On Mon 25-10-10 15:49:33, Wu Fengguang wrote: > On Mon, Oct 25, 2010 at 02:37:26PM +0800, KAMEZAWA Hiroyuki wrote: > > I wonder this should be for stable tree...but want to hear opinions before. > > == > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > > > > page_order() is called by memory hotplug's user interface to check > > the section is removable or not. (is_mem_section_removable()) > > > > It calls page_order() withoug holding zone->lock. > > So, even if the caller does > > > > if (PageBuddy(page)) > > ret = page_order(page) ... > > The caller may hit BUG_ON(). > > > > For fixing this, there are 2 choices. > > 1. add zone->lock. > > 2. remove BUG_ON(). > > One more alternative might be to introduce a private > maybe_page_order() for is_mem_section_removable(). Not a big deal. I guess this is not necessary as all page_order callers check PageBuddy anyway AFAICS. > > > is_mem_section_removable() is used for some "advice" and doesn't need > > to be 100% accurate. This is_removable() can be called via user program.. > > We don't want to take this important lock for long by user's request. > > So, this patch removes BUG_ON(). > > Acked-by: Wu Fengguang <fengguang.wu@xxxxxxxxx> Yes, the change looks good. -- Michal Hocko L3 team SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>