From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id 96A226B004F for ; Fri, 23 Jan 2009 11:37:58 -0500 (EST) Subject: [PATCH] x86,mm: fix pte_free() From: Peter Zijlstra Content-Type: text/plain Date: Fri, 23 Jan 2009 17:37:49 +0100 Message-Id: <1232728669.4826.143.camel@laptop> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Linus Torvalds , Nick Piggin , Hugh Dickins , Thomas Gleixner , Ingo Molnar , Andrew Morton Cc: L-K , linux-mm , David Howells List-ID: On -rt we were seeing spurious bad page states like: Bad page state in process 'firefox' page:c1bc2380 flags:0x40000000 mapping:c1bc2390 mapcount:0 count:0 Trying to fix it up, but a reboot is needed Backtrace: Pid: 503, comm: firefox Not tainted 2.6.26.8-rt13 #3 [] ? printk+0x14/0x19 [] bad_page+0x4e/0x79 [] free_hot_cold_page+0x5b/0x1d3 [] free_hot_page+0xf/0x11 [] __free_pages+0x20/0x2b [] __pte_alloc+0x87/0x91 [] handle_mm_fault+0xe4/0x733 [] ? rt_mutex_down_read_trylock+0x57/0x63 [] ? rt_mutex_down_read_trylock+0x57/0x63 [] do_page_fault+0x36f/0x88a This is the case where a concurrent fault already installed the PTE and we get to free the newly allocated one. This is due to pgtable_page_ctor() doing the spin_lock_init(&page->ptl) which is overlaid with the {private, mapping} struct. union { struct { unsigned long private; struct address_space *mapping; }; #if NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS spinlock_t ptl; #endif struct kmem_cache *slab; struct page *first_page; }; Normally the spinlock is small enough to not stomp on page->mapping, but PREEMPT_RT=y has huge 'spin'locks. But lockdep kernels should also be able to trigger this splat, as the lock tracking code grows the spinlock to cover page->mapping. The obvious fix is calling pgtable_page_dtor() like the regular pte free path __pte_free_tlb() does. It seems all architectures except x86 and nm10300 already do this, and nm10300 doesn't seem to use pgtable_page_ctor(), which suggests it doesn't do SMP or simply doesnt do MMU at all or something. Signed-off-by: Peter Zijlstra CC: stable@kernel.org --- arch/x86/include/asm/pgalloc.h | 1 + 1 files changed, 1 insertions(+), 0 deletions(-) diff --git a/arch/x86/include/asm/pgalloc.h b/arch/x86/include/asm/pgalloc.h index cb7c151..b99023c 100644 --- a/arch/x86/include/asm/pgalloc.h +++ b/arch/x86/include/asm/pgalloc.h @@ -42,6 +42,7 @@ static inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte) static inline void pte_free(struct mm_struct *mm, struct page *pte) { + pgtable_page_dtor(); __free_page(pte); } -- 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