[RFC] tcp: How does SACK or FACK determine the time to start fast retransmition?
HI all, When tcp uses reno as its congestion control algothim, it uses tp-sacked_out as dup-ack. When the third dup-ack(under default condition) comes, tcp will initiate its fast retransmition. But how about sack ? According to kernel source code comments, when sack or fack tcp option is enabled, there is no dup-ack counter. See comments for function tcp_dupack_heuristics(): http://lxr.linux.no/linux+v2.6.37/net/ipv4/tcp_input.c#L2300 So , how does tcp know the current dup-ack is the last one which triggers the fast retransmition? According to rfc3517 section 5: Upon the receipt of the first (DupThresh - 1) duplicate ACKs, the scoreboard is to be updated as normal. When a TCP sender receives the duplicate ACK corresponding to DupThresh ACKs, the scoreboard MUST be updated with the new SACK information (via Update ()). If no previous loss event has occurred on the connection or the cumulative acknowledgment point is beyond the last value of RecoveryPoint, a loss recovery phase SHOULD be initiated, per the fast retransmit algorithm outlined in [RFC2581]. But these sentences doesn't describe how tcp knows the current ack is the dup-threshold dup-ack. Accorrding to rfc3517 seciton 4 and isLost(Seqnum) function: The routine returns true when either DupThresh discontiguous SACKed sequences have arrived above ’SeqNum’ or (DupThresh * SMSS) bytes with sequence numbers greater than ’SeqNum’ have been SACKed. Otherwise, the routine returns false. I think this is just what I am searching for, but I still don't know which line of code in Linux tcp protocol does this check. Can any one help me ? thks in advance. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Sysfs class attribute problem
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Today's Topics:
1. RE: A confusion about invoking my syscall (Jeff Haran)
2. Re: Sysfs class attribute problem (Jeshwanth Kumar N K Jeshu)
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Message: 1
Date: Wed, 20 Jun 2012 16:58:30 +
From: Jeff Haran jha...@bytemobile.com
Subject: RE: A confusion about invoking my syscall
To: ?? wangzhe5...@gmail.com
Cc: kernelnewbies kernelnewbies@kernelnewbies.org
Message-ID:
4ab110e2fa959f41ac8480e84516371105b...@hq-ex01.bytemobile.com
Content-Type: text/plain; charset=iso-2022-jp
From: ?? [mailto:wangzhe5...@gmail.com]
Sent: Wednesday, June 20, 2012 1:16 AM
To: Jeff Haran
Cc: kernelnewbies
Subject: Re: A confusion about invoking my syscall
2012/6/20 Jeff Haran
jha...@bytemobile.commailto:jha...@bytemobile.com
From: ?? [mailto:wangzhe5...@gmail.commailto:wangzhe5...@gmail.com]
Sent: Monday, June 18, 2012 9:32 PM
To: Jeff Haran
Cc: kernelnewbies
Subject: Re: A confusion about invoking my syscall
2012/6/19 Jeff Haran
jha...@bytemobile.commailto:jha...@bytemobile.com
From: kernelnewbies-boun...@kernelnewbies.orgmailto:kernelnewbies-
boun...@kernelnewbies.org [mailto:kernelnewbies-
boun...@kernelnewbies.orgmailto:kernelnewbies-
boun...@kernelnewbies.org] On Behalf Of ??
Sent: Monday, June 18, 2012 6:40 PM
To: kernelnewbies
Subject: A confusion about invoking my syscall
Hello everyone:
I append a simple syscall in kernel. and the function is as
follows:
asmlinkage long sys_mysyscall(long data)
{
printk(This is my syscall!\n);
return data;
}
and i test it sucessfully in user space . and the test program:
#include linux/unistd.h
#include syscall.h
#include sys/types.h
#include stdio.h
int main(void)
{
long n = 0,m = 0,pid1,pid2;
n = syscall(345,190);// #define __NR_mysyscall 345
printf(n = %ld\n,n);
pid1 = syscall(SYS_getpid); //getpid
printf(pid = %ld\n,pid1);
pid2 = syscall(20); //getpid
printf(pid = %ld\n,pid2);
return 0;
}
and the result:
n = 190
pid = 4097
pid = 4097
but if the test program is:
#include linux/unistd.h
#include syscall.h
#include sys/types.h
#include stdio.h
int main(void)
{
long n = 0,m = 0,pid1,pid2;
n = syscall(345,190);// #define __NR_mysyscall 345
printf(n = %ld\n,n);
m = syscall(SYS_mysyscall,190);
printf(m = %ld\n,m);
pid1 = syscall(SYS_getpid); //getpid
printf(pid = %ld\n,pid1);
pid2 = syscall(20); //getpid
printf(pid = %ld\n,pid2);
return 0;
}
and the result:
wanny@wanny-C-Notebook-:~/syscall/src$ gcc test1.c
test1.c: In function ?main?:
test1.c:13:14: error: ?SYS_mysyscall? undeclared (first use in this
function)
test1.c:13:14: note: each undeclared identifier is reported only once
for each function it appears in
why i can't invoke my syscall with SYS_mysyscall?
Thanks in advance!
Because it appears you never defined the symbol SYS_mysyscall.
I think so,but where shoud i defne the symbol SYS_mysyscall ?
and where is the symbol SYS_getpid defined?
On my system /usr/include/bits/syscall.h, which is being included in
your program because it includes syscall.h.
83 #define SYS_getpid __NR_getpid ?so SYS_getpid is
replaced by __NR_getpid. and __NR_getpid was defined in the
kernel(arch/x86/include/asm/unistd_32.h). and my syscall was also
defined there.#define SYS_mysyscall __NR_mysyscall, i don't kown why it
doesn't works.
My sources contain no reference to SYS_mysyscall nor __NR_mysyscall, so
I assume you?ve added them to the Linux include files that you built
your module from.
User space programs like your main() program above generally aren?t
going to include Linux source tree include files. When you include
syscall.h from a user space program in a typical development
environment, the compiler is by default going to look for syscall.h in
/usr/include, not in the Linux source tree where presumably you?ve made
your modifications. Of course you can always tell the compiler to look
Re: [RFC] tcp: How does SACK or FACK determine the time to start fast retransmition?
On 20 June 2012 23:33, 李易 lovelyl...@gmail.com wrote: HI all, When tcp uses reno as its congestion control algothim, it uses tp-sacked_out as dup-ack. When the third dup-ack(under default condition) comes, tcp will initiate its fast retransmition. But how about sack ? According to kernel source code comments, when sack or fack tcp option is enabled, there is no dup-ack counter. See comments for function tcp_dupack_heuristics(): http://lxr.linux.no/linux+v2.6.37/net/ipv4/tcp_input.c#L2300 So , how does tcp know the current dup-ack is the last one which triggers the fast retransmition? With SACK, number of dupacks does not have much meaning. What matters is --how the SACK scoreboard looks like i.e. which packets are tagged Lost/Sacked/Retransmitted -- Whether FACK is in use (this assumes holes in between sacked packets are lost and have left the network and so we can send out more packets) So, stack does not count the number of dupacks that have come in. Only SACK blocks matter. You can try to track the following path: tcp_ack() deals with incoming acks and if it sees a dupack (does not matter what number), or incoming packet contains SACK it calls tcp_fastretrans_alert() which calls tcp_xmit_retransmit_queue(). tcp_xmit_retransmit_queue() decides which packets to retransmit. The first packet to start retransmitting from is tracked in tp-retransmit_skb_hint. Note that the dupThresh is actually tracked by tp-reordering which measures the reordering in the network and is not fixed at 3. So, if more than tp-reordering packets have been acked above a given packet, this packet is a candidate for retransmisson. See tcp_mark_head_lost() to see how the reordering metric is used to mark packets as lost. This corresponds to the check you mentioned in the RFC. So, window permitting, packets are sent as follows; (a)-- Packets marked lost as per description above (b)-- new packets (if any) (c)-- Holes between sacked packets which are not reliably lost. choice between (b) and (c) is made in tcp_can_forward_retransmit(). Hope this helps. Vijay ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: [RFC] tcp: How does SACK or FACK determine the time to start fast retransmition?
于 2012/6/21 16:42, Vijay Subramanian 写道: With SACK, number of dupacks does not have much meaning. What matters is --how the SACK scoreboard looks like i.e. which packets are tagged Lost/Sacked/Retransmitted -- Whether FACK is in use (this assumes holes in between sacked packets are lost and have left the network and so we can send out more packets) So, stack does not count the number of dupacks that have come in. Only SACK blocks matter. You can try to track the following path: tcp_ack() deals with incoming acks and if it sees a dupack (does not matter what number), or incoming packet contains SACK it calls tcp_fastretrans_alert() which calls tcp_xmit_retransmit_queue(). tcp_xmit_retransmit_queue() decides which packets to retransmit. The first packet to start retransmitting from is tracked in tp-retransmit_skb_hint. Note that the dupThresh is actually tracked by tp-reordering which measures the reordering in the network and is not fixed at 3. So, if more than tp-reordering packets have been acked above a given packet, this packet is a candidate for retransmisson. See tcp_mark_head_lost() to see how the reordering metric is used to mark packets as lost. This corresponds to the check you mentioned in the RFC. So, window permitting, packets are sent as follows; (a)-- Packets marked lost as per description above (b)-- new packets (if any) (c)-- Holes between sacked packets which are not reliably lost. choice between (b) and (c) is made in tcp_can_forward_retransmit(). Hope this helps. Vijay It is just I wanted! Thanks for your detailed explaination and kindness. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
download the source code of some commands
Hi all: I want to see some source code of some commands,for example,halt,reboot,uptime,and so on. but i don't kown where to download? can you give me some advice? Thanks in advance! ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: download the source code of some commands
How does it related to the kernel? On 6/21/12, 王哲 wangzhe5...@gmail.com wrote: Hi all: I want to see some source code of some commands,for example,halt,reboot,uptime,and so on. but i don't kown where to download? can you give me some advice? Thanks in advance! -- Regards, Denis ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Kernel Memory
Hi, I am a kernel newbie too, Kernel memory is not pagable, because kernel itself is responsible for paging. See this discussion, http://kerneltrap.org/node/6404 Paging happens for regular processes, i.e each process memory is divided into a page of certain size(4kb in Linux), so it can swap for another page that might be needed for that particular moment, it usually replaces an page that have not been used for long time(see LRU,internal fragmentation). Kernel is a process too, just like anyother process, but it differs from others because it directly talks to the hardware and also it is the one which takes care of paging and LRU algo's. So it does not make much sense, for a kernel memory to be pageable, because, if it removes the page that contains that has the paging algorithm, then there is no way to come back, you want to retrieve a page from disk_swap_area, but you cannot, because the page that contains code to retrieve the instructions are paged :)... This is not just for paging, since kernel controls everything, it is not advisable to put its own code in swap area(see, virtual memory, virtual memory = physical memory + swap space). BTW, i am a kernel newbie too, this is my basic understanding, please feel free to correct it, if I am wrong On Thu, Jun 21, 2012 at 8:27 AM, Vijay Chauhan kernel.vi...@gmail.comwrote: Hello, I am newbie. It has been said kernel memory is not pageable What does it mean? There is no concept of kernel virtual address? Any simple explanation will help me to udnerstand. Thanks, Vijay ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Kernel Memory
Hey Vijay I am a newbie too. Just sharing what I could go through. It is said that Kernel or atleast a part of kernel needs to be non paged for fast interrupt access etc as pinned memory Wiki says Pinned/Locked/Fixed pages Operating systems have memory areas that are pinned (never swapped to secondary storage). For example, interrupthttp://en.wikipedia.org/wiki/Interruptmechanisms rely on an array of pointers to their handlers, such as I/O http://en.wikipedia.org/wiki/I/O completion and page faulthttp://en.wikipedia.org/wiki/Page_fault. If the pages containing these pointers or the code that they invoke were pageable, interrupt-handling would become far more complex and time-consuming, particularly in the case of page fault interrupts. Hence, some part of the page table structures is not pageable. Some pages may be pinned for short periods of time, others may be pinned for long periods of time, and still others may need to be permanently pinned. For example: - The paging supervisor code and drivers for secondary storage devices on which pages reside must be permanently pinned, as otherwise paging wouldn't even work because the necessary code wouldn't be available. - Timing-dependent components may be pinned to avoid variable paging delays. - Data buffers http://en.wikipedia.org/wiki/Data_buffer that are accessed directly by peripheral devices that use direct memory accesshttp://en.wikipedia.org/wiki/Direct_memory_accessor I/O channels http://en.wikipedia.org/wiki/I/O_channel must reside in pinned pages while the I/O operation is in progress because such devices and the buses http://en.wikipedia.org/wiki/Bus_%28computing%29 to which they are attached expect to find data buffers located at physical memory addresses; regardless of whether the bus has a memory management unit for I/O http://en.wikipedia.org/wiki/IOMMU, transfers cannot be stopped if a page fault occurs and then restarted when the page fault has been processed. There are other two discussion thread which say kernel is non-pageable and now due to growing kernel Data structures it is allowed http://kerneltrap.org/node/6404 http://kerneltrap.org/node/8206 Regards Kishore On Thu, Jun 21, 2012 at 5:57 PM, Vijay Chauhan kernel.vi...@gmail.comwrote: Hello, I am newbie. It has been said kernel memory is not pageable What does it mean? There is no concept of kernel virtual address? Any simple explanation will help me to udnerstand. Thanks, Vijay ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: download the source code of some commands
王哲 wangzhe5...@gmail.com writes: Hi all: I want to see some source code of some commands,for example,halt,reboot,uptime,and so on. but i don't kown where to download? can you give me some advice? Thanks in advance! Hi, Although this does not relate to kernel, you can still view the codes of common linux/unix commands. ftp.gnu.org hosts most of commands in different packaging. Like coreutils, findutils, netutils etc. And standalone codes are there for grep, ed etc. You can also get a copy of freebsd dvd. Freebsd dvd's comes with full source code of the core system. cheers. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Kernel Memory
Hello Vijay, On Thu, Jun 21, 2012 at 5:57 PM, Vijay Chauhan kernel.vi...@gmail.com wrote: Hello, I am newbie. It has been said kernel memory is not pageable What does it mean? There is no concept of kernel virtual address? You might have heard about 3G/1G split. This 1GB is the virtual address of the kernel. And whenever kernel try to access any address in this range(for ARM architecture it is 0xC000 - 0x), there should not be any page fault. That means MMU should be able to convert your virtual address to physical. This 1GB contains your IO address, RAM address. Paging is a mechanism OS uses to pull the data(in pagesizes) to and fro between system RAM and secondary memory. Kernel memory is not pageable. This means memory allocated for the kernel will not be pagged out. If you try to access any memory in kernel with out creating page tables(this can be done by ioremap) you will end up in OOPS. The main reason of kernel not being swapable or pageable is as follows. Think this way. What will happen if we have paged out that portion of the logic which decides what to do when a page fault occurs? Who will take care of the page fault then? But if a user program hit a page fault(ie accessed address is not in main memory), kernel will load the page from secondary memory if it is a valid address. And if the address accesses is illegal, kernel kill the user application(Segmentation fault). Thanks, Arun Any simple explanation will help me to udnerstand. Thanks, Vijay ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Kernel Memory
Vijay Chauhan kernel.vi...@gmail.com writes: Hello, I am newbie. It has been said kernel memory is not pageable What does it mean? There is no concept of kernel virtual address? Yes. Kernel works on static adress space. Any simple explanation will help me to udnerstand. I'm not sure if you want to understand how kernel manages memory for its internal DS. If its the case you should read the following documents. 1) Read the chapter 8 of Linux Device driver 3rd edition. http://lwn.net/Kernel/LDD3/ 2) To understand slab allocator read the following papers by bonwick a) 94 paper describing slab allocator: http://static.usenix.org/publications/library/proceedings/bos94/full_papers/bonwick.a b) Its followup in 2001 http://static.usenix.org/event/usenix01/full_papers/bonwick/bonwick_html/index.html 3) These should be enough. But if you want to know detailed architecture of how virtual memory manager work you should read Gorman's book on Linux virtual memory manager. Its a free pdf. can be found here: http://ptgmedia.pearsoncmg.com/images/0131453483/downloads/gorman_book.pdf Happy hacking. Cheers aft Thanks, Vijay ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
RE: download the source code of some commands
Hello U can download coreutils from gnu.org. Sent from my HTC -- Send Kernelnewbies mailing list submissions to kernelnewbies@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-requ...@kernelnewbies.org You can reach the person managing the list at kernelnewbies-ow...@kernelnewbies.org When replying, please edit your Subject line so it is more specific than Re: Contents of Kernelnewbies digest... Message: 1 Date: Thu, 21 Jun 2012 18:17:36 +0800 From: ?? lovelyl...@gmail.com Subject: Re: [RFC] tcp: How does SACK or FACK determine the time to start fast retransmition? To: Vijay Subramanian subramanian.vi...@gmail.com Cc: netdev net...@vger.kernel.org, kernelnewbies@kernelnewbies.org Message-ID: 4fe2f4c0.4020...@gmail.com Content-Type: text/plain; charset=UTF-8; format=flowed ? 2012/6/21 16:42, Vijay Subramanian ??: With SACK, number of dupacks does not have much meaning. What matters is --how the SACK scoreboard looks like i.e. which packets are tagged Lost/Sacked/Retransmitted -- Whether FACK is in use (this assumes holes in between sacked packets are lost and have left the network and so we can send out more packets) So, stack does not count the number of dupacks that have come in. Only SACK blocks matter. You can try to track the following path: tcp_ack() deals with incoming acks and if it sees a dupack (does not matter what number), or incoming packet contains SACK it calls tcp_fastretrans_alert() which calls tcp_xmit_retransmit_queue(). tcp_xmit_retransmit_queue() decides which packets to retransmit. The first packet to start retransmitting from is tracked in tp-retransmit_skb_hint. Note that the dupThresh is actually tracked by tp-reordering which measures the reordering in the network and is not fixed at 3. So, if more than tp-reordering packets have been acked above a given packet, this packet is a candidate for retransmisson. See tcp_mark_head_lost() to see how the reordering metric is used to mark packets as lost. This corresponds to the check you mentioned in the RFC. So, window permitting, packets are sent as follows; (a)-- Packets marked lost as per description above (b)-- new packets (if any) (c)-- Holes between sacked packets which are not reliably lost. choice between (b) and (c) is made in tcp_can_forward_retransmit(). Hope this helps. Vijay It is just I wanted! Thanks for your detailed explaination and kindness. -- Message: 2 Date: Thu, 21 Jun 2012 17:57:22 +0530 From: Vijay Chauhan kernel.vi...@gmail.com Subject: Kernel Memory To: kernelnewbies@kernelnewbies.org Message-ID: CAJ61zBA++CFmTHSb2cRr=ckjdtkvyssvs3_igesbbf21gwa...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Hello, I am newbie. It has been said kernel memory is not pageable What does it mean? There is no concept of kernel virtual address? Any simple explanation will help me to udnerstand. Thanks, Vijay -- Message: 3 Date: Thu, 21 Jun 2012 20:48:48 +0800 From: ?? wangzhe5...@gmail.com Subject: download the source code of some commands To: kernelnewbies kernelnewbies@kernelnewbies.org Message-ID: cajrru3vhh719vzgccj3r8k842yemeo9d5_0swgqsgdnxe0v...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 Hi all: I want to see some source code of some commands,for example,halt,reboot,uptime,and so on. but i don't kown where to download? can you give me some advice? Thanks in advance! -- next part -- An HTML attachment was scrubbed... URL: http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20120621/3a198ac7/attachment-0001.html -- Message: 4 Date: Thu, 21 Jun 2012 05:53:00 -0700 From: ashish_bun...@dell.com Subject: RE: download the source code of some commands To: wangzhe5...@gmail.com, kernelnewbies@kernelnewbies.org Message-ID: a1a98fd909dc5248811a65c5d18e9c7635de8be...@blrx7mcdc202.amer.dell.com Content-Type: text/plain; charset=iso-2022-jp All commands are bin files. You should find the scripts for them in /usr/bin only. Ashish Bunkar Linux Engineering Dell | BDC office +91-80-28078131, mobile +91-7259183696 ashish_bun...@dell.commailto:narayana...@dell.com From: kernelnewbies-boun...@kernelnewbies.org [mailto:kernelnewbies-boun...@kernelnewbies.org] On Behalf Of ?? Sent: Thursday, June 21, 2012 6:19 PM To: kernelnewbies Subject: download the source code of some commands Hi all: I want to see some source code of some commands,for example,halt,reboot,uptime,and so on. but i don't kown where to download? can you give me some advice? Thanks in advance! -- next part -- An HTML attachment was scrubbed... URL: http
could some current.h files be simplified?
it *seems* as if a number of current.h files from various
architectures could be simplified. here's asm-generic/current.h,
which gives any architecture a generic starting point in defining both
get_current() and current:
#ifndef __ASM_GENERIC_CURRENT_H
#define __ASM_GENERIC_CURRENT_H
#include linux/thread_info.h
#define get_current() (current_thread_info()-task)
#define current get_current()
#endif /* __ASM_GENERIC_CURRENT_H */
and if that's acceptable, any architecture is welcome to simply
include it as, for instance, mips does in asm/current.h:
#include asm-generic/current.h
but here's the current.h file for parisc:
#ifndef _PARISC_CURRENT_H
#define _PARISC_CURRENT_H
#include linux/thread_info.h
struct task_struct;
static inline struct task_struct * get_current(void)
{
return current_thread_info()-task;
}
#define current get_current()
#endif /* !(_PARISC_CURRENT_H) */
i'm not sure i see why the generic version wasn't adequate for
parisc (apart from the explicit pointer casting). same thing with the
cris architecture and, i'm sure, others.
is there any reason why some of those current.h files can't just
include the generic one?
rday
--
Robert P. J. Day Ottawa, Ontario, CANADA
http://crashcourse.ca
Twitter: http://twitter.com/rpjday
LinkedIn: http://ca.linkedin.com/in/rpjday
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Re: download the source code of some commands
If you use Debian or other distribution with apt package system. You can use whereis to locate this command. [~]$ whereis halt halt: /sbin/halt /usr/share/man/man5/halt.5.gz /usr/share/man/man8/halt.8.gz Then, use dpkg -S to show which package it's included. This one is: sysvinit. [~]$ dpkg -S /sbin/halt sysvinit: /sbin/halt Now, you can download the source from Debian source, use: [~]$ apt-get source sysvinit Or if you want the original source, use aptitude (or apt-cache) find it's homepage. [~]$ aptitude show sysvinit Package: sysvinit .. Homepage: http://savannah.nongnu.org/projects/sysvinit At last, get it from there. As for other package systems, I think there should be a way too. Or you can google. On 2012-06-21 20:48:48 +0800, 王哲 wrote: Hi all: I want to see some source code of some commands,for example,halt,reboot,uptime,and so on. but i don't kown where to download? can you give me some advice? Thanks in advance! ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies -- Regards, Lei ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: download the source code of some commands
2012/6/21 Wang Lei f3d...@gmail.com If you use Debian or other distribution with apt package system. You can use whereis to locate this command. [~]$ whereis halt halt: /sbin/halt /usr/share/man/man5/halt.5.gz /usr/share/man/man8/halt.8.gz Then, use dpkg -S to show which package it's included. This one is: sysvinit. [~]$ dpkg -S /sbin/halt sysvinit: /sbin/halt Now, you can download the source from Debian source, use: [~]$ apt-get source sysvinit Or if you want the original source, use aptitude (or apt-cache) find it's homepage. [~]$ aptitude show sysvinit Package: sysvinit .. Homepage: http://savannah.nongnu.org/projects/sysvinit At last, get it from there. As for other package systems, I think there should be a way too. Or you can google. Thank you very much ! i follow your steps, and download the source code successfully. On 2012-06-21 20:48:48 +0800, 王哲 wrote: Hi all: I want to see some source code of some commands,for example,halt,reboot,uptime,and so on. but i don't kown where to download? can you give me some advice? Thanks in advance! ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies -- Regards, Lei ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Sysfs class attribute problem
Hello Anish
Thank you for the changes. Ya now I understoor dealing with store function.
:)
And I did small change in ur code.
I have declared the show and store function as I declared before.
static ssize_t attr1_store(struct class *cls, struct class_attribute *attr,
const char *buf, size_t count);
static ssize_t attr1_show(struct class *cls, struct class_attribute *attr,
char *buf);
instead.
static ssize_t attr1_store(struct class *cls, const char *buf, size_t
count);
static ssize_t attr1_show(struct class *cls, char *buf);
After this its working fine.
On Thu, Jun 21, 2012 at 9:04 AM, anish singh anish198519851...@gmail.comwrote:
On Wed, Jun 20, 2012 at 11:32 PM, Jeshwanth Kumar N K Jeshu
jeshkumar...@gmail.com wrote:
Hello
Thank you anish for the reply, the code is I pasted below.
[code-starts]
#include linux/init.h
#include linux/module.h
#include linux/kernel.h
#include linux/fs.h
#include linux/device.h
#include linux/sysdev.h
#include linux/major.h
#include asm/uaccess.h
#include linux/slab.h
#include linux/cdev.h
#include linux/kdev_t.h
static char *gvar = BeHonest;
// Store and Show functions..
static ssize_t attr1_store(struct class *cls, struct class_attribute
*attr,
const char *buf, size_t count);
static ssize_t attr1_show(struct class *cls, struct class_attribute
*attr,
char *buf);
static struct class_attribute pwm_class_attrs[] = {
__ATTR(attr1, S_IRUGO | S_IWUSR , attr1_show, attr1_store),
__ATTR_NULL
};
static struct class pwm_class =
{
.name = dev_jes,
.owner = THIS_MODULE,
.class_attrs = pwm_class_attrs
};
static int hello_init(void)
{
class_register(pwm_class);
printk(In hello_init function \n);
return 0;
}
static ssize_t attr1_show(struct class *cls, struct class_attribute
*attr,
char *buf)
{
printk(In attr1_show function\n);
return sprintf(buf, %s\n, gvar);
}
static ssize_t attr1_store(struct class *cls, struct class_attribute
*attr,
const char *buf, size_t count)
{
printk(the string is : %s\n,buf);
printk(In attr1_store function\n);
return 1;
//return sprintf(gvar, %s\n, buf); --- If I put this line
I
am getting ERROR :(
}
static void hello_exit(void)
{
class_unregister(pwm_class);
printk(In hello_exit function \n);
}
module_init(hello_init);
module_exit(hello_exit);
MODULE_LICENSE(GPL);
MODULE_AUTHOR(Jeshwanth);
MODULE_DESCRIPTION(Learning sysfs);
[code-ends]
echo jeshu /sys/class/dev_jes/attr1
And If I pass the command to atttribute I got result below in dmesg.
[ 3435.613057] the string is : jeshu
[ 3435.613061]
[ 3435.613066] In attr1_store function
[ 3435.613072] the string is : eshu
[ 3435.613074]
[ 3435.613078] In attr1_store function
[ 3435.613083] the string is : shu
[ 3435.613085]
[ 3435.613088] In attr1_store function
[ 3435.613093] the string is : hu
[ 3435.613095]
[ 3435.613098] In attr1_store function
[ 3435.613103] the string is : u
[ 3435.613105]
[ 3435.613108] In attr1_store function
[ 3435.613113] the string is :
[ 3435.613115]
[ 3435.613118] In attr1_store function
So please help me how to read the attribute in store function.. Thanks :)
#include linux/init.h
#include linux/module.h
#include linux/kernel.h
#include linux/fs.h
#include linux/device.h
#include linux/sysdev.h
#include linux/major.h
#include asm/uaccess.h
#include linux/slab.h
#include linux/cdev.h
#include linux/kdev_t.h
static char *gvar = NULL;
static ssize_t attr1_store(struct class *cls, const char *buf, size_t
count);
static ssize_t attr1_show(struct class *cls, char *buf);
static struct class_attribute pwm_class_attrs[] = {
__ATTR(attr1, 0666, attr1_show, attr1_store), //use macro for
permission
__ATTR_NULL
};
static struct class pwm_class =
{
.name = dev_jes,
.owner = THIS_MODULE,
.class_attrs = pwm_class_attrs
};
static int hello_init(void)
{
char string[] = nothing;
gvar = kmalloc(sizeof(char)*strlen(string), GFP_KERNEL);
class_register(pwm_class);
snprintf(gvar, sizeof(char)*strlen(string)+1, %s, string);
printk(anish In hello_init function \n);
return 0;
}
static ssize_t attr1_show(struct class *cls, char *buf)
{
printk(In attr1_show function\n);
printk(%s\n, gvar);
printk(In attr1_show function\n);
return sprintf(buf, %s, gvar);
}
static ssize_t attr1_store(struct class *cls, const char *buf, size_t
count)
{
printk(the string is : %s count %d\n, buf, count);
return snprintf(gvar, count, %s\n, buf);
}
static void hello_exit(void)
{
class_unregister(pwm_class);
printk(In hello_exit function \n);
}
module_init(hello_init);
module_exit(hello_exit);
Re: Kernelnewbies Digest, Vol 19, Issue 43
Debian source, use: [~]$ apt-get source sysvinit Or if you want the original source, use aptitude (or apt-cache) find it's homepage. [~]$ aptitude show sysvinit Package: sysvinit .. Homepage: http://savannah.nongnu.org/projects/sysvinit At last, get it from there. As for other package systems, I think there should be a way too. Or you can google. On 2012-06-21 20:48:48 +0800, ?? wrote: Hi all: I want to see some source code of some commands,for example,halt,reboot,uptime,and so on. but i don't kown where to download? can you give me some advice? Thanks in advance! ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies -- Regards, Lei -- Message: 4 Date: Thu, 21 Jun 2012 23:46:21 +0800 From: ?? wangzhe5...@gmail.com Subject: Re: download the source code of some commands To: Wang Lei f3d...@gmail.com Cc: kernelnewbies kernelnewbies@kernelnewbies.org Message-ID: cajrru3xdps620joe+q8w+siugvr3czzjohzg3e+pwssu5t0...@mail.gmail.com Content-Type: text/plain; charset=gb2312 2012/6/21 Wang Lei f3d...@gmail.com If you use Debian or other distribution with apt package system. You can use whereis to locate this command. [~]$ whereis halt halt: /sbin/halt /usr/share/man/man5/halt.5.gz /usr/share/man/man8/halt.8.gz Then, use dpkg -S to show which package it's included. This one is: sysvinit. [~]$ dpkg -S /sbin/halt sysvinit: /sbin/halt Now, you can download the source from Debian source, use: [~]$ apt-get source sysvinit Or if you want the original source, use aptitude (or apt-cache) find it's homepage. [~]$ aptitude show sysvinit Package: sysvinit .. Homepage: http://savannah.nongnu.org/projects/sysvinit At last, get it from there. As for other package systems, I think there should be a way too. Or you can google. Thank you very much ! i follow your steps, and download the source code successfully. On 2012-06-21 20:48:48 +0800, ?? wrote: Hi all: I want to see some source code of some commands,for example,halt,reboot,uptime,and so on. but i don't kown where to download? can you give me some advice? Thanks in advance! ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies -- Regards, Lei -- next part -- An HTML attachment was scrubbed... URL: http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20120621/6e586022/attachment-0001.html -- Message: 5 Date: Thu, 21 Jun 2012 17:48:25 +0200 From: mic...@michaelblizek.twilightparadox.com Subject: Re: Kernel Memory To: Vijay Chauhan kernel.vi...@gmail.com Cc: kernelnewbies@kernelnewbies.org Message-ID: 20120621154824.GA2280@grml Content-Type: text/plain; charset=us-ascii Hi! On 17:57 Thu 21 Jun , Vijay Chauhan wrote: Hello, I am newbie. It has been said kernel memory is not pageable What does it mean? There is no concept of kernel virtual address? Any simple explanation will help me to udnerstand. The right term is actually kernel memory is not swappable. Swapping means writing inactive memory to disk and then using it for something else. Kernel memory not being swappable is a design decicion made in the early linux days. Operating systems which swap kernel memory need to isolate everything which should not be swappd out (e.g. things needed for swap-in, realtime stuff, security sensitive data, ...). This is quite a bit of work. I also guess it is pretty pointless nowadays. Installed memory and is getting so huge that virtual memory developers have a hard time trying to keep cpu-usage overhead for swapping user space memory low. There is no concept of kernel virtual address? Kernel memory uses virtual addresses as well. However, these the entire system memory is continuously mapped somewhere in the virtual address space. The drawback is that fragmentation turns allocation of large continuous memory regions into a game of luck. There is also an virtual address area (vmalloc) which is used to dynamically map multiple scattered pages to a continuous region. But this is rather slow and rarely used. You might want to take a look at: http://lwn.net/Kernel/LDD3/ -Michi -- programing a layer 3+4 network protocol for mesh networks see http://michaelblizek.twilightparadox.com -- ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies End of Kernelnewbies Digest, Vol 19, Issue 43
