threads

threads

[M.Kiran Babu]

 sir,
i got some doubts in kernel
programming. i am using linux 6.1 version. i want to use threads in
kernel.is it possible to use pthreads in kernel. there is one more
function kernel_thread. can i use
that function. if i use that function how to get synchonization. inmany
files it was used. but everywhere lock_kernel() and unlock_kernel()
functions are being used. if we use that commands the whole kernel gets
locked. is there any other mechanisms. or can i use that methods only. if
i can use these methods what is the syntax of kernel_thread function. the
arguments that are passing to these function are 3. i dont know what are
those three. please  tell me.
				




                                               
                        
               




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Re: threads

[Matti Aarnio]

On Fri, Nov 10, 2000 at 08:33:29PM +0530, M.Kiran Babu wrote:
>  sir,
> i got some doubts in kernel
> programming. i am using linux 6.1 version. i want to use threads in

	Linux kernel versions are now running up to 2.4.0*, what is
	that 6.1 ?  Some distribution ?  Which ?
	Which kernel version you are referring into ?

> kernel.is it possible to use pthreads in kernel. there is one more
                               ^^^^^^^^^^^^^^^^^^   NO.
> function kernel_thread.
> can i use that function.

	#include <asm/processor.h>

	extern pid_t kernel_thread(int (*fn)(void *), void * arg,
				   unsigned long flags);

> if i use that function how to get synchonization.

	With mutexes, waitqueues, or spinlocks.
	All kernel facilities.

> inmany files it was used. but everywhere lock_kernel() and unlock_kernel()
> functions are being used. if we use that commands the whole kernel gets
> locked.

	Really ?  Who says you need to   lock_kernel()  for starting
	a kernel thread ?

> is there any other mechanisms. or can i use that methods only.
> if i can use these methods what is the syntax of kernel_thread function.
> the arguments that are passing to these function are 3.
> i dont know what are those three. please tell me.

	Pick 2.4.0 sources, open them up.

	Then do:  "make psdocs" or "make pdfdocs" or "make htmldocs"
	and you get up documents from within the system into your
	source location Documentation/DocBook/  subdirectory.

	You propably want to study  kernel-hacking,  kernel-locking,
	and  kernel-api   documents.

	(Your system needs to have DocBook, related SGML tools, and
	 (for PS/PDF) (La)TeX subsystem.)

/Matti Aarnio
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Re: threads

[Reto Baettig]

lock_kernel is a special case and will not block when you call it in
order to create a new kernel thread. Look at the implementation of
lock_kernel if you have any doubts (this is true for the 2.2 kernels. I
don't know it by heart for the 2.4 kernel). 

	Reto

"M.Kiran Babu" wrote:
> 
>  sir,
> i got some doubts in kernel
> programming. i am using linux 6.1 version. i want to use threads in
> kernel.is it possible to use pthreads in kernel. there is one more
> function kernel_thread. can i use
> that function. if i use that function how to get synchonization. inmany
> files it was used. but everywhere lock_kernel() and unlock_kernel()
> functions are being used. if we use that commands the whole kernel gets
> locked. is there any other mechanisms. or can i use that methods only. if
> i can use these methods what is the syntax of kernel_thread function. the
> arguments that are passing to these function are 3. i dont know what are
> those three. please  tell me.
> 
> 
> 
> 
> 
> 
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> Please read the FAQ at http://www.tux.org/lkml/
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Re: threads

[J . A . Magallon]

On 03.07 Ying Chen wrote:
> 2. We ran multi-threaded application using Linux pthread library on 2-way 
> SMP and UP intel platforms (with both 2.2 and 2.4 kernels). We see 
> significant increase in context switching when moving from UP to SMP, and 
> high CPU usage with no performance gain in turns of actual work being done 
> when moving to SMP, despite the fact the benchmark we are running is 
> CPU-bound. The kernel profiler indicates that the a lot of kernel CPU ticks 
> went to scheduling and signaling overheads. Has anyone seen something like 
> this before with pthread applications running on SMP platforms? Any 
> suggestions or pointers on this subject?
> 

Too much contention ? How frequently do you create and destroy threads ?
How much frequently do they access shared-writable-data ?
How do you protect them ?

It seems like your system spents more time creating and killing threads
that doing real work.

-- 
J.A. Magallon                                                      $> cd pub
mailto:jamagallon@able.es                                          $> more beer

Linux werewolf 2.4.2-ac13 #3 SMP Wed Mar 7 00:09:17 CET 2001 i686