On 2024/9/19 17:42, Jesper Dangaard Brouer wrote: > > On 18/09/2024 19.06, Ilias Apalodimas wrote: >>> In order not to do the dma unmmapping after driver has already >>> unbound and stall the unloading of the networking driver, add >>> the pool->items array to record all the pages including the ones >>> which are handed over to network stack, so the page_pool can >>> do the dma unmmapping for those pages when page_pool_destroy() >>> is called. >> >> So, I was thinking of a very similar idea. But what do you mean by >> "all"? The pages that are still in caches (slow or fast) of the pool >> will be unmapped during page_pool_destroy(). > > I really dislike this idea of having to keep track of all outstanding pages. > > I liked Jakub's idea of keeping the netdev around for longer. > > This is all related to destroying the struct device that have points to > the DMA engine, right? Yes, the problem seems to be that when device_del() is called, there is no guarantee hw behind the 'struct device ' will be usable even if we call get_device() on it. > > Why don't we add an API that allow netdev to "give" struct device to > page_pool. And then the page_poll will take over when we can safely > free the stuct device? By 'allow netdev to "give" struct device to page_pool', does it mean page_pool become the driver for the device? If yes, it seems that is similar to jakub's idea, as both seems to stall the calling of device_del() by not returning when the driver unloading. If no, it seems that the problem is still existed when the driver for the device has unbound after device_del() is called. > > --Jesper
