Re: [Xen-devel] atomic counters larger than 24 bits?

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 26/03/2009 23:26, "Samuel Thibault" <samuel.thibault@xxxxxxxxxxxx> wrote:

> Dan Magenheimer, le Thu 26 Mar 2009 19:38:13 +0000, a écrit :
>> In tmem, I have some counters that I need to keep coherent,
>> preferably without a lock, so I'm using atomic_inc/dec etc.
>> However the comments in include/asm-x86/atomic.h say repeatedly
>> that the "useful range of an atomic_t is only 24 bits".
> 
> IIRC the historical reason for this is that some Linux architectures
> weren't providing more.  The x86 implementation does support signed 32
> bits. I believe the ia64 implementation does too.

Yes, I'll fix the x86/atomic.h comments. Our atomic_t type is signed and at
least 32 bits. I don't see we'll ever port to an architecture without
cmpxchg or similar to easily support 'full width' atomic_t.

 -- Keir



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel