lkml.org 
[lkml]   [2011]   [Jun]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRe: slab vs lockdep vs debugobjects
    Date
    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@vger.kernel.org
    > 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 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/

    \
     
     \ /
      Last update: 2011-06-26 22:13    [W:0.032 / U:97.768 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site