April 2013 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Can anyone plz explain me the fields
by Tarun Batra April 4, 2013

April 4, 2013

Can anyone plz explain me the fields skb = kmem_cache_alloc(skbuff_head_cache, gfp_mask & ~_ _GFP_DMA); ... ... ... size = SKB_DATA_ALIGN(size); data = kmalloc(size + sizeof(struct skb_shared_info), gfp_mask); It is the simplified version of skb_alloc().

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Related to Network packet in kernel
by Tarun Batra April 4, 2013

April 4, 2013

Hi All, I was reading "Understanding linux networking Internal" book and the pdf "Network packet capture in Linux kernelspace" on the link https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CDQQ… In the "Understanding linux networking Internal" under topic 9.2.2 it is given that The code that takes care of an input frame is split into two parts: first the driver copies the frame into an input queue accessible by the kernel, and then the kernel processes it (usually passing it to a handler dedicated to the associated protocol such as IP). The first part is executed in interrupt context and can preempt the execution of the second part. Now the query is when the 2nd part is scheduled and in "Network packet capture in Linux kernel space" the packet input flow is described as:- When working in interrupt driven model, the nic registers an interrupt handler; • This interrupt handler will be called when a frame is received; • Typically in the handler, we allocate sk buff by calling dev alloc skb(); • Copies data from nic’s buffer to this struct just created; • nic call generic reception routine netif rx(); • netif rx() put frame in per cpu queue; • if queue is full, drop! • net rx action() decision based on skb->protocol; • This function basically dequeues the frame and delivery a copy for every protocol handler; • ptype all and ptype base queues I want to know when netif rx(); and net rx action() are called? Who call them i mean who schedule them. Please guide. Thanks

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socket MSG_DONTROUTE option on local sockets
by devendra.aaru April 4, 2013

April 4, 2013

Hello, If i use the MSG_DONTROUTE option on a local socket, i mean a tcp socket (AF_INET or AF_INET6) with this option. I know that first of all using the tcp AF_INET or INET6 is a dumb decision instead of using the AF_UNIX family, but i have come to a point where i couldn't change this as this code is legacy. If i use the MSG_DONTROUTE option will that be a performance gain on the sockets that communicate inside the system, not to outside? I am guesssing that routing lookup performs once and then it will never. for every packet there is no routing lookup performed so there wont' be much gain in performance? thanks,

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Re: Kernel generates vmImage instead of zImage
by Onur Cem Çelebi April 4, 2013

April 4, 2013

In addition, it could be useful to examine the whole output of compilation I've attacted. 2013/4/4 Onur Cem Çelebi <occelebi(a)gmail.com> > After i have configured kernel with "make menuconfig", then i fired "make" > command into terminal. I have seen such a video in which somebody did the > same as me but he is able to get zImage. In my case, no luck ! > > > 2013/4/4 Mulyadi Santosa <mulyadi.santosa(a)gmail.com> > >> Hi.... :) >> >> On Wed, Apr 3, 2013 at 4:17 PM, Onur Cem Çelebi <occelebi(a)gmail.com> >> wrote: >> > Image Name: Linux-3.7.0-01377-g1061bd7 >> > Created: Mon Mar 25 15:41:30 2013 >> > Image Type: NIOS II Linux Kernel Image (gzip compressed) >> > Data Size: 1445018 Bytes = 1411.15 kB = 1.38 MB >> > Load Address: c8000000 >> > Entry Point: c8000000 >> > Kernel: arch/nios2/boot/vmImage is ready >> > >> > >> > How to obtain zImage ? Am i missing something ? Any help is greatly >> > appreciated. >> >> Can you explain how did you compile that kernel image? >> >> -- >> regards, >> >> Mulyadi Santosa >> Freelance Linux trainer and consultant >> >> blog: the-hydra.blogspot.com >> training: mulyaditraining.blogspot.com >> > >

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A few questions about the kernel-janitors project.
by Jerry Zhang April 4, 2013

April 4, 2013

After reading so much out-of-date on-line document, which i can not identify, i got several questions regarding the FAQ: http://kernelnewbies.org/MigratingInProgress/FAQ.<http://kernelnewbies.org/MigratingInProgress/FAQ> Q1. Is the kernel-janitors still active and welcomed by mainline kernel. Q2. Does this project only aim to linux-2.x kernel, not any current latest kernel--linux-3.x kernel? Q3. "Be sure to check -mm and -kj trees to see if someone already did that. ". Is it still valid? If yes, where to find the -mm tree(seems replaced by linux-next), http://coderock.org/kj/ is the -kj tree, right? Best Regards, Biao

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[help] kernel oops in function gpio_to_irq
by Mylene Josserand April 3, 2013

April 3, 2013

Hi everyone, I have a problem with gpio functions. My kernel version is 3.8.2 and my SoC is a imX27 on a "home-made" board. First, when I boot, I had only the "Starting kernel..." message. So I rebuild my kernel with CONFIG_DEBUG_KERNEL, CONFIG_DEBUG_LL and CONFIG_EARLY_PRINTK. I have also add the line "earlyprintk=console,UART0,115200" on the bootargs of my Barebox. With that, I can see more messages : [...] Unable to handle kernel NULL pointer dereference at virtual address 0000002c pgd = c0004000 [0000002c] *pgd=00000000 Internal error: Oops: 5 [#1] PREEMPT ARM Modules linked in: CPU: 0 Not tainted (3.8.2+ #4) PC is at __gpio_to_irq+0x1c/0x44 LR is at navocap_baseboard_init+0xd8/0x2c8 pc : [<c01fd194>] lr : [<c04fd468>] psr: 60000053 sp : c7835ef0 ip : 00000079 fp : c05a5628 r10: c04f817c r9 : 00000000 r8 : c05a562c r7 : c7834000 r6 : 00000004 r5 : c05158c4 r4 : c0578844 r3 : 000005ac r2 : c05b0410 r1 : c7834000 r0 : 00000000 Flags: nZCv IRQs on FIQs off Mode SVC_32 ISA ARM Segment kernel Control: 0005317f Table: a0004000 DAC: 00000017 Process swapper (pid: 1, stack limit = 0xc78341b8) Stack: (0xc7835ef0 to 0xc7836000) 5ee0: c05158c4 c04fd468 00000002 10009000 5f00: 10009fff 00000000 00000200 00000000 00000000 00000000 c05158c4 c04fd348 5f20: c0578844 c04f819c c04d23dc c00087f8 00000003 00000003 c04d1b2c c06bd6a0 5f40: 00000000 c0578844 c05158c4 00000004 0000008b c05a562c c0515898 c04f6378 5f60: c05a5620 c04f62a0 00000003 00000003 c04f6378 c00403e0 00000000 00000000 5f80: c03cfee0 00000000 00000000 00000000 00000000 00000000 00000000 c03cfeec 5fa0: 00000000 00000000 c03cfee0 c00093b0 00000000 00000000 00000000 00000000 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000 00100000 000a1000 [<c01fd194>] (__gpio_to_irq+0x1c/0x44) from [<c04fd468>] (navocap_baseboard_init+0xd8/0x2c8) [<c04fd468>] (navocap_baseboard_init+0xd8/0x2c8) from [<c04f819c>] (customize_machine+0x20/0x30) [<c04f819c>] (customize_machine+0x20/0x30) from [<c00087f8>] (do_one_initcall+0x2c/0x168) [<c00087f8>] (do_one_initcall+0x2c/0x168) from [<c04f62a0>] (kernel_init_freeable+0xf4/0x1cc) [<c04f62a0>] (kernel_init_freeable+0xf4/0x1cc) from [<c03cfeec>] (kernel_init+0xc/0x164) [<c03cfeec>] (kernel_init+0xc/0x164) from [<c00093b0>] (ret_from_fork+0x14/0x24) Code: e0433100 e1a0c000 e7920003 e24dd004 (e590302c) ---[ end trace 61bb09c25216d85b ]--- Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b The problem is in the function "gpio_to_irq" in my board init functions (navocap_baseboard_init). To know which lines the opps appears, I have followed this tutorial : https://wiki.ubuntu.com/Kernel/KernelDebuggingTricks Thanks to it, I can notice that the opps appears when I called the "gpio_to_irq" function in : ret = request_irq(gpio_to_irq(IMX_GPIO_NR(2,14)), detect_irq, IRQF_TRIGGER_FALLING, "imx-mmc-detect", data); I have checked in other boards how to use this function and it is configured in the same way. I did see where I have made a mistake. Maybe in my config file where I have missed a configuration option ? How to solve this opps problem ? It would be very great if someone could give me some helps / feedbacks on this problem. Thank you in advance ! Best regards, -- Mylène JOSSERAND Navocap

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Biggest Fake Conference in Computer Science
by newtonhanes＠hushmail.com April 3, 2013

April 3, 2013

We are researchers from different parts of the world and conducted a study on the world’s biggest bogus computer science conference WORLDCOMP ( http://sites.google.com/site/worlddump1 ) organized by Prof. Hamid Arabnia from University of Georgia, USA. We submitted a fake paper to WORLDCOMP 2011 and again (the same paper with a modified title) to WORLDCOMP 2012. This paper had numerous fundamental mistakes. Sample statements from that paper include: (1). Binary logic is fuzzy logic and vice versa (2). Pascal developed fuzzy logic (3). Object oriented languages do not exhibit any polymorphism or inheritance (4). TCP and IP are synonyms and are part of OSI model (5). Distributed systems deal with only one computer (6). Laptop is an example for a super computer (7). Operating system is an example for computer hardware Also, our paper did not express any conceptual meaning. However, it was accepted both the times without any modifications (and without any reviews) and we were invited to submit the final paper and a payment of $500+ fee to present the paper. We decided to use the fee for better purposes than making Prof. Hamid Arabnia (Chairman of WORLDCOMP) rich. After that, we received few reminders from WORLDCOMP to pay the fee but we never responded. We MUST say that you should look at the above website if you have any thoughts to submit a paper to WORLDCOMP. DBLP and other indexing agencies have stopped indexing WORLDCOMP’s proceedings since 2011 due to its fakeness. See http://www.informatik.uni-trier.de/~ley/db/conf/icai/index.html for of one of the conferences of WORLDCOMP and notice that there is no listing after 2010. See http://sites.google.com/site/dumpconf for comments from well-known researchers about WORLDCOMP. The status of your WORLDCOMP papers can be changed from “scientific” to “other” (i.e., junk or non-technical) at any time. See the comments http://www.mail-archive.com/tccc@lists.cs.columbia.edu/msg05168.html of a respected researcher on this. Better not to have a paper than having it in WORLDCOMP and spoil the resume and peace of mind forever! Our study revealed that WORLDCOMP is a money making business, using University of Georgia mask, for Prof. Hamid Arabnia. He is throwing out a small chunk of that money (around 20 dollars per paper published in WORLDCOMP’s proceedings) to his puppet (Mr. Ashu Solo or A.M.G. Solo) who publicizes WORLDCOMP and also defends it at various forums, using fake/anonymous names. The puppet uses fake names and defames other conferences to divert traffic to WORLDCOMP. That is, the puppet does all his best to get a maximum number of papers published at WORLDCOMP to get more money into his (and Prof. Hamid Arabnia’s) pockets. Monte Carlo Resort (the venue of WORLDCOMP until 2012) has refused to provide the venue for WORLDCOMP’13 because of the fears of their image being tarnished due to WORLDCOMP’s fraudulent activities. WORLDCOMP’13 will be held at a different resort. WORLDCOMP will not be held after 2013. The paper submission deadline for WORLDCOMP’13 was March 18 and it is extended to April 6 (it will be extended many times, as usual) but still there are no committee members, no reviewers, and there is no conference Chairman. The only contact details available on WORLDCOMP’s website is just an email address! What bothers us the most is that Prof. Hamid Arabnia never posted an apology for the damage he has done to the research community. He is still trying to defend WORLDCOMP. Let us make a direct request to him: publish all reviews for all the papers (after blocking identifiable details) since 2000 conference. Reveal the names and affiliations of all the reviewers (for each year) and how many papers each reviewer had reviewed on average. We also request him to look at the Open Challenge at http://sites.google.com/site/dumpconf Sorry for posting to multiple lists. Spreading the word is the only way to stop this bogus conference. Please forward this message to other mailing lists and people. We are shocked with Prof. Hamid Arabnia and his puppet’s activities http://worldcomp-fake-bogus.blogspot.com Search Google using the keyword worldcomp fake for additional links.

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Method to calculate user space thread size
by naveen yadav April 3, 2013

April 3, 2013

Dear All, I have very complex user space application contain more then 400 threads. I want to limit the stack size in user space, for this I want to know how much stack size each thread use in worst case. To calculate this is I need to modify in kernel ? or current kernel have any support ? or is there a method I can get from smaps? Thanks

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block level cow operation
by Prashant Shah April 3, 2013

April 3, 2013

Hi, I am trying to implement copy on write operation by reading the original disk block and writing it to some other location and then allowing the write to pass though (block the write operation till the read completes) I tried using submit_bio() / sb_bread() to read the block and using the completion API to signal the end of reading the block but the performance of this is very bad. It takes around 12 times more time for any disk writes. Is there any better way to improve the performance ? Not waiting for the completion of the read operation and letting the disk write go through gives good performance but under 10% of the cases the read happens after the write and ends up the the new data and not the original data. Regards.

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sample network driver
by Tarun Batra April 3, 2013

April 3, 2013

Hello All, Does anyone any sample network driver that receives the packet from the network through ip_recv(). If someone knows some link please share. Thanks

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