February 2012 - kernelnewbies@kernelnewbies.org

Re: 答复: parent inode from the current struct inode
by Jack David Feb. 8, 2012

Feb. 8, 2012

2012/2/8 Tom Lai(IT) <tomlai(a)utstar.com>: > Hi Philipp, > > I checked 2.6.32 that dentry struct contained parent dentry struct. > > > Hi Jack, > > On Wed, Feb 8, 2012 at 8:48 AM, Jack David <jd6589(a)gmail.com> wrote: >> Hi All, >> >> Is possible to get parent directory's inode structure from the current >> inode? If so, how can I do that? > > It should be possible to use the container_of macro to get the parent > dentry struct. Then, you can get the parent dentry d_parent and access > its inode. (Please correct me, if I'm wrong. I didn't test it). > Okay, I tried container_of, but it did not work. So I tried d_obtain_alias() which worked. But I am not sure if I have to make a call to dput() as well in order to free the dentry obtained. Anyone can confirm this? J > > > Philipp > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies(a)kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies -- J

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fork() and exec()
by Vijay Chauhan Feb. 8, 2012

Feb. 8, 2012

Hi List, I am learning Linux and trying to understand exec and fork function. execl says that it overlays the running address space. What does it mean? I created the following program and used top command with intentionally wrong arguments: #include<stdio.h> #include<unistd.h> #include<sys/types.h> #include<stdlib.h> int main(){ int a = -1; if(fork()==0){ printf("Inside child\n"); printf("child pid=%d, parentid=%d\n", getpid(), getppid()); execl("/usr/bin/top", "/usr/bin/top", ">/dev/null" ,(char*)0 ); scanf("inside child provide a %d", &a); printf("Inside child a=%d\n", a); exit(1); } else { printf("Inside parent, going to wait\n"); printf("my pid=%d, parentid=%d\n", getpid(), getppid()); scanf("input parent %d\n", &a); wait(NULL); printf("Wait over\n"); printf("Inside parent a=%d\n", a); } return 0; } When i run this program, it gives following output: [vijay@localhost]$ ./a.out Inside parent, going to wait Inside child child pid=2775, parentid=2774 my pid=2774, parentid=2681 top: unknown argument '>' usage: top -hv | -bcisSHM -d delay -n iterations [-u user | -U user] -p pid [,pid ...] 10 Wait over Inside parent a=-1 [vijay@localhost]$ Why the child scanf and printf not executed? In the parent program, i expected input parent should be printed. But it doesnt and just wait for some input. When i entered 10 it resumes but printing -1 as a value. Could anyone please help me to understand this behavior? or any good tutorial or book Thanks. Vijay

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Re: Kernelnewbies Digest, Vol 15, Issue 12
by Mayank Agarwal Feb. 8, 2012

Feb. 8, 2012

Hi all, I want to contribute to camera dri*vers in linux kernel*.Please guide me the procedure of doing that. Regards, Mayank On Tue, Feb 7, 2012 at 10:30 PM, <kernelnewbies-request(a)kernelnewbies.org>wrote: > Send Kernelnewbies mailing list submissions to > kernelnewbies(a)kernelnewbies.org > > To subscribe or unsubscribe via the World Wide Web, visit > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > or, via email, send a message with subject or body 'help' to > kernelnewbies-request(a)kernelnewbies.org > > You can reach the person managing the list at > kernelnewbies-owner(a)kernelnewbies.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Kernelnewbies digest..." > > > Today's Topics: > > 1. Re: "Trying to free already-free IRQ 9", but it wasn't freed > by me (mayur nande) > 2. Re: request_firmware question (Greg KH) > 3. Re: fork() and exec() (Bernd Petrovitsch) > 4. Re: make config errors while building kernel on Fedora 16 > (Kartik Singhal) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Tue, 7 Feb 2012 20:33:31 +0530 > From: mayur nande <mayur.nan(a)gmail.com> > Subject: Re: "Trying to free already-free IRQ 9", but it wasn't freed > by me > To: "nils.stec" <nils.stec(a)googlemail.com> > Cc: kernelnewbies <Kernelnewbies(a)kernelnewbies.org> > Message-ID: > <CA%2BfM3Xy2QALrjbTYJxW0yKn-Q-Y99Wi8xUyyWtKEzYDTByTkjQ(a)mail.gmail.com > > > Content-Type: text/plain; charset="iso-8859-1" > > Hi Nils, > > >>void cleanup_module(void) { > >> ... > >> free_irq(ADC_IRQ, NULL); /* remove interrupt handler */ > >> ... > >> return; > >>} > > You should not pass NULL here. It should be the unique cookie that you > passed in request_irq (adc_irq_handler in your case) since you have used > IRQF_SHARED which means you want to share your interrupt line. Also check > whether you really want to share your interrupt line and also if you want > to use "(void *)(adc_irq_handler)" as the unique identification. > > HTH! > > Regards > Mayur > > On Tue, Feb 7, 2012 at 7:45 PM, nils.stec <nils.stec(a)googlemail.com> > wrote: > > > Hi, > > > > atm I'm writing a kernel module for an embedded ARM device. > > This module uses IRQ9. > > > > If i remove the module, the kernel tells me that: > > > > ------------[ cut here ]------------ > > WARNING: at kernel/irq/manage.c:858 __free_irq+0x84/0x154() > > Trying to free already-free IRQ 9 > > Modules linked in: adc_demo_irq(P-) g_ether pegasus mii > > [<c0028794>] (unwind_backtrace+0x0/0xd0) from [<c003b504>] > > (warn_slowpath_common+0x48/0x60) > > [<c003b504>] (warn_slowpath_common+0x48/0x60) from [<c003b554>] > > (warn_slowpath_fmt+0x24/0x30) > > [<c003b554>] (warn_slowpath_fmt+0x24/0x30) from [<c005fa00>] > > (__free_irq+0x84/0x154) > > [<c005fa00>] (__free_irq+0x84/0x154) from [<c005fb0c>] > > (free_irq+0x3c/0x5c) > > [<c005fb0c>] (free_irq+0x3c/0x5c) from [<bf01e18c>] > > (cleanup_module+0x4c/0x60 [adc_demo_irq]) > > [<bf01e18c>] (cleanup_module+0x4c/0x60 [adc_demo_irq]) from [<c005b898>] > > (sys_delete_module+0x1c4/0x238) > > [<c005b898>] (sys_delete_module+0x1c4/0x238) from [<c0022dc0>] > > (ret_fast_syscall+0x0/0x28) > > ---[ end trace 60d7a16d878ac0b3 ]--- > > adc testing module removed > > ------------[ cut here ]------------ > > > > The message "adc testing module removed" comes from my module > **after**free_irq() via printk, so the module exit routine works till the > end. > > > > This is my code (only the IRQ related part): > > > > irqreturn_t adc_irq_handler(int irq, void *dev_id) { > > > > ... do someting ... > > > > return IRQ_HANDLED; > > } > > > > int init_module(void) { > > int32_t retval; > > ... > > retval = request_irq(ADC_IRQ, adc_irq_handler, IRQF_SHARED, "lpc313x > > adc irq", (void *)(adc_irq_handler)); > > ... > > return retval; > > } > > > > void cleanup_module(void) { > > ... > > free_irq(ADC_IRQ, NULL); /* remove interrupt handler */ > > ... > > return; > > } > > > > > > I hope anyone of you can help me with that problem. If you need more > > information, i'll send it > > > > Greetings, > > Nils > > > > _______________________________________________ > > Kernelnewbies mailing list > > Kernelnewbies(a)kernelnewbies.org > > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > > > >

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parent inode from the current struct inode
by Jack David Feb. 8, 2012

Feb. 8, 2012

Hi All, Is possible to get parent directory's inode structure from the current inode? If so, how can I do that? Also, is it possible to get the "struct file" if we have "struct inode" ?? Thanks, J

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/proc question
by Surenkumar Nihalani Feb. 8, 2012

Feb. 8, 2012

Hello All, I am writing a kernel module and I wanted to know which data structure backs up the /proc/self or how do I get the process id of my call and number of it's threads from within the kernel? Thanks, Suren.

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make config errors while building kernel on Fedora 16
by Kartik Singhal Feb. 7, 2012

Feb. 7, 2012

Hi I tried to build both linux mainline and linux-next on my Fedora 16 box. But in both cases I am running into errors in making the .config Here is a what is written (partial from top) to stdout: *** Default configuration is based on 'x86_64_defconfig' init/Kconfig:237:warning: multi-line strings not supported kernel/irq/Kconfig:75:warning: multi-line strings not supported init/Kconfig:667:warning: multi-line strings not supported init/Kconfig:1216:warning: multi-line strings not supported init/Kconfig:1307:warning: multi-line strings not supported init/Kconfig:1308:warning: multi-line strings not supported And the following (partial from bottom) to stderr: drivers/vhost/Kconfig:10: syntax error drivers/vhost/Kconfig:9: unknown option "To" drivers/vhost/Kconfig:10: unknown option "be" drivers/lguest/Kconfig:12: syntax error drivers/lguest/Kconfig:11: unknown option "Note" drivers/lguest/Kconfig:12: unknown option "not" drivers/lguest/Kconfig:15: syntax error drivers/lguest/Kconfig:14: unknown option "If" lib/xz/Kconfig:59: syntax error lib/xz/Kconfig:58: unknown option "Unless" lib/xz/Kconfig:59: unknown option "and" lib/Kconfig:281: syntax error lib/Kconfig:280: unknown option "If" make[1]: *** [defconfig] Error 1 make: *** [defconfig] Error 2 I have verified that I have buildtools, kernel-devel and header packages. And last month I had built the kernel (mainline) for first time on Linux Mint. But here, probably, I am missing something completely. Google search didn't help much either. -- Kartik http://k4rtik.wordpress.com/

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"Trying to free already-free IRQ 9", but it wasn't freed by me
by nils.stec Feb. 7, 2012

Feb. 7, 2012

Hi, atm I'm writing a kernel module for an embedded ARM device. This module uses IRQ9. If i remove the module, the kernel tells me that: ------------[ cut here ]------------ WARNING: at kernel/irq/manage.c:858 __free_irq+0x84/0x154() Trying to free already-free IRQ 9 Modules linked in: adc_demo_irq(P-) g_ether pegasus mii [<c0028794>] (unwind_backtrace+0x0/0xd0) from [<c003b504>] (warn_slowpath_common+0x48/0x60) [<c003b504>] (warn_slowpath_common+0x48/0x60) from [<c003b554>] (warn_slowpath_fmt+0x24/0x30) [<c003b554>] (warn_slowpath_fmt+0x24/0x30) from [<c005fa00>] (__free_irq+0x84/0x154) [<c005fa00>] (__free_irq+0x84/0x154) from [<c005fb0c>] (free_irq+0x3c/0x5c) [<c005fb0c>] (free_irq+0x3c/0x5c) from [<bf01e18c>] (cleanup_module+0x4c/0x60 [adc_demo_irq]) [<bf01e18c>] (cleanup_module+0x4c/0x60 [adc_demo_irq]) from [<c005b898>] (sys_delete_module+0x1c4/0x238) [<c005b898>] (sys_delete_module+0x1c4/0x238) from [<c0022dc0>] (ret_fast_syscall+0x0/0x28) ---[ end trace 60d7a16d878ac0b3 ]--- adc testing module removed ------------[ cut here ]------------ The message "adc testing module removed" comes from my module *after* free_irq() via printk, so the module exit routine works till the end. This is my code (only the IRQ related part): irqreturn_t adc_irq_handler(int irq, void *dev_id) { ... do someting ... return IRQ_HANDLED; } int init_module(void) { int32_t retval; ... retval = request_irq(ADC_IRQ, adc_irq_handler, IRQF_SHARED, "lpc313x adc irq", (void *)(adc_irq_handler)); ... return retval; } void cleanup_module(void) { ... free_irq(ADC_IRQ, NULL); /* remove interrupt handler */ ... return; } I hope anyone of you can help me with that problem. If you need more information, i'll send it Greetings, Nils

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Re: make config errors while building kernel on Fedora 16
by Mulyadi Santosa Feb. 7, 2012

Feb. 7, 2012

Hi :) Don't forget to cc: to kernelnewbies as well... On Mon, Feb 6, 2012 at 15:05, Kartik Singhal <kartiksinghal(a)gmail.com> wrote: > I cloned from repo url's given at kernel.org: > > nohup git clone -v > git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git &> > linux.log & > > and > > nohup git clone -v > git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git &> > linux-next.log & > > AFAIK checksum is not needed with a git clone. Looking at your make defconfig, I guess the source is somehow broken. But I can't tell exactly why. -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com

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[OOT]: crash / kdump query
by Adil Mujeeb Feb. 7, 2012

Feb. 7, 2012

Hi List, I am new to crash / kdump tool and failing some problem as mentioned below. I am referring the Linux Kernel Crash Book (http://www.dedoimedo.com/) and URL http://www.dedoimedo.com/computers/crash.html. I am building modified kernel source (2.6.32 based) and added my modules (for study purpose). Building, installing and booting kernel is successful. I have enabled the options for kdump as mentioned in the book: Enable Kexec system call: CONFIG_KEXEC=y Enable kernel crash dumps: CONFIG_CRASH_DUMP=y Optional: Disable Symmetric Multi-Processing (SMP) support CONFIG_SMP=y Enable sysfs file system support: CONFIG_SYSFS=y Enable /proc/vmcore support: CONFIG_PROC_VMCORE=y Configure the kernel with debug info: CONFIG_DEBUG_INFO=y Configure the start section for reserved RAM for the crash kernel: CONFIG_PHYSICAL_START=0x200000 (2MB) Configure kdump kernel so it can be identified: CONFIG_LOCALVERSION="-crash" Kdump configuration /etc/sysconfig/kdump: KDUMP_KERNELVER="" KDUMP_COMMANDLINE="" KDUMP_COMMANDLINE_APPEND="maxcpus=1 " KEXEC_OPTIONS="" KDUMP_IMMEDIATE_REBOOT="yes" KDUMP_TRANSFER="" KDUMP_SAVEDIR="file:///var/crash" KDUMP_KEEP_OLD_DUMPS="5" KDUMP_FREE_DISK_SIZE="64" KDUMP_VERBOSE="3" KDUMP_DUMPLEVEL="0" KDUMP_DUMPFORMAT="compressed" There is no option KDUMP_DUMPDEV option There is no option KDUMP_RUNLEVEL I booted successfully with this kernel and tried to crash it by module. After rebooting, I found that vmcore is generated under /var/crash/ But I am not able to analyze it with crash command. linux:/home/adil # cat /proc/cmdline root=/dev/disk/by-id/ata-WDC_WD800BD-22LRA1_WD-WMAM9ZS19445-part1 resume=/dev/disk/by-id/ata-WDC_WD800BD-22LRA1_WD-WMAM9ZS19445-part2 splash=silent crashkernel=256M-:128M vga=0x31a linux:/home/adil # linux:/home/adil # crash /boot/System.map-2.6.32.12-crash-crash /boot/vmlinuz-2.6.32.12-crash-crash crash 5.0.1 Copyright (C) 2002-2010 Red Hat, Inc. Copyright (C) 2004, 2005, 2006 IBM Corporation Copyright (C) 1999-2006 Hewlett-Packard Co Copyright (C) 2005, 2006 Fujitsu Limited Copyright (C) 2006, 2007 VA Linux Systems Japan K.K. Copyright (C) 2005 NEC Corporation Copyright (C) 1999, 2002, 2007 Silicon Graphics, Inc. Copyright (C) 1999, 2000, 2001, 2002 Mission Critical Linux, Inc. This program is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Enter "help copying" to see the conditions. This program has absolutely no warranty. Enter "help warranty" for details. crash: /boot/vmlinuz-2.6.32.12-crash-crash: not a supported file format Usage: crash [-h [opt]][-v][-s][-i file][-d num] [-S] [mapfile] [namelist] [dumpfile] Enter "crash -h" for details. linux:/home/adil # The URL http://www.dedoimedo.com/computers/crash.html mentioned that "The newer versions of Kdump can work with compressed kernel images. Furthermore, they copy the System map file and the kernel image into the crash directory, making the use of crash utility somewhat simpler." linux:/home/adil # ls -al /var/crash/2012-01-30-18\:08/ total 1335536 drwxr-xr-x 2 root root 4096 2012-01-30 18:13 . drwxr-xr-x 8 root root 4096 2012-01-31 12:17 .. -rw-r--r-- 1 root root 187 2012-01-30 18:13 README.txt -rw-r--r-- 1 root root 1716605 2012-01-30 18:13 System.map-2.6.32.12-0.7-default -rw------- 1 root root 1360732590 2012-01-30 18:13 vmcore -rw-r--r-- 1 root root 3774506 2012-01-30 18:13 vmlinux-2.6.32.12-0.7-default.gz linux:/home/adil # ls -al /var/crash/2012-01-31-12\:17/ total 1343860 drwxr-xr-x 2 root root 4096 2012-01-31 12:24 . drwxr-xr-x 8 root root 4096 2012-01-31 12:17 .. -rw-r--r-- 1 root root 187 2012-01-31 12:24 README.txt -rw------- 1 root root 1374748735 2012-01-31 12:24 vmcore linux:/home/adil # linux:/home/adil # ls /boot/ backup_mbr boot boot.readme config-2.6.32.12-0.7-default config-2.6.32.12-0.7-xen grub initrd initrd-2.6.32.12-0.7-default initrd-2.6.32.12-0.7-default-kdump initrd-2.6.32.12-0.7-xen initrd-2.6.32.12-crash-crash initrd-2.6.32.12-crash-crash-kdump initrd-xen message symsets-2.6.32.12-0.7-default.tar.gz symtypes-2.6.32.12-0.7-default.gz symvers-2.6.32.12-0.7-default.gz symvers-2.6.32.12-0.7-xen.gz System.map-2.6.32.12-0.7-default System.map-2.6.32.12-0.7-xen System.map-2.6.32.12-crash-crash vmlinux-2.6.32.12-0.7-xen.gz vmlinuz vmlinuz-2.6.32.12-0.7-default vmlinuz-2.6.32.12-0.7-xen vmlinuz-2.6.32.12-crash-crash vmlinuz-xen vmlinux-2.6.32.12-0.7-default.gz linux:/home/adil # Another observation is boot.kdump seems to on but manually start giving me error: linux:/home/adil # chkconfig boot.kdump boot.kdump on linux:/home/adil # linux:/home/adil # /etc/init.d/boot.kdump start Loading kdump Regenerating kdump initrd ... Can't find kernel text map area from kcore Cannot load /boot/vmlinuz-2.6.32.12-crash-crash failed linux:/home/adil # Other Query: Following is not clear mentioned in the book under "section 11.2 Crash (capture) kernel": -------------- This means that while your production kernels will most likely be named vmlinuz, the Kdump crash kernels need to be uncompressed, hence named vmlinux, or rather vmlinux-kdump. --------------- Please help how to correctly setup and use crash on my machine. Thank you, Adil

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Softlock OOPS dump
by devendra rawat Feb. 7, 2012

Feb. 7, 2012

Hi All, I am having a PPC system running Windriver linux. System is restarting because of watchdog. System was restated because no scheduling took place for 15.7 seconds. I want to figure out which function/ISR/routine was the kernel executing when this softlockup happened and at what place was the execution going. The NIP (next instruction pointer) reg. is not giving the symbol name as the "switch" module that created the problem was dynamically loaded. Can anybody help in figuring out the exact routine that may be behind the lockup. I am getting the following OOPS. cpu0: jiffies: 1903983223, hrtime: 16746998586843980, 15756 ms between scheduler_tick() calls 31/12/1969 EST 19:00:00, BUG: soft lockup detected on CPU#0! 31/12/1969 EST 19:00:00, NIP: C0041FAC LR: C0042320 SP: C71AFB10 REGS: c71afa60 TRAP: 0901 Tainted: P 31/12/1969 EST 19:00:00, MSR: 00009032 EE: 1 PR: 0 FP: 0 ME: 1 IR/DR: 11 31/12/1969 EST 19:00:00, TASK = cef2c880[1224] 'switch' THREAD: c71ae000 31/12/1969 EST 19:00:00, Last syscall: 54 31/12/1969 EST 19:00:00, 31/12/1969 EST 19:00:00, GPR00: 31/12/1969 EST 19:00:00, C017D5E4 31/12/1969 EST 19:00:00, C71AFB10 31/12/1969 EST 19:00:00, CEF2C880 31/12/1969 EST 19:00:00, 00000020 31/12/1969 EST 19:00:00, C71AFC20 31/12/1969 EST 19:00:00, D04C7F80 31/12/1969 EST 19:00:00, C036A774 31/12/1969 EST 19:00:00, 0000001C 31/12/1969 EST 19:00:00, 31/12/1969 EST 19:00:00, GPR08: 31/12/1969 EST 19:00:00, C036BF48 31/12/1969 EST 19:00:00, 00000000 31/12/1969 EST 19:00:00, 0000F10C 31/12/1969 EST 19:00:00, 00000000 31/12/1969 EST 19:00:00, 2410C042 31/12/1969 EST 19:00:00, 31/12/1969 EST 19:00:00, NIP [c0041fac] 31/12/1969 EST 19:00:00, handle_IRQ_event+0x254/0x4d4 31/12/1969 EST 19:00:00, LR [c0042320] 31/12/1969 EST 19:00:00, __do_IRQ+0xf4/0x164 31/12/1969 EST 19:00:00, Call trace 31/12/1969 EST 19:00:00, 31/12/1969 EST 19:00:00, [c0042320] 31/12/1969 EST 19:00:00, __do_IRQ+0xf4/0x16 31/12/1969 EST 19:00:00, 31/12/1969 EST 19:00:00, [c0006c64] 31/12/1969 EST 19:00:00, do_IRQ+0x54/0x10 31/12/1969 EST 19:00:00, 31/12/1969 EST 19:00:00, [c0005214] 31/12/1969 EST 19:00:00, ret_from_except+0x0/0x1 31/12/1969 EST 19:00:00, 31/12/1969 EST 19:00:00, [e10cbc7c] 31/12/1969 EST 19:00:00, bcm_bsa_request+0x189c/0x4140 [bcm5690 31/12/1969 EST 19:00:00, 31/12/1969 EST 19:00:00, [e10d09a8] 31/12/1969 EST 19:00:00, bcm_ioctl+0x144/0x480 [bcm5690 31/12/1969 EST 19:00:00, 31/12/1969 EST 19:00:00, [c0087764] 31/12/1969 EST 19:00:00, do_ioctl+0x68/0x9 31/12/1969 EST 19:00:00, 31/12/1969 EST 19:00:00, [c0087850] 31/12/1969 EST 19:00:00, vfs_ioctl+0xb8/0x40 31/12/1969 EST 19:00:00, 31/12/1969 EST 19:00:00, [c0087e00] 31/12/1969 EST 19:00:00, sys_ioctl+0x268/0x38 31/12/1969 EST 19:00:00, 31/12/1969 EST 19:00:00, [c0004a1c] 31/12/1969 EST 19:00:00, DoSyscall_no_dpa_entry+0x74/0x9 /*****************************/ Thanks in advance. Devendra.

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