From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx116.postini.com [74.125.245.116]) by kanga.kvack.org (Postfix) with SMTP id 0AA5C6B006C for ; Fri, 11 Jan 2013 12:00:41 -0500 (EST) Date: Fri, 11 Jan 2013 18:00:38 +0100 From: Borislav Petkov Subject: Re: [PATCH 2/2] mm: mmap: annotate vm_lock_anon_vma locking properly for lockdep Message-ID: <20130111170038.GC21882@liondog.tnic> References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Jiri Kosina Cc: Rik van Riel , Ingo Molnar , Peter Zijlstra , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org Ok, I see this still on -rc3, also with kvm. Will run your patches and verify them. Thanks. On Sat, Jan 05, 2013 at 01:35:45AM +0100, Jiri Kosina wrote: > Commit 5a505085f04 ("mm/rmap: Convert the struct anon_vma::mutex to an > rwsem") turned anon_vma mutex to rwsem. > > However, the properly annotated nested locking in mm_take_all_locks() has > been converted from > > mutex_lock_nest_lock(&anon_vma->root->mutex, &mm->mmap_sem); > > to > > down_write(&anon_vma->root->rwsem); > > which is incomplete, and causes the false positive report from lockdep below. > > Annotate the fact that mmap_sem is used as an outter lock to serialize taking > of all the anon_vma rwsems at once no matter the order, using the > down_write_nest_lock() primitive. > > This patch fixes this lockdep report: > > ============================================= > [ INFO: possible recursive locking detected ] > 3.8.0-rc2-00036-g5f73896 #171 Not tainted > --------------------------------------------- > qemu-kvm/2315 is trying to acquire lock: > (&anon_vma->rwsem){+.+...}, at: [] mm_take_all_locks+0x149/0x1b0 > > but task is already holding lock: > (&anon_vma->rwsem){+.+...}, at: [] mm_take_all_locks+0x149/0x1b0 > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(&anon_vma->rwsem); > lock(&anon_vma->rwsem); > > *** DEADLOCK *** > > May be due to missing lock nesting notation > > 4 locks held by qemu-kvm/2315: > #0: (&mm->mmap_sem){++++++}, at: [] do_mmu_notifier_register+0xfc/0x170 > #1: (mm_all_locks_mutex){+.+...}, at: [] mm_take_all_locks+0x36/0x1b0 > #2: (&mapping->i_mmap_mutex){+.+...}, at: [] mm_take_all_locks+0xc9/0x1b0 > #3: (&anon_vma->rwsem){+.+...}, at: [] mm_take_all_locks+0x149/0x1b0 > > stack backtrace: > Pid: 2315, comm: qemu-kvm Not tainted 3.8.0-rc2-00036-g5f73896 #171 > Call Trace: > [] print_deadlock_bug+0xf2/0x100 > [] validate_chain+0x4f6/0x720 > [] __lock_acquire+0x359/0x580 > [] ? trace_hardirqs_on_caller+0x12d/0x1b0 > [] lock_acquire+0x121/0x190 > [] ? mm_take_all_locks+0x149/0x1b0 > [] down_write+0x3f/0x70 > [] ? mm_take_all_locks+0x149/0x1b0 > [] mm_take_all_locks+0x149/0x1b0 > [] do_mmu_notifier_register+0x68/0x170 > [] mmu_notifier_register+0xe/0x10 > [] kvm_create_vm+0x22b/0x330 [kvm] > [] kvm_dev_ioctl+0xf8/0x1a0 [kvm] > [] do_vfs_ioctl+0x9d/0x350 > [] ? sysret_check+0x22/0x5d > [] sys_ioctl+0x91/0xb0 > [] system_call_fastpath+0x16/0x1b > > Signed-off-by: Jiri Kosina > --- > mm/mmap.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index f54b235..35730ee 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -2886,7 +2886,7 @@ static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma) > * The LSB of head.next can't change from under us > * because we hold the mm_all_locks_mutex. > */ > - down_write(&anon_vma->root->rwsem); > + down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_sem); > /* > * We can safely modify head.next after taking the > * anon_vma->root->rwsem. If some other vma in this mm shares > -- > Jiri Kosina > SUSE Labs > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- Regards/Gruss, Boris. Sent from a fat crate under my desk. Formatting is fine. -- -- 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