> Date: Sat, 31 Dec 2011 16:32:20 +0100
> From: gilles.chanteperd...@xenomai.org
> To: jan0...@hotmail.de
> CC: xenomai-core@gna.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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