Re: linux-next: slab shrinkers: BUG at mm/list_lru.c:92
From: Andrew Morton
Date: Mon Jun 17 2013 - 17:35:19 EST
On Mon, 17 Jun 2013 19:14:12 +0400 Glauber Costa <glommer@xxxxxxxxx> wrote:
> > I managed to trigger:
> > [ 1015.776029] kernel BUG at mm/list_lru.c:92!
> > [ 1015.776029] invalid opcode: 0000 [#1] SMP
> > with Linux next (next-20130607) with https://lkml.org/lkml/2013/6/17/203
> > on top.
> > This is obviously BUG_ON(nlru->nr_items < 0) and
> > ffffffff81122d0b: 48 85 c0 test %rax,%rax
> > ffffffff81122d0e: 49 89 44 24 18 mov %rax,0x18(%r12)
> > ffffffff81122d13: 0f 84 87 00 00 00 je ffffffff81122da0 <list_lru_walk_node+0x110>
> > ffffffff81122d19: 49 83 7c 24 18 00 cmpq $0x0,0x18(%r12)
> > ffffffff81122d1f: 78 7b js ffffffff81122d9c <list_lru_walk_node+0x10c>
> > [...]
> > ffffffff81122d9c: 0f 0b ud2
> > RAX is -1UL.
> Yes, fearing those kind of imbalances, we decided to leave the counter as a signed quantity
> and BUG, instead of an unsigned quantity.
> > I assume that the current backtrace is of no use and it would most
> > probably be some shrinker which doesn't behave.
> There are currently 3 users of list_lru in tree: dentries, inodes and xfs.
> Assuming you are not using xfs, we are left with dentries and inodes.
> The first thing to do is to find which one of them is misbehaving. You can try finding
> this out by the address of the list_lru, and where it lays in the superblock.
> Once we know each of them is misbehaving, then we'll have to figure out why.
The trace says shrink_slab_node->super_cache_scan->prune_icache_sb. So
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