Messages in this thread | | | Date | Tue, 20 Nov 2007 16:43:20 -0500 | From | Mathieu Desnoyers <> | Subject | Re: [rfc 04/45] cpu alloc: Use in SLUB |
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* 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/
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