standards and wondering what to do... > > I know I might me asking a lot but can you please let > to know where to start and whom to contact first.. > > Thank you > > there is a kernel janitor mailing list, also try looking for kernel bugs at kernel bugzilla, you may find something interesting: https://bugzilla.kernel.org > Regards, > Anil Varma B. > > On Mon, Apr 23, 2012 at 4:27 AM, Anuz Pratap Singh Tomar > <chambilkethakur(a)gmail.com> wrote: > > > > > > On Mon, Apr 23, 2012 at 6:12 AM, Anil Varma Biruduraju > > <anilvarma87(a)gmail.com> wrote: > >> > >> Hi All, > >> > >> Please let me know if I can start working on some > >> kernel modules. > >> Thank you. > >> > > Try to look up in kernel janitors. > > >

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side effects of calling interruptible_sleep_on_timeout()
by devendra rawat April 26, 2012

April 26, 2012

Hi, A switch driver is causing soft lockup on Montavista Linux Kernel 2.6.10 system. While browsing through the code of the driver. I came across a snippet where after disabling the interrupts a call is made to interruptible_sleep_on_timeout(). The code snippet is like cli(); init_waitqueue_head(&queue); interruptible_sleep_on_timeout(&queue, USEC_TO_JIFFIES(usec)); thread_check_signals(); sti(); I need to know the side effect of this sort of code, can it be responsible for the softlockup of the system ? Its a PowerPC based system. Regards, Devendra

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Re: [Celinux-dev] [Q] TinyLinux project status (resend)
by Thomas Petazzoni April 26, 2012

April 26, 2012

Hello Greg, Le Thu, 26 Apr 2012 09:56:23 +1000, Greg Ungerer <gerg(a)snapgear.com> a écrit : > I couldn't see any kernel patches linked here. Did you need any, > or have you posted them somewhere else? The kernel patch is at http://lists.busybox.net/pipermail/buildroot/2012-April/052585.html, hidden inside a Buildroot patch. I haven't posted it anywhere else because it's a hack to workaround a Qemu problem: the 5208 apparently has support for separate supervisor and userspace stack pointers (through two different registers), but Qemu doesn't emulate that. So I think it's a flaw in Qemu emulation rather than a kernel problem, but it was easier for now to workaround it by just adding one "select COLDFIRE_SW_A7". > Nice to see that it can run under QEMU! Well, as I said, it actually doesn't run very well: if I use /bin/sh as init=, then I can run *one* command, and the kernel crashes :-) So we can say it boot all the way to userspace, but userspace isn't very useful :) Regards, Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com

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Re: [Celinux-dev] [Q] TinyLinux project status (resend)
by Thomas Petazzoni April 25, 2012

April 25, 2012

Hello, Le Wed, 25 Apr 2012 15:14:09 -0500, Rob Landley <rob(a)landley.net> a écrit : > Query: is there any way to set up a nommu system with: > > A) stock vanilla upstream packages (kernel, uClibc, busybox) > B) running under qemu > > I've had a todo item to add a nommu target to Aboriginal Linux but every > time I do so I poke at making i386 nommu and it just doesn't seem to > want to do that. (Can't imagine why...) With a few Qemu patches and kernel patches, I'm able to boot into userspace a Coldfire system under the Qemu Coldfire emulation. However, the system crashes as soon as the first userspace program exits (the kernel thinks I'm killing init, I haven't had the time to investigate this). The kernel configuration and Qemu patches have been posted at http://lists.busybox.net/pipermail/buildroot/2012-April/052581.html. I have also been able to boot an ARM noMMU kernel for the AT91x40 SoC under SkyEye. This time, the userspace works fine. I haven't had the time to clean up this, and it requires patches to both the kernel and SkyEye to work properly. If you're interested, I'll give you these patches and configs when I'm done with the cleanup. Best regards, Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com

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