On Mon, 10 Nov 2014, Andrey Ryabinin wrote: > After enabling alignment checks in UBSan I've noticed a lot of > reports like this: > > UBSan: Undefined behaviour in ../kernel/irq/chip.c:195:14 > member access within misaligned address ffff88003e80d6f8 > for type 'struct irq_desc' which requires 16 byte alignment > > struct irq_desc declared with ____cacheline_internodealigned_in_smp > attribute. However in some cases it allocated dynamically via kmalloc(). > In general case kmalloc() guaranties only sizeof(void *) alignment. > We should use a separate slab cache to make struct irq_desc > properly aligned on SMP configuration. > > This also could slightly reduce memory usage on some configurations. > E.g. in my setup sizeof(struct irq_desc) == 320. Which means that > kmalloc-512 will be used for allocating irg_desc via kmalloc(). > In that case using separate slab cache will save us 192 bytes per > each irq_desc. > > Note: UBSan reports says that 'struct irq_desc' requires 16 byte alignment. > It's wrong, in my setup it should be 64 bytes. This looks like a gcc bug, > but it doesn't change the fact that irq_desc is misaligned. > > Signed-off-by: Andrey Ryabinin <a.ryabi...@samsung.com>
I think this is just fine, I would just prefer that you do the memset() explicitly rather than introduce the new slab function for such a specialized purpose (unless there's other examples in the kernel where this would be useful). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
