From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 5 May 2008 17:37:30 +0100 (BST) From: Hugh Dickins Subject: Re: [patch 2/2] fix SMP data race in pagetable setup vs walking In-Reply-To: Message-ID: References: <20080505112021.GC5018@wotan.suse.de> <20080505121240.GD5018@wotan.suse.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Linus Torvalds Cc: Nick Piggin , linux-arch@vger.kernel.org, Linux Memory Management List , Paul McKenney List-ID: On Mon, 5 May 2008, Linus Torvalds wrote: > On Mon, 5 May 2008, Nick Piggin wrote: > > > > Index: linux-2.6/include/asm-x86/pgtable_32.h > > =================================================================== > > --- linux-2.6.orig/include/asm-x86/pgtable_32.h > > +++ linux-2.6/include/asm-x86/pgtable_32.h > > @@ -133,7 +133,12 @@ extern int pmd_bad(pmd_t pmd); > > * pgd_offset() returns a (pgd_t *) > > * pgd_index() is used get the offset into the pgd page's array of pgd_t's; > > */ > > -#define pgd_offset(mm, address) ((mm)->pgd + pgd_index((address))) > > +#define pgd_offset(mm, address) \ > > +({ \ > > + pgd_t *ret = ((mm)->pgd + pgd_index((address))); \ > > + smp_read_barrier_depends(); /* see mm/memory.c:__pte_alloc */ \ > > + ret; \ > > +}) > > Is there some fundamental reason this needs to be a macro? > > It is really ugly, and it would be much nicer to make this an inline > function if at all possible. > > Yeah, maybe it requires some more #include's, but .. My recollection is that it gets difficult once you reach pte_offset_map(), which involved kmap_atomic() (now kmap_atomic_pte()), which gets twisty. Or perhaps my problems arose from doing pte_offset_map_lock() in the generic linux/mm.h: harder to herd that safely through the different arch builds. Hugh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org