I created a Bugzilla entry at https://bugzilla.kernel.org/show_bug.cgi?id=36912 for your bug report, please add your address to the CC list in there, thanks! On poniedziałek, 20 czerwca 2011 o 19:48:00 Peter Zijlstra wrote: > Hi Pekka, > > Thomas found a fun lockdep splat, see below. Basically call_rcu() can > end up in kmem_cache_alloc(), and call_rcu() is used under > l3->list_lock, causing the splat. Since the debug kmem_cache isn't > SLAB_DESTROY_BY_RCU this shouldn't ever actually recurse. > > Now, since this particular kmem_cache is created with > SLAB_DEBUG_OBJECTS, we thought it might be easy enough to set a separate > lockdep class for its l3->list_lock's. > > However I found that the existing lockdep annotation is for kmalloc only > -- don't custom kmem_caches use OFF_SLAB? > > Anyway, I got lost in slab (again), but would it make sense to move all > lockdep fixups into kmem_list3_init() or thereabouts? > > > --- > ============================================= > [ INFO: possible recursive locking detected ] > 3.0.0-rc3+ #37 > --------------------------------------------- > udevd/124 is trying to acquire lock: > (&(&parent->list_lock)->rlock){......}, at: [<ffffffff81119619>] > ____cache_alloc+0xc9/0x323 > > but task is already holding lock: > (&(&parent->list_lock)->rlock){......}, at: [<ffffffff8111844e>] > __cache_free+0x325/0x3ea > > 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 > > 2 locks held by udevd/124: > #0: (&(&(*({ do { const void *__vpp_verify = > (typeof((&(slab_lock))))((void *)0); (void)__vpp_verify; } while (0); ({ > unsigned long __ptr; __asm__ ("" : "=r"(__ptr) : > "0"((typeof(*(&(slab_lock))) *)(&(slab_lock)))); > (typeof((typeof(*(&(slab_lock))) *)(&(slab_lock)))) (__ptr + > (((__per_cpu_offset[__cpu])))); }); })).lock)->rlock){..-...}, at: > [<ffffffff811164cc>] __local_lock_irq+0x16/0x61 #1: > (&(&parent->list_lock)->rlock){......}, at: [<ffffffff8111844e>] > __cache_free+0x325/0x3ea > > stack backtrace: > Pid: 124, comm: udevd Not tainted 3.0.0-rc3+ #37 > Call Trace: > [<ffffffff81081e3d>] __lock_acquire+0x9ae/0xdc8 > [<ffffffff8107f289>] ? look_up_lock_class+0x5f/0xbe > [<ffffffff810812e4>] ? mark_lock+0x2d/0x1d8 > [<ffffffff81119619>] ? ____cache_alloc+0xc9/0x323 > [<ffffffff81082774>] lock_acquire+0x103/0x12e > [<ffffffff81119619>] ? ____cache_alloc+0xc9/0x323 > [<ffffffff8107f6b9>] ? register_lock_class+0x1e/0x2ca > [<ffffffff81247054>] ? __debug_object_init+0x43/0x2e7 > [<ffffffff814a7730>] _raw_spin_lock+0x3b/0x4a > [<ffffffff81119619>] ? ____cache_alloc+0xc9/0x323 > [<ffffffff81119619>] ____cache_alloc+0xc9/0x323 > [<ffffffff8107f6b9>] ? register_lock_class+0x1e/0x2ca > [<ffffffff81247054>] ? __debug_object_init+0x43/0x2e7 > [<ffffffff8111b0d5>] kmem_cache_alloc+0xc5/0x1fb > [<ffffffff81247054>] __debug_object_init+0x43/0x2e7 > [<ffffffff8124735f>] ? debug_object_activate+0x38/0xdc > [<ffffffff810812e4>] ? mark_lock+0x2d/0x1d8 > [<ffffffff8124730c>] debug_object_init+0x14/0x16 > [<ffffffff8106bd26>] rcuhead_fixup_activate+0x2b/0xbc > [<ffffffff81246d6f>] debug_object_fixup+0x1e/0x2b > [<ffffffff812473f6>] debug_object_activate+0xcf/0xdc > [<ffffffff81118b93>] ? kmem_cache_shrink+0x68/0x68 > [<ffffffff810b1fc0>] __call_rcu+0x4f/0x19e > [<ffffffff810b2124>] call_rcu+0x15/0x17 > [<ffffffff81117c4a>] slab_destroy+0x11f/0x157 > [<ffffffff81117dd4>] free_block+0x152/0x18d > [<ffffffff81118497>] __cache_free+0x36e/0x3ea > [<ffffffff81103b3b>] ? anon_vma_free+0x3d/0x41 > [<ffffffff811164cc>] ? __local_lock_irq+0x16/0x61 > [<ffffffff81117aad>] kmem_cache_free+0xa1/0x11f > [<ffffffff81103b3b>] anon_vma_free+0x3d/0x41 > [<ffffffff81104a77>] __put_anon_vma+0x38/0x3d > [<ffffffff81104aa5>] put_anon_vma+0x29/0x2d > [<ffffffff81104b7e>] unlink_anon_vmas+0x72/0xa5 > [<ffffffff810faa5b>] free_pgtables+0x6c/0xcb > [<ffffffff81100c96>] exit_mmap+0xc0/0xf7 > [<ffffffff8104de1d>] mmput+0x60/0xd3 > [<ffffffff81054112>] exit_mm+0x141/0x14e > [<ffffffff814a7d75>] ? _raw_spin_unlock_irq+0x54/0x61 > [<ffffffff8105436a>] do_exit+0x24b/0x74f > [<ffffffff811289ae>] ? fput+0x1d4/0x1e3 > [<ffffffff8107f539>] ? trace_hardirqs_off_caller+0x33/0x90 > [<ffffffff814a847d>] ? retint_swapgs+0x13/0x1b > [<ffffffff81054ae2>] do_group_exit+0x82/0xad > [<ffffffff81054b24>] sys_exit_group+0x17/0x1b > [<ffffffff814ae182>] system_call_fastpath+0x16/0x1b > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Maciej Rutecki http://www.maciek.unixy.pl -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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