On Tue, 2005-02-01 at 17:20 -0800, Christoph Lameter wrote: > On Wed, 2 Feb 2005, Nick Piggin wrote: > > > > The unmapping in rmap.c would change the pte. This would be discovered > > > after acquiring the spinlock later in do_wp_page. Which would then lead to > > > the operation being abandoned. > > Oh yes, but suppose your page_cache_get is happening at the same time > > as free_pages_check, after the page gets freed by the scanner? I can't > > actually think of anything that would cause a real problem (ie. not a > > debug check), off the top of my head. But can you say there _isn't_ > > anything? > > > > Regardless, it seems pretty dirty to me. But could possibly be made > > workable, of course. > > Would it make you feel better if we would move the spin_unlock back to the > prior position? This would ensure that the fallback case is exactly the > same. >
Well yeah, but the interesting case is when that isn't a lock ;) I'm not saying what you've got is no good. I'm sure it would be fine for testing. And if it happens that we can do the "page_count doesn't mean anything after it has reached zero and been freed. Nor will it necessarily be zero when a new page is allocated" thing without many problems, then this may be a fine way to do it. I was just pointing out this could be a problem without putting a lot of thought into it... Find local movie times and trailers on Yahoo! Movies. http://au.movies.yahoo.com - 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/
