On Fri, Apr 25, 2008 at 3:42 PM, Philippe Gerum <[EMAIL PROTECTED]> wrote:
> Gilles Chanteperdrix wrote:
> > On Fri, Apr 25, 2008 at 9:48 AM, Philippe Gerum <[EMAIL PROTECTED]> wrote:
> >> Gilles Chanteperdrix wrote:
> >> > This patch implements the _read, _set, and _cmpxchg operations on
> >> > and atomic_ptr_t in user-space in include/asm-generic/atomic.h which
> should be
> >> > included at the end of include/asm-*/atomic.h after the definition of
> the same
> >> > operations for the atomic_t type and atomic64_t type on 64 bits
> >> >
> >> > These operations are the basic operations used by user-space mutexes.
> Maybe we
> >> > should add the xnarch_ prefix ?
> >> >
> >> Yes, but more generally, we should rework this to fit the existing atomic
> >> support in include/asm-*/atomic.h, so that we don't end up with sideways
> to what
> >> has been already designed to support set, get, xchg and the like, in
> both kernel
> >> and userland context.
> > That is not exactly sideways... Linux include/asm-generic/atomic.h
> > defines operations for atomic_long_t. This file adds two things:
> > - support for atomic_long_t in user-space (where we can not include
> > linux include/asm-generic/atomic.h)
> > - support for a new type atomic_ptr_t both to kernel-space and
> > user-space, the aim is to avoid all the casts that would take place if
> > we wanted to use atomic_long_t to store pointers.
> > However for this file to work, it has to be included by asm-*/atomic.h
> > after the definition of atomic_t (and atomic64_t on 64 bits
> > platforms). So linux includes asm-generic/atomic.h at the end of
> > asm/atomic.h, I simply reproduced this scheme with Xenomai
> > include/asm-*/atomic.h.
> Focusing on user-space: 1) xnarch_atomic_xchg is meant to work on long
> types; 2)
> set, get routines are not defined in that scope. If the purpose is to define
> integer-type ops to handle pointer-type data atomically (i.e. intptr_t),
> then I
> would rather check whether we actually need non-long support at all in
> user-space. In case we don't, I would simply reply on the existing
> implementation of asm-*/atomic.h + the set / get extensions you provide.
I use both atomic_t and atomic_ptr_t for the implementation of
user-space mutexes. The problem is that I am constrained by the size
of pthread_mutex_t, so the "control block read-write locks"
implementation use atomic_t.
Xenomai-core mailing list