On Mon 17-06-13 19:14:12, Glauber Costa wrote: > On Mon, Jun 17, 2013 at 04:18:22PM +0200, Michal Hocko wrote: > > Hi, > > Hi, > > > 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. I am not sure I understand. Care to prepare a debugging patch for me? > Once we know each of them is misbehaving, then we'll have to figure > out why. > > Any special filesystem workload ? This is two parallel kernel builds with separate kernel trees running under 2 hard unlimitted groups (with 0 soft limit) followed by rm -rf source trees + drop caches. Sometimes I have to repeat this multiple times. I can also see some timer specific crashes which are most probably not related so I am getting back to my mm tree and will hope the tree is healthy. I have seen some other traces as well (mentioning ext3 dput paths) but I cannot reproduce them anymore. Thanks! -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>