Gilles Chanteperdrix wrote: > On Fri, Apr 25, 2008 at 4:01 PM, Philippe Gerum <[EMAIL PROTECTED]> wrote: >> Gilles Chanteperdrix wrote: >> > 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 >> atomic_long_t >> >> >> > 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 >> platforms. >> >> >> > >> >> >> > 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. >> > >> >> Ok, makes sense. Let's just fix the namespace then, so that we don't get the >> feeling of having duplicate sets of operations. > > That said, there is just enough room for replacing the atomic_t with > an atomic_long_t. So, we can make xnarch_atomic_t a long type. Have > you anything agains making an xnarch_atomic_ptr_t ? >
No objection, just let us call it xnarch_atomic_intptr_t to ANSIfy this a bit more, and clearly state that we need this type to hold a pointer into an integer value, and operate atomically on it. -- Philippe. _______________________________________________ Xenomai-core mailing list Xenomai-core@gna.org https://mail.gna.org/listinfo/xenomai-core
