Re: Merge Window closed, submitting patches?

[Justin Skists]

> On 26 August 2018 at 15:36 John Whitmore  wrote:
> 
> 
> My question is about what to do during the closed window? I don't think I
> should submit patches as I assume I'll create a backlog for the maintainer
> who'll possibly be flooded when the window re-opens. Similarly I could create
> patches but not send them until the window re-opens, but again I'll just be
> creating a backlog.

Just keep going. The maintainers will keep a queue of patches and then try to 
apply them in order when the merge window -rc1 is released for the next one.

Worse cases would be that the patches will no longer apply (in which case, a V2 
will be needed) or, if you haven't heard anything for a while after the -rc1, 
then a patch RESEND should do the trick.

Hope that helps,
Justin.

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Re: what is the purpose of "console_silent" in printk.h?

[Justin Skists]

> On 21 August 2018 at 13:41 rpj...@crashcourse.ca wrote:
> 
> 
> 
>i note in include/linux/printk.h:
> 
>static inline void console_silent(void)
>{
>   console_loglevel = CONSOLE_LOGLEVEL_SILENT;
>}
> 
> except i see no reference to "console_silent" anywhere else in the
> entire kernel code base. any idea what its purpose is?

It was used in an older version of the kernel. The architecture that used that 
function doesn't look like it is supported any more.

https://elixir.bootlin.com/linux/v4.16.18/source/arch/mn10300/kernel/mn10300-watchdog.c#L184


Justin.

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Re: Question about watchdog

[Justin Skists]

> On 02 July 2018 at 09:29 Greg KH  wrote:
> 
> 
> On Mon, Jul 02, 2018 at 08:58:16AM +0100, Justin Skists wrote:
> > 
> > > On 01 July 2018 at 13:44 bing zhu  wrote:
> > > 
> > > 
> > > Dear Sir/Ma'am
> > > Thank you for your time ,i'm a student new to linux kernel.at present ,i'd
> > > like to create a kernel thread
> > > say use kthread_create func ,my question is :how can i make this thread to
> > > run on a cpu and never get switched or scheduled , there is a
> > > while(1).structure in that thread i need it to do work . at present i
> > > comes with errors like "NMI watchdog: BUG: soft lockup - CPU#0 stuck for
> > > 23s! [test thread :1881]",i understand there is a watchdog but is there
> > > anyway i can feed the dog myself and let my thread have cpu as much as i
> > > want ?
> > 
> > Yowsers! Why would you want to do that? The whole idea of a watchdog is
> > to prevent threads hogging the CPU for a long time. Linux is a multi-user,
> > multi-process, pre-emptive operating system. It needs to share. :-)
> 
> Not true, Linux can take a cpu, remove itself from it, and run a single
> process if needed, just fine.  It's a great operating system for such a
> thing.

Hmm. Interesting. Looks like I've got more reading to do. :-)


Thanks,
Justin.

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Re: Question about watchdog

[Justin Skists]

> On 01 July 2018 at 13:44 bing zhu  wrote:
> 
> 
> Dear Sir/Ma'am
> Thank you for your time ,i'm a student new to linux kernel.at present ,i'd
> like to create a kernel thread
> say use kthread_create func ,my question is :how can i make this thread to
> run on a cpu and never get switched or scheduled , there is a
> while(1).structure in that thread i need it to do work . at present i
> comes with errors like "NMI watchdog: BUG: soft lockup - CPU#0 stuck for
> 23s! [test thread :1881]",i understand there is a watchdog but is there
> anyway i can feed the dog myself and let my thread have cpu as much as i
> want ?

Yowsers! Why would you want to do that? The whole idea of a watchdog is
to prevent threads hogging the CPU for a long time. Linux is a multi-user,
multi-process, pre-emptive operating system. It needs to share. :-)

If you really need a thread to hog the processor, indefinitely, then you're
probably using the wrong OS. Use the correct tool for the job. Or explore
"cpusets". Or maybe rebuild the kernel with soft watchdog turned off.


Justin.

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Re: policy on externs

[Justin Skists]

On Sat, Jun 02, 2018 at 07:33:46PM +0200, Greg KH wrote:
> On Sat, Jun 02, 2018 at 05:23:20PM +0100, Justin Skists wrote:
> > Hi,
> > 
> > What is the kernel policy on using "extern" to share variables between
> > source files in a module?
> > 
> > I've been looking at one subsystem in staging [that shares variables quite a
> > bit] to becoming familar with it, and seeing if I can help do some work on 
> > it
> > in my free time.
> > 
> > Personally I prefer to see them eradicated (they polute the namespace), and
> > store such variables in a context structure that is passed around. But I 
> > don't
> > see any reference about it in the coding style, and I am not one to
> > code-churn just because it's not my personal style! :)
> 
> context structures are almost always best, as they can be tied to the
> hardware device, not the module itself.  So yes, if they can be
> eradicated, please do so.

OK, Greg. I'll have another look at it, then.

> What driver are you looking at?

I have been looking at the speakup subsystem.


Thanks,
Justin.

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policy on externs

[Justin Skists]

Hi,

What is the kernel policy on using "extern" to share variables between
source files in a module?

I've been looking at one subsystem in staging [that shares variables quite a
bit] to becoming familar with it, and seeing if I can help do some work on it
in my free time.

Personally I prefer to see them eradicated (they polute the namespace), and
store such variables in a context structure that is passed around. But I don't
see any reference about it in the coding style, and I am not one to
code-churn just because it's not my personal style! :)


Thanks,
Justin

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Re: Eudyptula (Was: Kernelnewbies Digest, Vol 89, Issue 14)

[justin . skists]

> On 14 May 2018 at 08:43 Aleix Roca Nonell  wrote:
> 
> 
> On Wed, May 02, 2018 at 04:55:09PM +0200, Aleix Roca Nonell wrote:
> > On Thu, Apr 26, 2018 at 10:01:18PM +0100, justin.ski...@juzza.co.uk wrote:
> > > 
> > > > On 20 April 2018 at 07:28 Aleix Roca Nonell  
> > > > wrote:
> > > > 
> > > > I just wanted to ask the same question. I'm still doing the challenge
> > > > but it has been amost two months since I sent my last solution and
> > > > there has not been any answer yet (except the usual auto-response of
> > > > task received). Does somebody knows if it is still alive even for old
> > > > challengers?
> > > 
> > > I usually get a response when I'm about to go on holiday or AFK for a
> > > few days or so! :)
> > > 
> > > You need to remember that the maintainers who run the challenge are
> > > very busy people. The merge window for 4.17 was recently closed (and
> > > before that was the Spectre/Meltdown mess) so the maintainers are
> > > probably catching up on patches in their inbox.
> > > 
> > > Justin.
> > 
> > Oh! I understand. Thank you very much! :) In fact, I received a response
> > just a few days ago, so the challenge continues!
> > 
> > Thank you Justin! :)
> 
> Sorry I messed it up with mutt and sent the last reply only to Justin -_-'

:)

I was hoping there would be enough time for the reviewers to get to my last 
submission. Maybe changing my email address away from my gmail account had 
delayed matters.

Justin.

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Re: Compiler lacks asm go-to support

[Justin Skists]

On Tue, May 08, 2018 at 01:11:51AM +0530, Bhanusree Pola wrote:
> Hi all,
> 
> I have cloned kernel from 
> git clone -b staging-testing 
> git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging
> while configuring the following error is shown
> 
> arch/x86/Makefile:184: *** Compiler lacks asm-goto support..  Stop.
> 
> I have tried all possible debugging with the help of internet,but could
> not solve the problem.
> 
> Please help me in this regard

What compiler version are you using?

Justin

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Eudyptula (Was: Kernelnewbies Digest, Vol 89, Issue 14)

[justin . skists]

> On 20 April 2018 at 07:28 Aleix Roca Nonell  wrote:
> 
> I just wanted to ask the same question. I'm still doing the challenge
> but it has been amost two months since I sent my last solution and
> there has not been any answer yet (except the usual auto-response of
> task received). Does somebody knows if it is still alive even for old
> challengers?

I usually get a response when I'm about to go on holiday or AFK for a
few days or so! :)

You need to remember that the maintainers who run the challenge are
very busy people. The merge window for 4.17 was recently closed (and
before that was the Spectre/Meltdown mess) so the maintainers are
probably catching up on patches in their inbox.

Justin.

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Re: Eudyptual Challenge website and email service down?

[Justin Skists]

On 15 March 2018 12:26:40 GMT+00:00, Alexander Kapshuk 
 wrote:

>> Yes, the actual challenge has been put on hold and not taking in new
>> participants, but they have been still responding to the current
>> participants' emails.
>> This looks like their server could be down for maintenance, or
>something.
>
>Both the website as well as the email service seem to be up and running
>now.
>Thanks for fixing it.

That's good to know. There's still hope that the little penguin might find some 
time to review my last task submission. Perhaps after the 4.16 release...? :-)


Justin

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Re: QEMU environment setup for Linux Kernel

[Justin Skists]

On Wed, Mar 07, 2018 at 11:11:25PM +0530, Pintu Kumar wrote:
> So, I wanted to hear from other developer how they setup and use qemu
> environment.

I tend to use buildroot for my Linux hacking.
(https://buildroot.org/download.html)

(Or, sometimes Yocto when I'm feeling particularly brave)

Then it's a case of

$ cd buildroot
$ make list-defconfigs
$ make qemu_arm_versatile_defconfig 
 (or desired config)

$ make menuconfig

 [ select wanted target packages ]

$ make

view board/qemu/arm-versatile/readme.txt for running
instructions.

I've not compiled the Xorg in it recently, but there is the option for
graphical interface.

Hope that helps,
Justin.

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