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: [<ffffffff8115d549>] mm_take_all_locks+0x149/0x1b0
>
> but task is already holding lock:
> (&anon_vma->rwsem){+.+...}, at: [<ffffffff8115d549>] 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: [<ffffffff81177f1c>] do_mmu_notifier_register+0xfc/0x170
> #1: (mm_all_locks_mutex){+.+...}, at: [<ffffffff8115d436>] mm_take_all_locks+0x36/0x1b0
> #2: (&mapping->i_mmap_mutex){+.+...}, at: [<ffffffff8115d4c9>] mm_take_all_locks+0xc9/0x1b0
> #3: (&anon_vma->rwsem){+.+...}, at: [<ffffffff8115d549>] mm_take_all_locks+0x149/0x1b0
>
> stack backtrace:
> Pid: 2315, comm: qemu-kvm Not tainted 3.8.0-rc2-00036-g5f73896 #171
> Call Trace:
> [<ffffffff810afea2>] print_deadlock_bug+0xf2/0x100
> [<ffffffff810b1a76>] validate_chain+0x4f6/0x720
> [<ffffffff810b1ff9>] __lock_acquire+0x359/0x580
> [<ffffffff810b0e7d>] ? trace_hardirqs_on_caller+0x12d/0x1b0
> [<ffffffff810b2341>] lock_acquire+0x121/0x190
> [<ffffffff8115d549>] ? mm_take_all_locks+0x149/0x1b0
> [<ffffffff815a12bf>] down_write+0x3f/0x70
> [<ffffffff8115d549>] ? mm_take_all_locks+0x149/0x1b0
> [<ffffffff8115d549>] mm_take_all_locks+0x149/0x1b0
> [<ffffffff81177e88>] do_mmu_notifier_register+0x68/0x170
> [<ffffffff81177fae>] mmu_notifier_register+0xe/0x10
> [<ffffffffa04bd6ab>] kvm_create_vm+0x22b/0x330 [kvm]
> [<ffffffffa04bd8a8>] kvm_dev_ioctl+0xf8/0x1a0 [kvm]
> [<ffffffff811a45bd>] do_vfs_ioctl+0x9d/0x350
> [<ffffffff815ad215>] ? sysret_check+0x22/0x5d
> [<ffffffff811a4901>] sys_ioctl+0x91/0xb0
> [<ffffffff815ad1e9>] system_call_fastpath+0x16/0x1b
>
> Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
> ---
> 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
> --
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--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
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