With debugobjects enabled and using SLAB_DESTROY_BY_RCU, when a
kmem_cache_node is destroyed the call_rcu() may trigger a slab
allocation to fill the debug object pool (__debug_object_init:fill_pool).
Everywhere but during kmem_cache_destroy(), discard_slab() is performed
outside of the kmem_cache_node->list_lock and avoids a lockdep warning
about potential recursion:
[ 138.850350] =============================================
[ 138.850352] [ INFO: possible recursive locking detected ]
[ 138.850355] 4.8.0-rc1-gfxbench+ #1 Tainted: G U
[ 138.850357] ---------------------------------------------
[ 138.850359] rmmod/8895 is trying to acquire lock:
[ 138.850360] (&(&n->list_lock)->rlock){-.-...}, at: [<ffffffff811c80d7>] get_partial_node.isra.63+0x47/0x430
[ 138.850368]
but task is already holding lock:
[ 138.850371] (&(&n->list_lock)->rlock){-.-...}, at: [<ffffffff811cbda4>] __kmem_cache_shutdown+0x54/0x320
[ 138.850376]
other info that might help us debug this:
[ 138.850378] Possible unsafe locking scenario:
[ 138.850380] CPU0
[ 138.850381] ----
[ 138.850382] lock(&(&n->list_lock)->rlock);
[ 138.850385] lock(&(&n->list_lock)->rlock);
[ 138.850387]
*** DEADLOCK ***
[ 138.850391] May be due to missing lock nesting notation
[ 138.850395] 5 locks held by rmmod/8895:
[ 138.850397] #0: (&dev->mutex){......}, at: [<ffffffff8156ce32>] driver_detach+0x42/0xc0
[ 138.850404] #1: (&dev->mutex){......}, at: [<ffffffff8156ce40>] driver_detach+0x50/0xc0
[ 138.850410] #2: (cpu_hotplug.dep_map){++++++}, at: [<ffffffff8107d65d>] get_online_cpus+0x2d/0x80
[ 138.850418] #3: (slab_mutex){+.+.+.}, at: [<ffffffff811964ec>] kmem_cache_destroy+0x3c/0x220
[ 138.850424] #4: (&(&n->list_lock)->rlock){-.-...}, at: [<ffffffff811cbda4>] __kmem_cache_shutdown+0x54/0x320
[ 138.850431]
stack backtrace:
[ 138.850435] CPU: 6 PID: 8895 Comm: rmmod Tainted: G U 4.8.0-rc1-gfxbench+ #1
[ 138.850439] Hardware name: Gigabyte Technology Co., Ltd. H87M-D3H/H87M-D3H, BIOS F11 08/18/2015
[ 138.850443] 0000000000000000 ffff880179b93800 ffffffff814221f5 ffff8801d1e5ce40
[ 138.850449] ffffffff827c6dd0 ffff880179b938c0 ffffffff810d48a6 00ffffff00000000
[ 138.850454] ffff88017990d900 ffff880179b93930 ffffffff0000d445 a70e0e46e14b0709
[ 138.850459] Call Trace:
[ 138.850463] [<ffffffff814221f5>] dump_stack+0x67/0x92
[ 138.850467] [<ffffffff810d48a6>] __lock_acquire+0x1646/0x1ad0
[ 138.850492] [<ffffffffa00e6a7b>] ? i915_exit+0x1a/0x1e2 [i915]
[ 138.850509] [<ffffffff810d5172>] lock_acquire+0xb2/0x200
[ 138.850512] [<ffffffff811c80d7>] ? get_partial_node.isra.63+0x47/0x430
[ 138.850516] [<ffffffff8180b8d6>] _raw_spin_lock+0x36/0x50
[ 138.850519] [<ffffffff811c80d7>] ? get_partial_node.isra.63+0x47/0x430
[ 138.850522] [<ffffffff811c80d7>] get_partial_node.isra.63+0x47/0x430
[ 138.850543] [<ffffffff8110e757>] ? __module_address+0x27/0xf0
[ 138.850558] [<ffffffffa00e6a7b>] ? i915_exit+0x1a/0x1e2 [i915]
[ 138.850561] [<ffffffff8110e82d>] ? __module_text_address+0xd/0x60
[ 138.850565] [<ffffffff811124ca>] ? is_module_text_address+0x2a/0x50
[ 138.850568] [<ffffffff8109ec51>] ? __kernel_text_address+0x31/0x80
[ 138.850572] [<ffffffff8101edd9>] ? print_context_stack+0x79/0xd0
[ 138.850575] [<ffffffff8101e584>] ? dump_trace+0x124/0x300
[ 138.850579] [<ffffffff811c9137>] ___slab_alloc.constprop.67+0x1a7/0x3b0
[ 138.850582] [<ffffffff8144109e>] ? __debug_object_init+0x2de/0x400
[ 138.850586] [<ffffffff810d0f07>] ? add_lock_to_list.isra.22.constprop.41+0x77/0xc0
[ 138.850590] [<ffffffff810d460e>] ? __lock_acquire+0x13ae/0x1ad0
[ 138.850594] [<ffffffff8144109e>] ? __debug_object_init+0x2de/0x400
[ 138.850597] [<ffffffff811c9383>] __slab_alloc.isra.64.constprop.66+0x43/0x80
[ 138.850601] [<ffffffff811c95f6>] kmem_cache_alloc+0x236/0x2d0
[ 138.850604] [<ffffffff8144109e>] ? __debug_object_init+0x2de/0x400
[ 138.850607] [<ffffffff8144109e>] __debug_object_init+0x2de/0x400
[ 138.850611] [<ffffffff81441309>] debug_object_activate+0x109/0x1e0
[ 138.850614] [<ffffffff811c8d60>] ? slab_cpuup_callback+0x100/0x100
[ 138.850618] [<ffffffff810ed242>] __call_rcu.constprop.63+0x32/0x2f0
[ 138.850621] [<ffffffff810ed512>] call_rcu+0x12/0x20
[ 138.850624] [<ffffffff811c7c8d>] discard_slab+0x3d/0x40
[ 138.850627] [<ffffffff811cbe2b>] __kmem_cache_shutdown+0xdb/0x320
[ 138.850631] [<ffffffff811964ec>] ? kmem_cache_destroy+0x3c/0x220
[ 138.850634] [<ffffffff81195a89>] shutdown_cache+0x19/0x60
[ 138.850638] [<ffffffff8119665e>] kmem_cache_destroy+0x1ae/0x220
[ 138.850650] [<ffffffffa0060e74>] i915_gem_load_cleanup+0x14/0x40 [i915]
[ 138.850660] [<ffffffffa001ffd1>] i915_driver_unload+0x151/0x180 [i915]
[ 138.850670] [<ffffffffa002a1c4>] i915_pci_remove+0x14/0x20 [i915]
[ 138.850673] [<ffffffff8146ef54>] pci_device_remove+0x34/0xb0
[ 138.850677] [<ffffffff8156cd05>] __device_release_driver+0x95/0x140
[ 138.850680] [<ffffffff8156cea6>] driver_detach+0xb6/0xc0
[ 138.850683] [<ffffffff8156bd53>] bus_remove_driver+0x53/0xd0
[ 138.850687] [<ffffffff8156d987>] driver_unregister+0x27/0x50
[ 138.850689] [<ffffffff8146dfb5>] pci_unregister_driver+0x25/0x70
[ 138.850704] [<ffffffffa00e6a7b>] i915_exit+0x1a/0x1e2 [i915]
[ 138.850707] [<ffffffff8110f3d3>] SyS_delete_module+0x193/0x1f0
[ 138.850711] [<ffffffff8180c429>] entry_SYSCALL_64_fastpath+0x1c/0xac
v2: Keep remove_partial() under the lock, just move discard_slab()
outside the lock.
Fixes: 52b4b950b507 ("mm: slab: free kmem_cache_node after destroy sysfs file")
Reported-by: Dave Gordon <david.s.gordon@xxxxxxxxx>
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Dmitry Safonov <dsafonov@xxxxxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Dave Gordon <david.s.gordon@xxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
---
mm/slub.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/mm/slub.c b/mm/slub.c
index 850737bdfbd8..08bb90d5f753 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3629,6 +3629,7 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page,
*/
static void free_partial(struct kmem_cache *s, struct kmem_cache_node *n)
{
+ LIST_HEAD(partial_list);
struct page *page, *h;
BUG_ON(irqs_disabled());
@@ -3636,13 +3637,16 @@ static void free_partial(struct kmem_cache *s, struct kmem_cache_node *n)
list_for_each_entry_safe(page, h, &n->partial, lru) {
if (!page->inuse) {
remove_partial(n, page);
- discard_slab(s, page);
+ list_add(&page->lru, &partial_list);
} else {
list_slab_objects(s, page,
"Objects remaining in %s on __kmem_cache_shutdown()");
}
}
spin_unlock_irq(&n->list_lock);
+
+ list_for_each_entry_safe(page, h, &partial_list, lru)
+ discard_slab(s, page);
}
/*
--
2.8.1
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