On Wed, 25 Apr 2007, Christoph Lameter wrote: > On Wed, 25 Apr 2007, Hugh Dickins wrote: > > > SLUB gave me a NULL pointer dereference in slab_alloc(), in the > > slab_lock(page) of its "Current cpuslab is acceptable" block: cpu > > 1 had been looking at cpu_slab[2], which then went NULL beneath it. > > Since new_slab() may reenable interrupts and sleep (when __GFP_WAIT), > > we may get rescheduled on a different cpu: so need to reevaluate it. > > Right. local_irq_save does not switch off preemption as I thought.
Strange comment. Preemption is not possible while IRQs are disabled, but new_slab() rightly reenables them within itself in the __GFP_WAIT case, since it's going off to do a page allocation and may need to wait. (And actually, this kernel was a CONFIG_PREEMPT_NONE=y one.) > > Acked-by: Christoph Lameter <[EMAIL PROTECTED]> Thanks, Hugh - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
