On Mon, 2010-05-10 at 19:29 +0900, Paul Mundt wrote: > On Mon, May 10, 2010 at 11:16:47AM +0100, Catalin Marinas wrote: > > In most situations, just doing flushing in set_pte_at() would suffice > > and flush_dcache_page() can be ignored. There are two situations where I > > still see flush_dcache_page() useful: > > > > 1. SMP systems where the cache maintenance operations aren't > > automatically broadcast in hardware > > 2. The kernel modifies a page cache page that is already mapped in > > user space > > > > (1) can be worked around on some architectures (though not sure about > > all of them). > > > > Is (2) a valid scenario? > > > get_user_pages() ? Actually, no, not really. get_user_pages() is preparing the pages for DMA (so it pins and possibly flushes them to make the underlying physical page in the page cache clean). This means it gathers the physical pages into a scatter gather list. It actually assumes the kernel *won't* be touching them (without using kmap), so it doesn't give the pages an in-kernel mapping. James -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
