On 11/5/12 4:26 PM, Andrew Morton wrote: > > OK, so it seems that those drivers have never been tested on a > CONFIG_NUMA kernel. whee. > > So we have a large amount of code here which ostensibly supports > dev==NULL but which has not been well tested. Take a look at > dma_alloc_coherent(), dma_free_coherent() - are they safe? Unobvious. It's probably ok to call dma_alloc_coherent()/dma_free_coherent() with a NULL dev. Quite a few drivers do that. > dmam_pool_destroy() will clearly cause an oops: > > devres_destroy() > ->devres_remove() > ->spin_lock_irqsave(&dev->devres_lock, flags); Not sure if I missed anything, but I haven't found any use of dmam_pool_destroy() in the tree.. > I'm thinking we should disallow dev==NULL. We have a lot of code in > mm/dmapool.c which _attempts_ to support this case, but is largely > untested and obviously isn't working. I don't think it's a good idea > to try to fix up and then support this case on behalf of a handful of > scruffy drivers. It would be better to fix the drivers, then simplify > the core code. drivers/usb/gadget/amd5536udc.c can probably use > dev->gadget.dev and drivers/net/wan/ixp4xx_hss.c can probably use > port->netdev->dev, etc. After more search I've still only found 4 files that invoke dma_pool_create() with a NULL dev. arch/arm/mach-s3c64xx/dma.c drivers/usb/gadget/amd5536udc.c drivers/net/wan/ixp4xx_hss.c drivers/net/ethernet/xscale/ixp4xx_eth.c So, yeah, we could fix those drivers instead, such as adding "WARN_ON_ONCE(dev == NULL)" as you suggested. - xi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>