December 2011 - kernelnewbies@kernelnewbies.org

Re: Debugging memory allocation crash
by Mulyadi Santosa Dec. 30, 2011

Dec. 30, 2011

On Fri, Dec 30, 2011 at 03:11, contemplating zombie <contemplatingzombie(a)gmail.com> wrote: > You were right that it was a problem with freeing memory. At one place > I was freeing memory from (ptr+2) instead of (ptr). OK great! :) it's nice to know you solved your problem. Two heads solving the problem sometimes better than just one, right? :) -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com

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What is Big Kernel Lock?
by sandeep kumar Dec. 29, 2011

Dec. 29, 2011

Hi All, Can any one tell me the significance of BKL? -- With regards, Sandeep Kumar Anantapalli,

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struct net_device locking
by michi1＠michaelblizek.twilightparadox.com Dec. 29, 2011

Dec. 29, 2011

Hi! I could not see any locking being done with "struct net_device" at all even tough there are many read+write accesses to non-atomic variables. For example: Changing mac addresses: user space netlink socket call to set IFLA_ADDRESS http://lxr.linux.no/linux+v3.1.6/net/core/rtnetlink.c#L1521 http://lxr.linux.no/linux+v3.1.6/net/core/rtnetlink.c#L1322 call to device, e.g. http://lxr.linux.no/linux+v3.1.6/drivers/net/e100.c#L2195 Sending an arp response: http://lxr.linux.no/linux+v3.1.6/net/ipv4/arp.c#L859 Any ideas/pointers? -Michi -- programing a layer 3+4 network protocol for mesh networks see http://michaelblizek.twilightparadox.com

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Debugging memory allocation crash
by contemplating zombie Dec. 29, 2011

Dec. 29, 2011

Hi, I have written a kernel module that does frequent memory allocs, reallocs and deallocs. The code randomly crashes at one of the two memory allocation parts - either in krealloc() or in kmem_cache_alloc_notrace (called by kmalloc()). However, when I analyzed both the crash points instructions using gdb, they both turned out to be at the same location in slab_alloc(). I have tried to debug by carefully inspecting the trace dump and my code. However, I am not able identify the problem. All that I get in the trace dump is "general protection fault: 0000 [#1] SMP". There is one more of this message and then the machine just hangs and I have to reboot it (I think any 3 successive general protection faults requires a reboot). Is there some way that I can debug this problem? -ctmzb

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what is trace_sched_kthread_stop_ret used for?
by loody Dec. 29, 2011

Dec. 29, 2011

Dear all: i saw there is a function called "trace_sched_kthread_stop_ret" in some place of kernel. but I found it is empty function. http://lxr.linux.no/linux+v3.1.5/+code=trace_sched_kthread_stop_ret if it is empty, why we still keep it in kernel? -- Regards,

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Re: Kernelnewbies Digest, Vol 13, Issue 42
by venu Dec. 29, 2011

Dec. 29, 2011

AFAIK, BKL is no more useful. p.s. http://www.internetnews.com/skerner/2010/11/linux-2637-kills-the-big-kerne.… so, you can ignore it. However, if you are interested to know its details, go thro' http://lwn.net/Articles/86859/ Date: Thu, 29 Dec 2011 14:33:42 +0530 From: sandeep kumar <coolsandyforyou(a)gmail.com> Subject: What is Big Kernel Lock? To: kernelnewbies(a)kernelnewbies.org Message-ID: <CAL7WMDdSFA37iOgqo8LC%2BJLM05uMK-VhNkxPdUqDiCjKCypdiQ(a)mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" Hi All, Can any one tell me the significance of BKL? -- With regards, Sandeep Kumar Anantapalli,

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Re: ipip6_tunnel_xmit
by Rahul Kumar Dec. 29, 2011

Dec. 29, 2011

Hi, I'm trying to understand the sit driver code net/ipv6/sit.c (2.6.35.12). I'm trying to forward incoming packet from another interface (eth0) to ISATAP tunnel interface (is0) by calling dev_queue_xmit (dev) with dev set to is0. Eventually ipip6_tunnel_xmit routine is getting called, skb_dst()->neighbor is returning null. (I think this is returning null since the dest ip(v6) is incorrectly set). I would like to know what should be the header fields that needs to be set when passing down to tunnel, in order to forward it to isatap router. Please let me know

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Re: Issue with ioctl commands - Linux version 2.6.35.7+
by Chetan Nanda Dec. 29, 2011

Dec. 29, 2011

On Wed, Dec 28, 2011 at 8:22 PM, autif khan <autif.mlist(a)gmail.com> wrote: > Hi Chetan, > > I was wondering if switching to unlocked_ioctl() fixed the issue. > > I will be developing a hardware driver and would like to know how you > made out. Please let me know if the 'cmd' is passed correctly. > > Thanks for sharing. > > Autif > Hi Autif, Please go through the link: http://lwn.net/Articles/119652/ Problem with my dummy driver was that i am using unlocked_ioctl, but defined the ioctl function with wrong syntax (i.e. with syntax of normal ioctl function.) Thanks, Chetan Nanda > > On Tue, Dec 27, 2011 at 10:34 PM, Chetan Nanda <chetannanda(a)gmail.com> > wrote: > > > > > > On Tue, Dec 27, 2011 at 11:25 PM, Dave Hylands <dhylands(a)gmail.com> > wrote: > >> > >> Hi Chetan, > >> > >> On Tue, Dec 27, 2011 at 3:39 AM, Chetan Nanda <chetannanda(a)gmail.com> > >> wrote: > >> > Hi All, > >> > > >> > I am facing a strange issue with the ioctl commands, and not able to > >> > find > >> > what wrong I am doing. > >> > I am trying with a dummy kernel driver and implemented ioctl command > as > >> > follow: > >> > > >> > in my_ioctl.h > >> > #define READHWREG_MAGIC_NUMBER 0x15 > >> > #define READHWREG_CAM_READPE _IOR(READHWREG_MAGIC_NUMBER, 1, int*) > >> > > >> > But the value of 'READHWREG_CAM_READPE' is comes out to be different > in > >> > userspace (in the application) and kernel space (in the driver). > >> > > >> > In userspace I used ioctl as > >> > ... > >> > printf("\ncommand %x \n",READHWREG_CAM_READPE); <-- command > 80041501 > >> > error = ioctl(g_DevFileId, READHWREG_CAM_READPE); > >> > .. > >> > > >> > In kernel space > >> > > >> > int readHwReg_ioctl(struct inode *node, struct file *filp, unsigned > int > >> > cmd, unsigned long arg) > >> > { > >> > ... > >> > printk("\n%d %s cmd = %x\n",__LINE__,__FUNCTION__,cmd); <--- cmd = > >> > bee6a9d4 > >> > >> Back in 2.6.36, the ioctl member of the struct file_operations > >> structure (which took 4 arguments) was finally deprecated, replaced > >> with unlocked_ioctl (which only takes 3 arguments). > >> > >> If you just renamed and ignored the compiler warnings, then that > >> explains your problem. > >> > > Thanks Dave for pointing out 'unlocked_ioctl' > > I come across this link: > > http://lwn.net/Articles/119652/ > > > >> -- > >> Dave Hylands > >> Shuswap, BC, Canada > >> http://www.davehylands.com > > > > > > Thanks, > > Chetan Nanda > > > > _______________________________________________ > > Kernelnewbies mailing list > > Kernelnewbies(a)kernelnewbies.org > > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > >

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how to determine whether in irq context
by loody Dec. 28, 2011

Dec. 28, 2011

Dear all: i remember there is a marco for us to determine whether we are located in irq context. I forget what it is. Would anyone know what it is? -- Thanks for your help

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Re: Strange kernel reboot (oops?)
by Mulyadi Santosa Dec. 28, 2011

Dec. 28, 2011

Hi :) 2011/12/27 Ezequiel García <elezegarcia(a)yahoo.com.ar>: > We've solved the bug that originated this in first place, > so... never mind :) It was strange indeed... > > Thanks anyway for you help. > > Embedded-land is a strange world to live in. Wow nice :) Anyway, mind to share a bit, what was the solution? if it is not top secret :) -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com

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