On Tue, 8 May 2012, Eric Dumazet wrote: > On Tue, 2012-05-08 at 11:55 -0700, Pravin B Shelar wrote: > > Transparent huge pages can change page->flags (PG_compound_lock) > > without taking Slab lock. So sl[auo]b need to use atomic bit > > operation while changing page->flags. > > Specificly this patch fixes race between compound_unlock and slab > > functions which does page-flags update. This can occur when > > get_page/put_page is called on page from slab object. > > > But should get_page()/put_page() be called on a page own by slub ? Can occur in slab allocators if the slab memory is used for DMA. I dont like the performance impact of the atomics. In particular slab_unlock() in slub is or used to be a hot path item. It is still hot on arches that do not support this_cpu_cmpxchg_double. With the cmpxchg_double only the debug mode is affected. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>