January 2012 - kernelnewbies@kernelnewbies.org

some questions about log level
by loody June 29, 2012

June 29, 2012

hi all: my questions are below: 1. Can I temporarily let kernel message show in stdout? I google some key word as "console_loglevel" and I found following methods: a. echo 8 > /proc/sys/kernel/printk b. write a simple program which calling "klogctl(8, NULL, level)" Then I purposely connect/disconnect USB, but my console keep quiet. But dmesg shows connect/disconnect messages. 2. what is differences between above a and b methods? Are they not to used to change console_loglevel? 3. is it possible the max level of "console_loglevel" doesn't mean it will show on stdout? -- Thanks for your help

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Need help: Generating patch using git
by amit mehta March 8, 2012

March 8, 2012

Hi, kernel janitors group seem like a good place to start learning linux kernel and after reading some of the information available on kernel newbies website, i tried to generate a dummy patch and need your help for moving in correct direction of learning and contributing to linux kernel. So these are the steps that i've followed to generate this dummy patch. 1: Download the latest linux kernel sources using git # mkdir linux-next # cd linux-next # git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git linux-2.6 2: Do some modifications. # pwd /root/linux-next/linux-2.6 # git diff diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c index 6e412a6..9858701 100644 --- a/net/ipv4/ipconfig.c +++ b/net/ipv4/ipconfig.c @@ -441,7 +441,7 @@ static int __init ic_defaults(void) &ic_myaddr); return -1; } - printk("IP-Config: Guessing netmask %pI4\n", &ic_netmask); + printk(KERN_INFO "IP-Config: Guessing netmask %pI4\n", &ic_netmask); } return 0; 3: Generate a patch # pwd /root/linux-next/linux-2.6 # mkdir ../patches # git diff >../patches/ipconfigPatch.txt 4: Test your patch 4a: Clear the local changes from the tree # git checkout -f 4b: Apply the patch # git apply ../patches/ipconfigPatch.txt The above step(4b) did not returned any git error so it seems to me that the steps to generate this patch was correct. 5: Check your mailer 5a: I just copied the contents of ../patches/ipconfigPatch.txt and pasted in the compose area and sent that mail to myself. After receiving this mail i copied and pasted the mail contents in a file under /root/linux-next/patches/dummyPatch.txt and tried to apply this patch using git but it gave me an error as below: # git apply ../patches/dummy.txt fatal: corrupt patch at line 11 Hence it seems i'm missing something here. Please note that this is just for my understanding purpose of generating and submitting patches. -Amit

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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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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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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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Diff. between CPU Hard-lockup and Soft-lockup
by devendra rawat Jan. 31, 2012

Jan. 31, 2012

Hi, What are the Differences between CPU Hard-lockup and Soft-lockup. Regards, Devendra

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Re: kernel swap accounting...
by Vladimir Murzin Jan. 31, 2012

Jan. 31, 2012

Hi! AFAIK, shared pages usually get in swap cache first and stay there till page reference count reaches limit. As soon as it is reached page is swapped out on disk. P.S. Sorry for posting reply over original message. E-mail client on my handheld device isn't configurable enough :-( ------Original Message------ From: Mulyadi Santosa Sender: kernelnewbies-bounces(a)kernelnewbies.org To: kernelnewbies Subject: kernel swap accounting... Sent: 31 Jan 2012 18:02 Hi all Recently I dig out my old script that count the total number of swapped out pages. Basically, the script looks like this (sorry for any obvious typo): for a in /proc/[0-9]* do strings $a/cmdline; echo ; grep Swap $a/smaps | awk '{ SUM += $2 } END { print SUM }'; echo ----------------; done the problem is: the total number of swapped out pages (in kilobytes) doesn't match the output of "free" (swap used column). The difference is not really big, it ranges around 1-2 megabytes in my measurements. Anybody knows why? -- 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 Best wishes, Vladimir Murzin

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kernel swap accounting...
by Mulyadi Santosa Jan. 31, 2012

Jan. 31, 2012

Hi all Recently I dig out my old script that count the total number of swapped out pages. Basically, the script looks like this (sorry for any obvious typo): for a in /proc/[0-9]* do strings $a/cmdline; echo ; grep Swap $a/smaps | awk '{ SUM += $2 } END { print SUM }'; echo ----------------; done the problem is: the total number of swapped out pages (in kilobytes) doesn't match the output of "free" (swap used column). The difference is not really big, it ranges around 1-2 megabytes in my measurements. Anybody knows why? -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com

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Data Recovery
by Swapnil Gaikwad Jan. 31, 2012

Jan. 31, 2012

Hi, I have a Hp laptop with i5 Processor, 640 GB HD. My HD is Crashed due to damage. It does not have any partition table in it. Then how I can recover my data from it. Is anybody have some tool that to it? (Note : Recover My File software showed some files in it, But it requires license key. ) -- Regards, Swapnil Gaikwad.

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Re: Using tasklist_lock in a module -- is there an alternative?
by Arokux B. Jan. 31, 2012

Jan. 31, 2012

On Tue, Jan 31, 2012 at 4:39 AM, Pei Lin <telent997(a)gmail.com> wrote: > 2012/1/30 Arokux B. <arokux(a)gmail.com>: >> Hi, >> >> For learning purposes I would like to iterate through all the >> processes in a module and output different information about them. For > What information did you want to get for processes? /proc/PID/xxx is > not enough for u? >> this task I need to lock the list of all tasks. I've seen some example >> in the kernel code which lock tasklist_lock. However this symbol > tasklist_lock had been deprecated for a long time. Maybe rcu_read_lock > could help u. >> cannot be used by modules. Is there any other way I can lock the list >> of tasks then? >> >> Thanks >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies(a)kernelnewbies.org >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > > > -- > Best Regards > Lin Hi, thank you for your reply. It would be enough, however I want to do some kernel programming. Regards, Roman

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