Hello, Andrew. 2012/10/31 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>: > On Mon, 29 Oct 2012 04:12:53 +0900 > Joonsoo Kim <js1304@xxxxxxxxx> wrote: > >> The pool_lock protects the page_address_pool from concurrent access. >> But, access to the page_address_pool is already protected by kmap_lock. >> So remove it. > > Well, there's a set_page_address() call in mm/page_alloc.c which > doesn't have lock_kmap(). it doesn't *need* lock_kmap() because it's > init-time code and we're running single-threaded there. I hope! > > But this exception should be double-checked and mentioned in the > changelog, please. And it's a reason why we can't add > assert_spin_locked(&kmap_lock) to set_page_address(), which is > unfortunate. set_page_address() in mm/page_alloc.c is invoked only when WANT_PAGE_VIRTUAL is defined. And in this case, set_page_address()'s definition is not in highmem.c, but in include/linux/mm.h. So, we don't need to worry about set_page_address() call in mm/page_alloc.c > The irq-disabling in this code is odd. If ARCH_NEEDS_KMAP_HIGH_GET=n, > we didn't need irq-safe locking in set_page_address(). I guess we'll > need to retain it in page_address() - I expect some callers have IRQs > disabled. As Minchan described, if we don't disable irq when we take a lock for pas->lock, it would be deadlock with page_address(). -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>