On Thu, 8 Feb 2007, Nick Piggin wrote: > Still no independent confirmation as to whether this is a problem or not.
I'm trying to convince myself none of your patch is necessary. Probably shall fail. But how come we've survived for years with such an issue? > Updated some comments, added diffstats to patches, don't use > __SetPageUptodate as an internal page-flags.h private function. Depressed by profusion of PageUptodate_UpperAndlowercasevariants. Those rmbs, you really only want them when it says "yes", don't you? > > I would like to eventually get an ack from Hugh regarding the anon memory > and especially swap side of the equation, Plea noted. I'm pondering. "Eventually" indeed. OTOH I expect you're right to criticize anon/swap PageUptodate being set where it was needed to get by, rather than where it was natural to do so. > and a glance from whoever put the > smp_wmb()s into the copy functions (Was it Ben H or Anton maybe?) From: Linus Torvalds <[EMAIL PROTECTED]> Date: Thu, 14 Oct 2004 04:00:06 +0000 (-0700) Subject: Fix threaded user page write memory ordering X-Git-Tag: v2.6.9-final~3 X-Git-Url: http://127.0.0.1:1234/?p=.git;a=commitdiff_plain;h=538ce05c0ef4055cf29a92a4abcdf139d180a0f9;hp=8c225dbc5a7b13801a8254aae0ccebab8e4bece7 Fix threaded user page write memory ordering Make sure we order the writes to a newly created page with the page table update that potentially exposes the page to another CPU. This is a no-op on any architecture where getting the page table spinlock will already do the ordering (notably x86), but other architectures can care. --- diff --git a/include/linux/highmem.h b/include/linux/highmem.h index 232d8fd..7153aef 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -40,6 +40,8 @@ static inline void clear_user_highpage(s void *addr = kmap_atomic(page, KM_USER0); clear_user_page(addr, vaddr, page); kunmap_atomic(addr, KM_USER0); + /* Make sure this page is cleared on other CPU's too before using it */ + smp_wmb(); } static inline void clear_highpage(struct page *page) @@ -73,6 +75,8 @@ static inline void copy_user_highpage(st copy_user_page(vto, vfrom, vaddr, to); kunmap_atomic(vfrom, KM_USER0); kunmap_atomic(vto, KM_USER1); + /* Make sure this page is cleared on other CPU's too before using it */ + smp_wmb(); } static inline void copy_highpage(struct page *to, struct page *from) - 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/
