Messages in this thread Patch in this message | | | Date | Mon, 30 Apr 2012 12:04:20 +0100 | From | Catalin Marinas <> | Subject | Re: lockdep reports about recursive locking in kmemleak |
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On Fri, Apr 27, 2012 at 12:30:36PM +0100, Andrey Vagin wrote: > I found a following message in dmesg. Probably we should to do something > similar as for debug_objects, it sets own class for parent->list_lock. > Does anyone want to fix that? > > ============================================= > [ INFO: possible recursive locking detected ] > 3.3.0+ #87 Not tainted > --------------------------------------------- > udevd/847 is trying to acquire lock: > (&(&parent->list_lock)->rlock){-.-...}, at: [<ffffffff811783f1>] > cache_alloc_refill+0xa1/0x300 > > but task is already holding lock: > (&(&parent->list_lock)->rlock){-.-...}, at: [<ffffffff81177628>] > cache_flusharray+0x68/0x180 > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(&(&parent->list_lock)->rlock); > lock(&(&parent->list_lock)->rlock); > > *** DEADLOCK *** > > May be due to missing lock nesting notation > > 1 lock held by udevd/847: > #0: (&(&parent->list_lock)->rlock){-.-...}, at: [<ffffffff81177628>] > cache_flusharray+0x68/0x180
I'm not sure what the right fix is (cc'ing Christoph for the slab.c code). The lockdep warning is not in kmemleak, it just happens that cache_flusharray() (holding an l3->list_lock) triggers a new allocation via debug_object_activate() and kmemleak also tries to allocate its metadata, causing a cache_alloc_refill() call which acquires a different l3->list_lock, hence the lockdep warning.
Below is a quick fix but I don't know whether it could hide a real problem in the future:
diff --git a/mm/slab.c b/mm/slab.c index e901a36..3d2bfc6 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -3143,7 +3143,7 @@ retry: l3 = cachep->nodelists[node]; BUG_ON(ac->avail > 0 || !l3); - spin_lock(&l3->list_lock); + spin_lock_nested(&l3->list_lock, SINGLE_DEPTH_NESTING); /* See if we can refill from the shared array */ if (l3->shared && transfer_objects(ac, l3->shared, batchcount)) {
I'm leaving the original stack trace below for reference.
Catalin
> stack backtrace: > Pid: 847, comm: udevd Not tainted 3.3.0+ #87 > Call Trace: > [<ffffffff810b835a>] __lock_acquire+0x126a/0x1730 > [<ffffffff810b73f2>] ? __lock_acquire+0x302/0x1730 > [<ffffffff810b88d1>] lock_acquire+0xb1/0x1a0 > [<ffffffff811783f1>] ? cache_alloc_refill+0xa1/0x300 > [<ffffffff8118cdb9>] ? create_object+0x39/0x2e0 > [<ffffffff8153a141>] _raw_spin_lock+0x41/0x50 > [<ffffffff811783f1>] ? cache_alloc_refill+0xa1/0x300 > [<ffffffff811783f1>] cache_alloc_refill+0xa1/0x300 > [<ffffffff810b73f2>] ? __lock_acquire+0x302/0x1730 > [<ffffffff8118cdb9>] ? create_object+0x39/0x2e0 > [<ffffffff81179cbc>] kmem_cache_alloc+0x2cc/0x320 > [<ffffffff8118cdb9>] create_object+0x39/0x2e0 > [<ffffffff810b73f2>] ? __lock_acquire+0x302/0x1730 > [<ffffffff8151fade>] kmemleak_alloc+0x5e/0xc0 > [<ffffffff81179b2c>] kmem_cache_alloc+0x13c/0x320 > [<ffffffff81294d99>] __debug_object_init+0x3b9/0x3d0 > [<ffffffff812944fa>] ? debug_object_activate+0xca/0x190 > [<ffffffff81294dff>] debug_object_init+0x1f/0x30 > [<ffffffff810767d7>] rcuhead_fixup_activate+0x27/0x70 > [<ffffffff81293d35>] debug_object_fixup+0x15/0x20 > [<ffffffff8129450c>] debug_object_activate+0xdc/0x190 > [<ffffffff81177b50>] ? kmem_cache_shrink+0x70/0x70 > [<ffffffff810f0d12>] __call_rcu+0x42/0x1e0 > [<ffffffff810f0ee5>] call_rcu_sched+0x15/0x20 > [<ffffffff81177113>] slab_destroy+0x153/0x160 > [<ffffffff81177628>] ? cache_flusharray+0x68/0x180 > [<ffffffff81177179>] free_block+0x59/0x230 > [<ffffffff81177655>] cache_flusharray+0x95/0x180 > [<ffffffff81176dbf>] ? kmem_cache_free+0x11f/0x320 > [<ffffffff81176f6c>] kmem_cache_free+0x2cc/0x320 > [<ffffffff8115b5b1>] ? __put_anon_vma+0x61/0xb0 > [<ffffffff8115b5b1>] __put_anon_vma+0x61/0xb0 > [<ffffffff8115bb8b>] unlink_anon_vmas+0x13b/0x1a0 > [<ffffffff8114fac1>] free_pgtables+0x91/0x120 > [<ffffffff81156101>] exit_mmap+0xb1/0x120 > [<ffffffff8104e24b>] mmput+0x7b/0x120 > [<ffffffff81053d68>] exit_mm+0x108/0x130 > [<ffffffff8153aa70>] ? _raw_spin_unlock_irq+0x30/0x50 > [<ffffffff81056277>] do_exit+0x167/0x970 > [<ffffffff811b36c3>] ? mntput+0x23/0x40 > [<ffffffff81192f6d>] ? fput+0x1ad/0x280 > [<ffffffff8153ae59>] ? retint_swapgs+0x13/0x1b > [<ffffffff81056adb>] do_group_exit+0x5b/0xd0 > [<ffffffff81056b67>] sys_exit_group+0x17/0x20 > [<ffffffff81543729>] system_call_fastpath+0x16/0x1b
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