March 2011 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Questions about this patch: [PATCH] ARM: Use generic BUG() handler
by anish kumar March 17, 2011

March 17, 2011

https://lkml.org/lkml/2011/2/28/565 I have tested this patch on my system(linux 2.6.35-android) and it is working perfectly fine so wanted to understand this patch.Will this patch be included in mainline? I have few question from this thread.As my understanding of assembly is bit limited I would appreciate if someone can just say yes/no and probably add bit of words. > This implementation uses an undefined instruction to implement BUG, and > sets up > a bug table containing the relevant information. Many version of gcc do > not > support %c properly for ARM (inserting a # when they shouldn't) so we work > around this using distasteful macro magic. This undefined instruction should cause data abort ? > +#define BUG() _BUG(__FILE__, __LINE__, BUG_INSTR_VALUE) > +#define _BUG(file, line, value) __BUG(file, line, value) > +#define __BUG(__file, __line, __value) \ > +do { \ > + BUILD_BUG_ON(sizeof(struct bug_entry) != 12); \ > + asm volatile("1:\t" BUG_INSTR_TYPE #__value "\n" \ > + ".pushsection .rodata.str, \"aMS\", 1\n" \ > + "2:\t.asciz " #__file "\n" \ > + ".popsection\n" \ > + ".pushsection __bug_table,\"a\"\n" \ > + "3:\t.word 1b, 2b\n" \ > + "\t.hword " #__line ", 0\n" \ > + ".popsection"); \ > + unreachable(); \ > +} while (0) Above piece of code i couldn't understand.As i understand this should do same as original BUG() definition plus it should print the function where BUG() had originally happened instead of "PC at _bug".I think in this code some data(guess:function name ,line no) is pushed on the stack and then popped but how this data is printed on console? So kindly enlighten me on this piece of code or some pointers.Is there any thread which explains about kernel fault process?

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Linux hibernation
by Jacky Lam March 17, 2011

March 17, 2011

Hi all, I am looking at the source code 2.6.29 and find that Linux will make a copy of used memory pages when doing hibernation. I am curious, in this case, what Linux do if I have used over 50% of memory? Will hibernation just fail? I think it is not possible, but I can't understand from the code. Could any explain a little bit for me? Thanks. Jacky

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Cache disable verification
by Prabhu nath March 17, 2011

March 17, 2011

Dear All, Can you please let me know the way to find out whether the cache has been disabled or not on my embedded board. Regards, Prabhu

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fanotify enlightenment
by Belisko Marek March 17, 2011

March 17, 2011

Is there possibility to get some actual Documentation about fanotify interface (most of google results point to obsolete socket interface). I'm trying to use this (http://git.infradead.org/users/eparis/fanotify-example.git) example. Use 2.6.37 kernel with fanotify enabled trying to track file changes in my directory but no results when create new file of modify existing. Works only if point to existing file. Try sudo ./fanotify -o modify,open,close,access /home/* (end with Invalid argument) also without * at the end doesn't help. Any ideas why? Thanks in advance, Marek Belisko -- as simple and primitive as possible ------------------------------------------------- Marek Belisko - OPEN-NANDRA Freelance Developer Ruska Nova Ves 219 | Presov, 08005 Slovak Republic Tel: +421 915 052 184 skype: marekwhite icq: 290551086 web: http://open-nandra.com

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is git.kernel.org the best place for stable releases ?
by Jim Cromie March 16, 2011

March 16, 2011

OpenWrt is apparently using a stable release that isnt on kernel.org Bartman007 wrote: 23 November 2010 The OpenWrt Release Team would like to announce a fourth release candidate (RC4) for Backfire Interim Release 1 (10.03.1). Testing of this release candidate will allow further refinement of 10.03.1 * 2.6.32 targets updated from 2.6.32.16 to 2.6.32.25 OpenWrt 10.03 is running 2.6.32.10, which is still ahead of kernel.org http://git.kernel.org/?p=linux/kernel/git/smb/smb-2.6.32.y.git;a=commit;h=7… 2010-02-23 Greg Kroah... Linux 2.6.32.9 master origin/HEAD origin/master v2.6.32.9 stefan.bader(a)canonical.com is the branch/tree owner, ccd, FYI to kernelnewbies.

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RE:Limiting the Input Ethernet Throughput
by Praveen kumar March 16, 2011

March 16, 2011

Hi All, I want to limit my system input Ethernet through put to < 10MBps ,i e if i get the through put > 10mbps my system should not process it.I there any way to do it in the user space . I hope that we can achieve this by dig in in to driver .Is there any simpler way to do it?? Thanks and Regards, Praveen

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On sg_miter_next sg_miter_stop
by va stg2010 March 16, 2011

March 16, 2011

Hi Can someone explain to me reason for the comment at line 332-333 of this code http://lxr.linux.no/#linux+v2.6.27.7/lib/scatterlist.c#L332 comment is: " IRQ must stay disabled till @miter@ is stopped." Thankyou vks

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Re: FW: smart card driver (ricoh) with ubuntu
by Alexander Beregalov March 16, 2011

March 16, 2011

On 16 March 2011 17:22, Garcia, Alfredo (Sales) <alfredo.garcia-sanchez(a)hp.com> wrote: > Hi to all! > > I'm Alfredo Garcia, Bussines Developer in HP Spain. > > I,m searching a linux expert. > > I have a problem in ubuntu linux because I don't have the driver smartcard (ricoh) Ricoh Co Ltd RL5c476 II (don't exist the driver). We changes the smart card device in all new laptops and ricoh don't have the linux driver for the smart card. The smart card in integrated in the mother board. > > Is difficult develop a driver?? Could you make it? > Can you help me? RL5c476 II is flash card reader chip, not smart card. It seems modern linux should support it.

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Difference between qdisc and qdisc_sleeping, netdev_queue
by Henrique Rodrigues March 16, 2011

March 16, 2011

What is the difference between qdisc and qdisc_sleeping? (in struct netdev_queue, file include/linux/netdevice.h) I've been trying to find the answer to this question for a while, but I didn't succeed. Does anyone knows why we need both pointers in netdev_queue? In addition, there are 2 different locks related to these 2 ptrs in include/net/sch_generic.h: qdisc_root_lock() and qdisc_root_sleeping_lock(). Why we need both? Thanks, -- Henrique Rodrigues

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getconf CLK_TCK and CONFIG_HZ
by Jim Cromie March 16, 2011

March 16, 2011

Im trying to do a little benchmarking of perl, and have patched its distro files to run perl's times() function on each of the ~1900 test files. perl's times() uses man 2 times internally, which I presume reduces to a system-call The standard distro can be run as: HARNESS_TIMER=1 make test but this counts only wall-clock time, and is thus sensitive to system load. times does better, Anyway, the 1st thing I noticed on the times numbers was that they all have 10ms granularity. This agrees with sysconf granularity : $ getconf CLK_TCK 100 but not with linux kernel HZ: $ grep _HZ /boot/config-`uname -r` CONFIG_RCU_FAST_NO_HZ=y CONFIG_NO_HZ=y # CONFIG_HZ_100 is not set # CONFIG_HZ_250 is not set # CONFIG_HZ_300 is not set CONFIG_HZ_1000=y CONFIG_HZ=1000 Confusingly, man 2 times says : NOTES The number of clock ticks per second can be obtained using: sysconf(_SC_CLK_TCK); In POSIX.1-1996 the symbol CLK_TCK (defined in <time.h>) is mentioned as obsolescent. It is obsolete now. but linux (fedora 13) seems to disagree : $ getconf _SC_CLK_TCK getconf: Unrecognized variable `_SC_CLK_TCK' So, the Questions: Why arent they the same ? or what am I missing wrt the relationship between sysconf(CLK_TCK) and kernel HZ ? Is it possible to coax the kernel into counting times in 1ms via some cmd-line option ? I searched Documentation/kernel-parameters.txt, found nothing. is it possible to compile kernel with different HZ options to get the 1ms resolution ? Why doesnt times() also count IO-wait states for a process (and children) ? I note that top reports it (as a system-wide measure) and System Monitor 2.30.0 displays it (same system-wide measure) hypothetically, if IO-wait numbers were collected by times (API/ABI change, so never gonna happen) would it be able to reveal anything ? Id expect it to show measure disk activity due to the process, and arguably be sensitive to system load, unlike user, sys, child-user, child-sys numbers but it still sounds useful. Could process specific IO-wait numbers reveal anything about cache performance ? Do cache misses contribute to IO-wait, or do they get counted in other ways ?

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