lkml.org 
[lkml]   [2007]   [Nov]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [rfc 04/45] cpu alloc: Use in SLUB
* Christoph Lameter (clameter@sgi.com) wrote:
> On Tue, 20 Nov 2007, Mathieu Desnoyers wrote:
>
> > > > > - __slab_free(s, page, x, addr, c->offset);
> > > > > + if (unlikely(page != __CPU_READ(c->page) ||
> > > > > + __CPU_READ(c->node) < 0)) {
> > > > > + __slab_free(s, page, x, addr, __CPU_READ(c->offset));
> > > >
> > > > And same question as above : what happens if we fail after executing the
> > > > __slab_free.. is it valid to do it twice ?
> > >
> > > __slab_free is always successful and will never cause a repeat of the
> > > loop.
> >
> > Then what happens if we are migrated between the end of __slab_free and
> > the CPU_CMPXCHG ? The cmpxchg would fail, and the __slab_free will be
> > done twice ?
>
> Look at the control flow. The __slab_free can never be done twice.
>
> {
> freelist = __CPU_READ(c->freelist);
> barrier();
> if (unlikely(page != __CPU_READ(c->page) ||
> __CPU_READ(c->node) < 0)) {
> __slab_free(s, page, x, addr);
> break;
> ^^^^^^^ no redo of the loop possible.
>
> }
> set_freepointer(s, object, freelist);
> } while (CPU_CMPXCHG(c->freelist, freelist, object) != freelist);
>

oops, I should remember not to review code before my first coffee in the
morning ;)

--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-11-20 22:51    [W:0.136 / U:0.620 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site