Alan Cox | 1 May 01:30 2012
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Re: tty driver

On Mon, 30 Apr 2012 14:17:30 -0400
Sri Ram Vemulpali <sri.ram.gmu06 <at> gmail.com> wrote:

> Hello All,
> 
> I am working on paging feature on tty, pty outputting. Is there anyway
> I can do paging output at tty drivers by way of setting some options
> using ioctl or ....

Things like page dimensions and escape code management are userspace
handled in Linux. If you must fake it via a tty then I'd suggest you
write a pty/tty using app, if not then pipe it through more.

For the former case a simple expect script should do it.
Greg Ungerer | 1 May 08:55 2012

Re: [Q] TinyLinux project status (resend)

On 29/04/12 11:02, Rob Landley wrote:
> On 04/28/2012 08:09 AM, Greg Ungerer wrote:
>> On 04/28/2012 04:15 PM, Rob Landley wrote:
>>> On 04/27/2012 01:08 AM, Greg Ungerer wrote:
>>>> On 26/04/12 15:14, Rob Landley wrote:
>>>>>> I have also been able to boot an ARM noMMU kernel for the AT91x40 SoC
>>>>>> under SkyEye. This time, the userspace works fine. I haven't had the
>>>>>> time to clean up this, and it requires patches to both the kernel and
>>>>>> SkyEye to work properly. If you're interested, I'll give you these
>>>>>> patches and configs when I'm done with the cleanup.
>>>>>
>>>>> I'm unlikely to play with skyeye (tried it once, but it was years ago).
>>>>>
>>>>> Is there a strong reason nommu kernel's won't run on hardware or an
>>>>> emulator that _does_ implement an mmu? (Can't it just not use it?)
>>>>
>>>> No. It comes down to architectural support. There are a few that do
>>>> it. I have ColdFire hardware with MMU, it can be compiled and run
>>>> either with or without MMU enabled (by flicking the kernel's
>>>> CONFIG_MMU switch).
>>>
>>> Architectural support in the kernel, or in the emulator?
>>
>> In the kernel. For arches that don't currently do any non-mmu it is
>> usually the code in arch/foobar/mm and often some in arch/foobar/kernel
>> that has no concept of operating with the MMU turned off.
>
> Surely there's a way to genericize this.  Even on processors that don't
> _come_ without an mmu, in ultra-low-memory environments doing without
> page tables can still be a win sometimes...
(Continue reading)

Bill Traynor | 1 May 15:29 2012

immutable wiki?

I have an Editor account for the kernelnewbies.org wiki, but all pages
are currently immutable.  Was the wiki made read-only at some point?

Thanks
Bill
Anuz Pratap Singh Tomar | 1 May 15:45 2012
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Re: immutable wiki?



On Tue, May 1, 2012 at 2:29 PM, Bill Traynor <wmat <at> alphatroop.com> wrote:
I have an Editor account for the kernelnewbies.org wiki, but all pages
are currently immutable.  Was the wiki made read-only at some point?

I just modified my own article with minor changes to test. It seems to be working fine for me.

Regards
Anuz
Thanks
Bill

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Jim Cromie | 1 May 20:36 2012
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please report distros with CONFIG_DYNAMIC_DEBUG, using ddebug_query= boot param

hi all,

Ive been asked whether ddebug_query= boot param is used in any distros,
I think the question seeks to determine a good deprecation schedule for it
(its been obsoleted by dyndbg= in driver-core-next)

Would you all be so kind as to check your favorite distros, and report
the ones that
have one or both ?

Ubuntu 12.04 LTS lacks it:

jimc <at> chumly:~/projects/lx/linux-2.6$ grep DYNAMIC_DEBUG /boot/config*
/boot/config-3.0.0-17-generic:# CONFIG_DYNAMIC_DEBUG is not set
/boot/config-3.2.0-24-generic:# CONFIG_DYNAMIC_DEBUG is not set

Voyage linux also lacks it, (also debian based)

Fedora-16 has config option:

$ uname -a
Linux groucho.jimc.earth 3.3.2-6.fc16.x86_64 #1 SMP Sat Apr 21
12:43:20 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
$ grep DYNAMIC_DEBUG /boot/config-3.3.*
/boot/config-3.3.1-5.fc16.x86_64:CONFIG_DYNAMIC_DEBUG=y
/boot/config-3.3.2-1.fc16.x86_64:CONFIG_DYNAMIC_DEBUG=y
/boot/config-3.3.2-6.fc16.x86_64:CONFIG_DYNAMIC_DEBUG=y

but its not used by default. I have modified my grub defaults:

$ grep ddebug_query /etc/default/grub
GRUB_CMDLINE_LINUX='quiet rhgb loglevel=8 ddebug_query="module params
+p" dynamic_debug.verbose=1 nouveau.dyndbg nouveau.force_post=1
it87.dyndbg=+p nouveau.perflvl_wr=7777'

FYI, the above usage will eventually be unsupported,
it can be replaced in driver-core-next by either of:

  dyndbg="module params +p"
  params.dyndbg=+p
  params.dyndbg          # defaults to +p

the 2nd, 3rd forms also work for loadable modules (though params isnt
one of them)

thanks in advance
Jim
michi1 | 2 May 12:52 2012

Re: immutable wiki?

Hi!

On 09:29 Tue 01 May     , Bill Traynor wrote:
> I have an Editor account for the kernelnewbies.org wiki, but all pages
> are currently immutable.  Was the wiki made read-only at some point?

You must be on http://kernelnewbies.org/EditorsGroup to make changes. This
was made for spam procection. Everybody who is on the list can add you. What
is your username in the wiki?

	-Michi
--

-- 
programing a layer 3+4 network protocol for mesh networks
see http://michaelblizek.twilightparadox.com
Bill Traynor | 2 May 14:06 2012

Re: immutable wiki?

On Wed, May 2, 2012 at 6:52 AM,
<michi1 <at> michaelblizek.twilightparadox.com> wrote:
> Hi!
>
> On 09:29 Tue 01 May     , Bill Traynor wrote:
>> I have an Editor account for the kernelnewbies.org wiki, but all pages
>> are currently immutable.  Was the wiki made read-only at some point?
>
> You must be on http://kernelnewbies.org/EditorsGroup to make changes. This
> was made for spam procection. Everybody who is on the list can add you. What
> is your username in the wiki?

Thanks Michael, Rik already fixed it for me.

>
>        -Michi
> --
> programing a layer 3+4 network protocol for mesh networks
> see http://michaelblizek.twilightparadox.com
Panagiotis Sakkos | 2 May 15:43 2012
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Crash when sending a lot of messages through a unix socket

Hi,

I am trying to log information from within the kernel with the use of a unix socket (/dev/log).
My code is a kprobe handler, so while executing I am atomic and uninterrupted.
The crashes begin when I do stress tests against my module, so i.e. more than 50 logs per second.
The crash messages I get every time are different (from NULL reference, unable to handle page request etc), so I suppose that something is overwritten and this leads to the crash.
 
I don't want to post the code here because it ~100 LOC but these are my steps:

Initialization:
       call sock_create_kern, with PF_UNIX, SOCK_DGRAM, 0 and the address of my socket,
       then I memset to 0 my sockaddr_un variable and then I set its sun_family to PF_UNIX and copy the "/dev/log" string to sun_path

Logging:
    I have the message that I want to log in variable called buffer and its length in variable called message_length,
    I set the msg_name of the msghdr to the address of my sockaddr_un variable, than the msn_namelen to sizeof(sockadrr_un), the msg_iov to an iovec variable which contains the buffer and the message_length values, msg_iovlen to 1 and msg_control, msg_controllen to 0.
    Then I set the fs to KERNEL_DS, call sock_sendmsg with parameters my socket, the address of my msghdr and the message_length and then I restore the fs that there was before setting it to KERNEL_DS.

Please note that my socket, sockadd_un and my buffer are static variables. Also I always use the socket which is initialized once in the Initialization state (function).

Do you see any "bad practice" or something that could lead to crashes when stressing with a lot of messages the socket?

Thank you in advance!
Panos
--
http://www.cern.ch/psakkos
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Vimal | 2 May 18:17 2012
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Dropping one packet in a coalesced skb

Hi,

I have LSO enabled on my machine, and hence a single skb can
(possibly) be multiple packets on the wire.  I am writing a kernel
module that tries dropping packets.  Is there a way to drop just one
1500B sized TCP packet inside an skb that can be a 64KB TCP segment?
This segment has about 40 packets due to LSO, and I don't want to drop
all of them; just a few (2--3) packets.

Can the effect be achieved if I modify skb_shinfo(skb)->gso_segs, or nr_frags?

Thanks,
--

-- 
Vimal
Mulyadi Santosa | 2 May 19:55 2012
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Re: Crash when sending a lot of messages through a unix socket

Hi :)

On Wed, May 2, 2012 at 8:43 PM, Panagiotis Sakkos <panos.sakkos <at> cern.ch> wrote:
> Hi,
>
> I am trying to log information from within the kernel with the use of a unix
> socket (/dev/log).
> My code is a kprobe handler, so while executing I am atomic and
> uninterrupted.
> The crashes begin when I do stress tests against my module, so i.e. more
> than 50 logs per second.
>

Maybe that's the problem......under "rapid" call, kprobe handler must
allocate stack for unwinding the call more and more. Not to mention
that it began to push reentrancy problem to the surface.

Regarding reentrancy, IMO think like this...your handler called
once...ok fine, twice, perhaps still fine...but maybe more than 50 per
sec, not to mention the possibility that they are executed by more
than 1 core at once, perhaps that's the problem. race condition....

--

-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com

Gmane