[Xenomai-core] user and kernel space

[Xenomai-core] user and kernel space

[Jan-Erik Lange]

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Hello,
 
I have a question concerning user space and kernel space. I'm dealing with the native API and I read, that this API provides the same funtkions for both kernel and user space. 
 
When looking at the sourcecode of buffer.h for example, there I find a section called public interface. When looking at the function rt_buffer_create(); for example, how does the Implementation von this function in userspace differs to the implementation for this function kernel space? Or is it the same implementation for user and kernel space.
 
Best regards
 
Jan 		 	   		  

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Re: [Xenomai-core] user and kernel space

[Gilles Chanteperdrix]

On 12/31/2011 12:18 PM, Jan-Erik Lange wrote:
> 
> Hello,
> 
> I have a question concerning user space and kernel space. I'm dealing
> with the native API and I read, that this API provides the same
> funtkions for both kernel and user space.
> 
> When looking at the sourcecode of buffer.h for example, there I find
> a section called public interface. When looking at the function
> rt_buffer_create(); for example, how does the Implementation von this
> function in userspace differs to the implementation for this function
> kernel space? Or is it the same implementation for user and kernel
> space.

For most services such as buffer services, user functions emit system
calls which implementation in kernel-space use the corresponding kernel
service.

There are some exceptions such as mutexes implementation where we try
hard to avoid system calls and so provide both a user-space
implementation and a kernel-space implementation.

Another exception is the __xn_rdtsc() function, which relies on most
platforms on the same mechanism in user and kernel-space to access the
machine high resolution counter, and so has an identical implementation.


-- 
                                                                Gilles.

Re: [Xenomai-core] user and kernel space

[Jan-Erik Lange]

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> Date: Sat, 31 Dec 2011 16:32:20 +0100
> From: gilles.chanteperdrix@xenomai.org
> To: jan0385@domain.hid
> CC: xenomai@xenomai.org
> Subject: Re: [Xenomai-core] user and kernel space
> 
> On 12/31/2011 12:18 PM, Jan-Erik Lange wrote:
> > 
> > Hello,
> > 
> > I have a question concerning user space and kernel space. I'm dealing
> > with the native API and I read, that this API provides the same
> > funtkions for both kernel and user space.
> > 
> > When looking at the sourcecode of buffer.h for example, there I find
> > a section called public interface. When looking at the function
> > rt_buffer_create(); for example, how does the Implementation von this
> > function in userspace differs to the implementation for this function
> > kernel space? Or is it the same implementation for user and kernel
> > space.
> 
> For most services such as buffer services, user functions emit system
> calls which implementation in kernel-space use the corresponding kernel
> service.
> 
> There are some exceptions such as mutexes implementation where we try
> hard to avoid system calls and so provide both a user-space
> implementation and a kernel-space implementation.
 
 
Ok, but the names of the API function are the same for user and kernel space. How is it realized to take the implementation A for kernel space and the implementation B for userspace? Is this realzied in the linking process?

> 
> Another exception is the __xn_rdtsc() function, which relies on most
> platforms on the same mechanism in user and kernel-space to access the
> machine high resolution counter, and so has an identical implementation.
> 
> 
 
> -- 
> Gilles.
 		 	   		  

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Re: [Xenomai-core] user and kernel space

[Gilles Chanteperdrix]

On 01/01/2012 01:56 PM, Jan-Erik Lange wrote:
> 
> 
> 
> 
>> Date: Sat, 31 Dec 2011 16:32:20 +0100 From:
>> gilles.chanteperdrix@xenomai.org To: jan0385@domain.hid CC:
>> xenomai@xenomai.org Subject: Re: [Xenomai-core] user and kernel
>> space
>> 
>> On 12/31/2011 12:18 PM, Jan-Erik Lange wrote:
>>> 
>>> Hello,
>>> 
>>> I have a question concerning user space and kernel space. I'm
>>> dealing with the native API and I read, that this API provides
>>> the same funtkions for both kernel and user space.
>>> 
>>> When looking at the sourcecode of buffer.h for example, there I
>>> find a section called public interface. When looking at the
>>> function rt_buffer_create(); for example, how does the
>>> Implementation von this function in userspace differs to the
>>> implementation for this function kernel space? Or is it the same
>>> implementation for user and kernel space.
>> 
>> For most services such as buffer services, user functions emit
>> system calls which implementation in kernel-space use the
>> corresponding kernel service.
>> 
>> There are some exceptions such as mutexes implementation where we
>> try hard to avoid system calls and so provide both a user-space 
>> implementation and a kernel-space implementation.
> 
> 
> Ok, but the names of the API function are the same for user and
> kernel space. How is it realized to take the implementation A for
> kernel space and the implementation B for userspace? Is this realzied
> in the linking process?

Yes, kernel and user-space are separated execution space, there is no
possible confusion.

-- 
                                                                Gilles.