February 2012 - kernelnewbies@kernelnewbies.org

Changes in block layer for IOScheduler Insertion selection
by mani Feb. 6, 2012

Feb. 6, 2012

Dear All, I am working on linux kernel 2.6.32.9 tegra NVIDIA board. I am getting ~8MBps speed of the Nand disk if i use hdparm hdparm -t /dev/mtdblock3 i made changes in block layer of kernel as below:- block/blk-core.c static inline void add_request(struct request_queue *q, struct request *req) { drive_stat_acct(req, 1); /* * elevator indicated where it wants this request to be * inserted at elevator_merge time */ __elv_add_request(q, req, ELEVATOR_INSERT_BACK, 0); //__elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0); } changed ELEVATOR_INSERT_SORT to ELEVATOR_INSERT_BACK it improves my NAND speed to 10MBps. I am using "noop" I/O scheduler. Will this change have any adverse effect in kernel ? or any other side effect as far as i am using only Nand no Hard disk. Thanks Mani

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How to create patch for checkpatch.pl cleanups
by kashyap gada Feb. 6, 2012

Feb. 6, 2012

Hello Linux Newbies, I'm one too. I was looking out for some clean up work and I ran the checkpatch.pl script. I came across a file with some 400 errors and 200 warnings. Now there were bunch of 80 char per line warning , braces and related things. I don't want to be sending patches for each and every error or warning I fix as it becomes tedious and If i send lots of correction patches in one go the kernel maintainers wont accept it. I want to know Can we correct all similar errors or warnings in one patch? or series of patches? Kashyap Gada gada.kashyap(a)gmail.com

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How to read and manipulate IP header using Java.
by Prashant Patil Feb. 6, 2012

Feb. 6, 2012

<kernelnewbies(a)kernelnewbies.org> Hello, I am doing a project, titled “Steganography using TCP/IP”. In this project, first we have to encrypt the secret message that sender wants to send for the receiver. After encrypting, embed that cipher data into image file, the output is as a stego image and that stego image we have to store in unused field of ip header. Like, identification field is used only when fragmentation occurs, if we avoid fragmentation then identification field is always be unused, we can store our stego imgae in it. I have completed Encryption and Embedding part, but problem with the IP header. Please suggest how to read IP header using JAVA. Thanks in advance… Regards, Prashant Patil.

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Writing to kernel address space && KWE UWE bits in PTE
by SaNtosh kuLkarni Feb. 4, 2012

Feb. 4, 2012

My doubt is when , in a, say 3:1 partition of kernel user space address space, if a user space application tries to write/access the 1gb portion of kernel space which it cant, is it because there is not page table entry in the user space process page table entry or......... is it because of a PTE ( page table entry) entry related to access control set to KWE and a kernel trap occurs.What events take place when a user land process tries to write to kernel space address. -- *Regards, Santosh Kulkarni*

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Newest kernel appears to break tap feature - good starting point for kernel development?
by Reza Feb. 4, 2012

Feb. 4, 2012

Hi all, I'm interested in getting involved in kernel development. I compiled the latest kernel and found that it broke the tap feature on my asus x54h k54l. I had a look at the way the devices were interpreted and /proc/bus/input/devices gave different results. This seems like it may be a good starting point but I'm not sure where to go from here or whether it's an issue with the kernel. I presume it is as switching back to the older kernel fixes the tapping for left click. Any advice on where to go from here would be greatly appreciated. Thanks. Reza -works fine- Linux laptop 3.1.0-1-amd64 #1 SMP Tue Jan 10 05:01:58 UTC 2012 x86_64 GNU/Linux I: Bus=0011 Vendor=0002 Product=0001 Version=0063 N: Name="PS/2 Logitech Wheel Mouse" P: Phys=isa0060/serio4/input0 S: Sysfs=/devices/platform/i8042/serio4/input/input6 U: Uniq= H: Handlers=mouse0 event6 B: PROP=0 B: EV=7 B: KEY=70000 0 0 0 0 B: REL=103 -latest kernel where the tap feature breaks- Linux laptop 3.3.0-rc2+ #5 SMP Fri Feb 3 21:05:27 GMT 2012 x86_64 GNU/Linux I: Bus=0011 Vendor=0002 Product=000e Version=0000 N: Name="ETPS/2 Elantech Touchpad" P: Phys=isa0060/serio4/input0 S: Sysfs=/devices/platform/i8042/serio4/input/input6 U: Uniq= H: Handlers=mouse0 event6 B: PROP=0 B: EV=b B: KEY=6420 30000 0 0 0 0 B: ABS=260800011000003

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Re: Best way to debug an Intel Core i5 hang - likely graphics (possibly power) related
by Mulyadi Santosa Feb. 3, 2012

Feb. 3, 2012

Hi again :) On Sat, Jan 21, 2012 at 16:58, Graeme Russ <graeme.russ(a)gmail.com> wrote: > Tell me about it :( - I've been here before, just not with the Linux kernel At least I can tell you will get hiccup less :) Anyway, you do have data backup, right? Just in case it causes corrupt and you lose some of your data. Better safe than sorry... > I got netconsole working and it took a while to crash, but it finally did > and guess what - No oops :( Ok, no luck....how about serial console? same result? (I am not sure which one will be helpful in your case). Just crossing my mind, is this bug also happen if you work strictly in text console i.e no X Window at all? > I've added more (see attached config) >From what I can see at a glance, you already enabled enough debugging features....so just keep it that way at least for now. > Also, I am using a very recent tip of linus' branch (commit > ccb19d263fd1c9e34948e2158c53eacbff369344) I think this is the way it will go, you would likely doing bisecting. Thing is, you first need to find kernel version that works well. You said you have trouble with 3.1.9-fc...how about 3.1.8 or below? > Hmmm, any way to test this theory? Let's say, switching cpu governor? What do you use now? ondemand? then try to switch to conservative. Or just lock the cpu frequency into certain number. -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com

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struct sock->inet_sock convert question
by hu jun Feb. 3, 2012

Feb. 3, 2012

in kernel linux-2.6.16.60-0.54.5 code: static int inet_create(struct socket *sock, int protocol){struct sock *sk;struct inet_sock *inet;.... sk = sk_alloc(PF_INET, GFP_KERNEL, answer_prot, 1); if (sk == NULL) goto out; inet = inet_sk(sk);inet->is_icsk = (INET_PROTOSW_ICSK & answer_flags) == INET_PROTOSW_ICSK; if (SOCK_RAW == sock->type) { inet->num = protocol; if (IPPROTO_RAW == protocol) inet->hdrincl = 1; } if (ipv4_config.no_pmtu_disc) inet->pmtudisc = IP_PMTUDISC_DONT; else inet->pmtudisc = IP_PMTUDISC_WANT; inet->id = 0;....} my question is in the red line , why can convert like that? thanks!

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creation of blktrace completion messages
by Matthias Brugger Feb. 2, 2012

Feb. 2, 2012

Hi all, where does the kernel create the blktrace completion messages? Is it done in the interrupt routine or in the block layer. I just found: register_trace_block_rq_complete(blk_add_trace_rq_complete, NULL); and register_trace_block_bio_complete(blk_add_trace_bio_complete, NULL); But I don't find the corresponding functions. Thanks, Matthias --- http://motzblog.wordpress.com/

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kernel helper functions to convert u64 to u8 array
by Prajosh Premdas Feb. 2, 2012

Feb. 2, 2012

Hi Can anybody please tell me, Is there any kernel helper functions to convert u64 to u8 array, etc? Is there any link where i can get a complete list of all the helper functions -- Regards, Prajosh Premdas

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Query regarding Kmemleak
by Smital Desai Feb. 1, 2012

Feb. 1, 2012

Hello , I am just trying to understand Kmemleak support. In a test program , allocating some memory using and vmalloc () and freeing it in exit () routine. But when i run a kmemleak , It reports this as a leak. But isn't it a generic reuirement to allocate something for the lifetime of the module and free when we remove the module. ? Can somebody explain ? I have provided the kmemleak output and my test program below. Thanks, Smital Desai ================================================================================= cat /sys/kernel/debug/memleak unreferenced object 0xe1b18000 (size 512): comm "insmod", pid 1066, jiffies 4294953148 (age 54.630s) hex dump (first 32 bytes): 36 1c 00 00 02 16 00 00 3c 1c 00 00 02 16 00 00 6.......<....... 43 1c 00 00 02 16 00 00 4f 1c 00 00 02 16 00 00 C.......O....... backtrace: [<c0234ecc>] __vmalloc_node_range+0x1a8/0x1d0 [<c0234f2c>] __vmalloc_node+0x38/0x44 [<c023507c>] vmalloc+0x28/0x30 [<bf00200c>] 0xbf00200c [<c0100458>] do_one_initcall+0x94/0x164 [<c01d639c>] sys_init_module+0x70/0x190 [<c0105d60>] ret_fast_syscall+0x0/0x30 [<ffffffff>] 0xffffffff unreferenced object 0xe1b1a000 (size 512): comm "insmod", pid 1066, jiffies 4294953148 (age 54.630s) hex dump (first 32 bytes): 00 00 00 00 00 2c 00 00 00 00 00 00 2a 03 00 00 .....,......*... 00 00 00 00 00 2c 00 00 bc 00 00 00 02 2e 00 00 .....,.......... backtrace: [<c0234ecc>] __vmalloc_node_range+0x1a8/0x1d0 [<c0234f2c>] __vmalloc_node+0x38/0x44 [<c023507c>] vmalloc+0x28/0x30 [<bf00201c>] 0xbf00201c [<c0100458>] do_one_initcall+0x94/0x164 [<c01d639c>] sys_init_module+0x70/0x190 [<c0105d60>] ret_fast_syscall+0x0/0x30 [<ffffffff>] 0xffffffff ===================================================================================== "test.c" ================================================================================== #include <linux/init.h> #include <linux/kernel.h> #include <linux/module.h> #include <linux/kmemleak.h> char *ptr1, *ptr2; /* * Some very simple testing. This function needs to be extended for * proper testing. */ static int __init kmemleak_test_init(void) { ptr1 = vmalloc(512); ptr2 = vmalloc(512); return 0; } module_init(kmemleak_test_init); static void __exit kmemleak_test_exit(void) { vfree(ptr1); vfree(ptr2); } module_exit(kmemleak_test_exit); MODULE_LICENSE("GPL"); ================================================================================== Thanks and Regard Smital Desai The contents of this e-mail and any attachment(s) may contain confidential or privileged information for the intended recipient(s). Unintended recipients are prohibited from taking action on the basis of information in this e-mail and using or disseminating the information, and must notify the sender and delete it from their system. L&T Infotech will not accept responsibility or liability for the accuracy or completeness of, or the presence of any virus or disabling code in this e-mail"

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