diff options
| author | Jiri Kosina | 2013-01-11 14:31:59 -0800 |
|---|---|---|
| committer | Linus Torvalds | 2013-01-11 14:54:55 -0800 |
| commit | 572043c90db65b45a4efd959db7458edcf6411ad (patch) | |
| tree | f14f009b4f900047cbf3f156232ecc2145bcb982 /mm | |
| parent | 1b963c81b14509e330e0fe3218b645ece2738dc5 (diff) | |
mm: mmap: annotate vm_lock_anon_vma locking properly for lockdep
Commit 5a505085f043 ("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
lock_acquire+0x121/0x190
down_write+0x3f/0x70
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
sys_ioctl+0x91/0xb0
system_call_fastpath+0x16/0x1b
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Cc: Rik van Riel <riel@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mel Gorman <mel@csn.ul.ie>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/mmap.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/mmap.c b/mm/mmap.c index f54b235f29a9..35730ee9d515 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 |