From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755575Ab1BOTH5 (ORCPT ); Tue, 15 Feb 2011 14:07:57 -0500 Received: from mx1.redhat.com ([209.132.183.28]:15316 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751598Ab1BOTHz (ORCPT ); Tue, 15 Feb 2011 14:07:55 -0500 Date: Tue, 15 Feb 2011 20:07:10 +0100 From: Andrea Arcangeli To: Jeremy Fitzhardinge Cc: "H. Peter Anvin" , the arch/x86 maintainers , "Xen-devel@lists.xensource.com" , Linux Kernel Mailing List , Ian Campbell , Jan Beulich , Larry Woodman , Andrew Morton , Andi Kleen , Johannes Weiner , Hugh Dickins , Rik van Riel Subject: [PATCH] fix pgd_lock deadlock Message-ID: <20110215190710.GL5935@random.random> References: <4CB76E8B.2090309@goop.org> <4CC0AB73.8060609@goop.org> <20110203024838.GI5843@random.random> <4D4B1392.5090603@goop.org> <20110204012109.GP5843@random.random> <4D4C6F45.6010204@goop.org> <20110207232045.GJ3347@random.random> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110207232045.GJ3347@random.random> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Without this patch we can deadlock in the page_table_lock with NR_CPUS < 4 or THP on, with this patch we hopefully won't deadlock in the pgd_lock (if taken from irq). I can't see anything taking it from irq (maybe aio? to check I also tried the libaio testuite with no apparent VM_BUG_ON triggering), so unless somebody sees it, I think we should apply it. I've been running for a while with this patch applied without apparent problems. Other archs may follow suit if it's proven that there's nothing taking the pgd_lock from irq. === Subject: fix pgd_lock deadlock From: Andrea Arcangeli It's forbidden to take the page_table_lock with the irq disabled or if there's contention the IPIs (for tlb flushes) sent with the page_table_lock held will never run leading to a deadlock. Apparently nobody takes the pgd_lock from irq so the _irqsave can be removed. Signed-off-by: Andrea Arcangeli --- arch/x86/mm/fault.c | 8 ++++---- arch/x86/mm/init_64.c | 7 ++++--- arch/x86/mm/pageattr.c | 21 +++++++++++---------- arch/x86/mm/pgtable.c | 13 ++++++------- arch/x86/xen/mmu.c | 10 ++++------ 5 files changed, 29 insertions(+), 30 deletions(-) --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -229,15 +229,15 @@ void vmalloc_sync_all(void) for (address = VMALLOC_START & PMD_MASK; address >= TASK_SIZE && address < FIXADDR_TOP; address += PMD_SIZE) { - - unsigned long flags; struct page *page; - spin_lock_irqsave(&pgd_lock, flags); + VM_BUG_ON(in_interrupt()); + spin_lock(&pgd_lock); list_for_each_entry(page, &pgd_list, lru) { spinlock_t *pgt_lock; pmd_t *ret; + /* the pgt_lock only for Xen */ pgt_lock = &pgd_page_get_mm(page)->page_table_lock; spin_lock(pgt_lock); @@ -247,7 +247,7 @@ void vmalloc_sync_all(void) if (!ret) break; } - spin_unlock_irqrestore(&pgd_lock, flags); + spin_unlock(&pgd_lock); } } --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -105,18 +105,19 @@ void sync_global_pgds(unsigned long star for (address = start; address <= end; address += PGDIR_SIZE) { const pgd_t *pgd_ref = pgd_offset_k(address); - unsigned long flags; struct page *page; if (pgd_none(*pgd_ref)) continue; - spin_lock_irqsave(&pgd_lock, flags); + VM_BUG_ON(in_interrupt()); + spin_lock(&pgd_lock); list_for_each_entry(page, &pgd_list, lru) { pgd_t *pgd; spinlock_t *pgt_lock; pgd = (pgd_t *)page_address(page) + pgd_index(address); + /* the pgt_lock only for Xen */ pgt_lock = &pgd_page_get_mm(page)->page_table_lock; spin_lock(pgt_lock); @@ -128,7 +129,7 @@ void sync_global_pgds(unsigned long star spin_unlock(pgt_lock); } - spin_unlock_irqrestore(&pgd_lock, flags); + spin_unlock(&pgd_lock); } } --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -57,12 +57,11 @@ static unsigned long direct_pages_count[ void update_page_count(int level, unsigned long pages) { - unsigned long flags; - /* Protect against CPA */ - spin_lock_irqsave(&pgd_lock, flags); + VM_BUG_ON(in_interrupt()); + spin_lock(&pgd_lock); direct_pages_count[level] += pages; - spin_unlock_irqrestore(&pgd_lock, flags); + spin_unlock(&pgd_lock); } static void split_page_count(int level) @@ -394,7 +393,7 @@ static int try_preserve_large_page(pte_t *kpte, unsigned long address, struct cpa_data *cpa) { - unsigned long nextpage_addr, numpages, pmask, psize, flags, addr, pfn; + unsigned long nextpage_addr, numpages, pmask, psize, addr, pfn; pte_t new_pte, old_pte, *tmp; pgprot_t old_prot, new_prot, req_prot; int i, do_split = 1; @@ -403,7 +402,8 @@ try_preserve_large_page(pte_t *kpte, uns if (cpa->force_split) return 1; - spin_lock_irqsave(&pgd_lock, flags); + VM_BUG_ON(in_interrupt()); + spin_lock(&pgd_lock); /* * Check for races, another CPU might have split this page * up already: @@ -498,14 +498,14 @@ try_preserve_large_page(pte_t *kpte, uns } out_unlock: - spin_unlock_irqrestore(&pgd_lock, flags); + spin_unlock(&pgd_lock); return do_split; } static int split_large_page(pte_t *kpte, unsigned long address) { - unsigned long flags, pfn, pfninc = 1; + unsigned long pfn, pfninc = 1; unsigned int i, level; pte_t *pbase, *tmp; pgprot_t ref_prot; @@ -519,7 +519,8 @@ static int split_large_page(pte_t *kpte, if (!base) return -ENOMEM; - spin_lock_irqsave(&pgd_lock, flags); + VM_BUG_ON(in_interrupt()); + spin_lock(&pgd_lock); /* * Check for races, another CPU might have split this page * up for us already: @@ -591,7 +592,7 @@ out_unlock: */ if (base) __free_page(base); - spin_unlock_irqrestore(&pgd_lock, flags); + spin_unlock(&pgd_lock); return 0; } --- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -121,14 +121,13 @@ static void pgd_ctor(struct mm_struct *m static void pgd_dtor(pgd_t *pgd) { - unsigned long flags; /* can be called from interrupt context */ - if (SHARED_KERNEL_PMD) return; - spin_lock_irqsave(&pgd_lock, flags); + VM_BUG_ON(in_interrupt()); + spin_lock(&pgd_lock); pgd_list_del(pgd); - spin_unlock_irqrestore(&pgd_lock, flags); + spin_unlock(&pgd_lock); } /* @@ -260,7 +259,6 @@ pgd_t *pgd_alloc(struct mm_struct *mm) { pgd_t *pgd; pmd_t *pmds[PREALLOCATED_PMDS]; - unsigned long flags; pgd = (pgd_t *)__get_free_page(PGALLOC_GFP); @@ -280,12 +278,13 @@ pgd_t *pgd_alloc(struct mm_struct *mm) * respect to anything walking the pgd_list, so that they * never see a partially populated pgd. */ - spin_lock_irqsave(&pgd_lock, flags); + VM_BUG_ON(in_interrupt()); + spin_lock(&pgd_lock); pgd_ctor(mm, pgd); pgd_prepopulate_pmd(mm, pgd, pmds); - spin_unlock_irqrestore(&pgd_lock, flags); + spin_unlock(&pgd_lock); return pgd; --- a/arch/x86/xen/mmu.c +++ b/arch/x86/xen/mmu.c @@ -986,10 +986,9 @@ static void xen_pgd_pin(struct mm_struct */ void xen_mm_pin_all(void) { - unsigned long flags; struct page *page; - spin_lock_irqsave(&pgd_lock, flags); + spin_lock(&pgd_lock); list_for_each_entry(page, &pgd_list, lru) { if (!PagePinned(page)) { @@ -998,7 +997,7 @@ void xen_mm_pin_all(void) } } - spin_unlock_irqrestore(&pgd_lock, flags); + spin_unlock(&pgd_lock); } /* @@ -1099,10 +1098,9 @@ static void xen_pgd_unpin(struct mm_stru */ void xen_mm_unpin_all(void) { - unsigned long flags; struct page *page; - spin_lock_irqsave(&pgd_lock, flags); + spin_lock(&pgd_lock); list_for_each_entry(page, &pgd_list, lru) { if (PageSavePinned(page)) { @@ -1112,7 +1110,7 @@ void xen_mm_unpin_all(void) } } - spin_unlock_irqrestore(&pgd_lock, flags); + spin_unlock(&pgd_lock); } void xen_activate_mm(struct mm_struct *prev, struct mm_struct *next)