Re: [PATCH 2/5] atomic: introduce atomic_inc_not_zero

[Dipankar Sarma <dipankar@in.ibm.com>]

On Sat, Sep 17, 2005 at 03:15:29AM +0200, Roman Zippel wrote:
> Hi,
> 
> On Thu, 15 Sep 2005, Nick Piggin wrote:
> 
> > Roman: any ideas about what you would prefer? You'll notice
> > atomic_inc_not_zero replaces rcuref_inc_lf, which is used several times
> > in the VFS.
> 
> In the larger picture I'm not completely happy with these scalibilty 
> patches, as they add extra overhead at the lower end. On a UP system in 
> general nothing beats:
> 
> 	spin_lock();
> 	if (*ptr)
> 		ptr += 1;
> 	spin_unlock();
> 
> The main problem is here that the atomic functions are used in two basic 
> situation:

Are you talking about the lock-free fdtable patches ? They don't replace
non-atomic locked critical sections by atomic operations. Reference counting
is already there to extend the life of objects beyond locked critical
setions.

Thanks
Dipankar