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.

-- 
Philippe.

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