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Date: Tue, 18 Jun 2013 12:44:43 +0200 From: Michal Hocko <mhocko@...e.cz> To: Glauber Costa <glommer@...il.com> Cc: Dave Chinner <david@...morbit.com>, Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org> Subject: Re: linux-next: slab shrinkers: BUG at mm/list_lru.c:92 On Tue 18-06-13 10:24:14, Michal Hocko wrote: > On Tue 18-06-13 10:31:05, Glauber Costa wrote: > > On Tue, Jun 18, 2013 at 12:46:23PM +1000, Dave Chinner wrote: > > > On Tue, Jun 18, 2013 at 02:30:05AM +0400, Glauber Costa wrote: > > > > On Mon, Jun 17, 2013 at 02:35:08PM -0700, Andrew Morton wrote: > > > > > On Mon, 17 Jun 2013 19:14:12 +0400 Glauber Costa <glommer@...il.com> 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 > > > > > it's inodes? > > > > > > > > > Assuming there is no memory corruption of any sort going on , let's check the code. > > > > nr_item is only manipulated in 3 places: > > > > > > > > 1) list_lru_add, where it is increased > > > > 2) list_lru_del, where it is decreased in case the user have voluntarily removed the > > > > element from the list > > > > 3) list_lru_walk_node, where an element is removing during shrink. > > > > > > > > All three excerpts seem to be correctly locked, so something like this indicates an imbalance. > > > > > > inode_lru_isolate() looks suspicious to me: > > > > > > WARN_ON(inode->i_state & I_NEW); > > > inode->i_state |= I_FREEING; > > > spin_unlock(&inode->i_lock); > > > > > > list_move(&inode->i_lru, freeable); > > > this_cpu_dec(nr_unused); > > > return LRU_REMOVED; > > > } > > > > > > All the other cases where I_FREEING is set and the inode is removed > > > from the LRU are completely done under the inode->i_lock. i.e. from > > > an external POV, the state change to I_FREEING and removal from LRU > > > are supposed to be atomic, but they are not here. > > > > > > I'm not sure this is the source of the problem, but it definitely > > > needs fixing. > > > > > Yes, I missed that yesterday, but that does look suspicious to me as well. > > > > Michal, if you can manually move this one inside the lock as well and see > > if it fixes your problem as well... Otherwise I can send you a patch as well > > so we don't get lost on what is patched and what is not. > > OK, I am testing with this now: > diff --git a/fs/inode.c b/fs/inode.c > index 604c15e..95e598c 100644 > --- a/fs/inode.c > +++ b/fs/inode.c > @@ -733,9 +733,9 @@ inode_lru_isolate(struct list_head *item, spinlock_t *lru_lock, void *arg) > > WARN_ON(inode->i_state & I_NEW); > inode->i_state |= I_FREEING; > + list_move(&inode->i_lru, freeable); > spin_unlock(&inode->i_lock); > > - list_move(&inode->i_lru, freeable); > this_cpu_dec(nr_unused); > return LRU_REMOVED; > } And this hung again: 4434 pts/0 S+ 0:00 /bin/sh ./run_batch.sh mmotmdebug 4436 pts/0 S+ 0:00 /bin/bash ./start.sh 4441 pts/0 S+ 0:26 /bin/bash ./start.sh 1919 pts/0 S+ 0:00 sleep 1s 4457 pts/0 S+ 0:00 /bin/bash ./run_test.sh /dev/cgroup A 2 4459 pts/0 S+ 0:27 /bin/bash ./run_test.sh /dev/cgroup A 2 1913 pts/0 S+ 0:00 sleep 1s 5626 pts/0 S+ 0:00 /usr/bin/time -v make -j4 vmlinux 5628 pts/0 S+ 0:00 make -j4 vmlinux 2676 pts/0 S+ 0:00 make -f scripts/Makefile.build obj=sound 2893 pts/0 S+ 0:00 make -f scripts/Makefile.build obj=sound/pci 2998 pts/0 D+ 0:00 make -f scripts/Makefile.build obj=sound/pci/emu10k1 6590 pts/0 D+ 0:00 make -f scripts/Makefile.build obj=net 4458 pts/0 S+ 0:00 /bin/bash ./run_test.sh /dev/cgroup B 2 4464 pts/0 S+ 0:27 /bin/bash ./run_test.sh /dev/cgroup B 2 1914 pts/0 S+ 0:00 sleep 1s 5625 pts/0 S+ 0:00 /usr/bin/time -v make -j4 vmlinux 5627 pts/0 S+ 0:00 make -j4 vmlinux 13010 pts/0 D+ 0:00 make -f scripts/Makefile.build obj=kernel 3933 pts/0 Z+ 0:00 [sh] <defunct> 14459 pts/0 S+ 0:00 make -f scripts/Makefile.build obj=fs 784 pts/0 D+ 0:00 make -f scripts/Makefile.build obj=fs/romfs 2401 pts/0 S+ 0:00 make -f scripts/Makefile.build obj=crypto 4614 pts/0 D+ 0:00 make -f scripts/Makefile.build obj=crypto/asymmetric_keys 3343 pts/0 S+ 0:00 make -f scripts/Makefile.build obj=block 5167 pts/0 D+ 0:00 make -f scripts/Makefile.build obj=block/partitions demon:/home/mhocko # cat /proc/2998/stack [<ffffffff8118325e>] __wait_on_freeing_inode+0x9e/0xc0 [<ffffffff81183321>] find_inode_fast+0xa1/0xc0 [<ffffffff8118525f>] iget_locked+0x4f/0x180 [<ffffffff811ef9e3>] ext4_iget+0x33/0x9f0 [<ffffffff811f6a1c>] ext4_lookup+0xbc/0x160 [<ffffffff81174ad0>] lookup_real+0x20/0x60 [<ffffffff81177e25>] lookup_open+0x175/0x1d0 [<ffffffff8117815e>] do_last+0x2de/0x780 [<ffffffff8117ae9a>] path_openat+0xda/0x400 [<ffffffff8117b303>] do_filp_open+0x43/0xa0 [<ffffffff81168ee0>] do_sys_open+0x160/0x1e0 [<ffffffff81168f9c>] sys_open+0x1c/0x20 [<ffffffff81582fe9>] system_call_fastpath+0x16/0x1b [<ffffffffffffffff>] 0xffffffffffffffff demon:/home/mhocko # cat /proc/6590/stack [<ffffffff8118325e>] __wait_on_freeing_inode+0x9e/0xc0 [<ffffffff81183321>] find_inode_fast+0xa1/0xc0 [<ffffffff8118525f>] iget_locked+0x4f/0x180 [<ffffffff811ef9e3>] ext4_iget+0x33/0x9f0 [<ffffffff811f6a1c>] ext4_lookup+0xbc/0x160 [<ffffffff81174ad0>] lookup_real+0x20/0x60 [<ffffffff81175254>] __lookup_hash+0x34/0x40 [<ffffffff81179872>] path_lookupat+0x7a2/0x830 [<ffffffff81179933>] filename_lookup+0x33/0xd0 [<ffffffff8117ab0b>] user_path_at_empty+0x7b/0xb0 [<ffffffff8117ab4c>] user_path_at+0xc/0x10 [<ffffffff8116ff91>] vfs_fstatat+0x51/0xb0 [<ffffffff81170116>] vfs_stat+0x16/0x20 [<ffffffff8117013f>] sys_newstat+0x1f/0x50 [<ffffffff81582fe9>] system_call_fastpath+0x16/0x1b [<ffffffffffffffff>] 0xffffffffffffffff demon:/home/mhocko # cat /proc/13010/stack [<ffffffff8118325e>] __wait_on_freeing_inode+0x9e/0xc0 [<ffffffff81183321>] find_inode_fast+0xa1/0xc0 [<ffffffff8118525f>] iget_locked+0x4f/0x180 [<ffffffff811ef9e3>] ext4_iget+0x33/0x9f0 [<ffffffff811f6a1c>] ext4_lookup+0xbc/0x160 [<ffffffff81174ad0>] lookup_real+0x20/0x60 [<ffffffff81175254>] __lookup_hash+0x34/0x40 [<ffffffff81179872>] path_lookupat+0x7a2/0x830 [<ffffffff81179933>] filename_lookup+0x33/0xd0 [<ffffffff8117ab0b>] user_path_at_empty+0x7b/0xb0 [<ffffffff8117ab4c>] user_path_at+0xc/0x10 [<ffffffff8116ff91>] vfs_fstatat+0x51/0xb0 [<ffffffff81170116>] vfs_stat+0x16/0x20 [<ffffffff8117013f>] sys_newstat+0x1f/0x50 [<ffffffff81582fe9>] system_call_fastpath+0x16/0x1b [<ffffffffffffffff>] 0xffffffffffffffff demon:/home/mhocko # cat /proc/784/stack [<ffffffff8118325e>] __wait_on_freeing_inode+0x9e/0xc0 [<ffffffff81183321>] find_inode_fast+0xa1/0xc0 [<ffffffff8118525f>] iget_locked+0x4f/0x180 [<ffffffff811ef9e3>] ext4_iget+0x33/0x9f0 [<ffffffff811f6a1c>] ext4_lookup+0xbc/0x160 [<ffffffff81174ad0>] lookup_real+0x20/0x60 [<ffffffff81175254>] __lookup_hash+0x34/0x40 [<ffffffff81179872>] path_lookupat+0x7a2/0x830 [<ffffffff81179933>] filename_lookup+0x33/0xd0 [<ffffffff8117ab0b>] user_path_at_empty+0x7b/0xb0 [<ffffffff8117ab4c>] user_path_at+0xc/0x10 [<ffffffff8116ff91>] vfs_fstatat+0x51/0xb0 [<ffffffff81170116>] vfs_stat+0x16/0x20 [<ffffffff8117013f>] sys_newstat+0x1f/0x50 [<ffffffff81582fe9>] system_call_fastpath+0x16/0x1b [<ffffffffffffffff>] 0xffffffffffffffff demon:/home/mhocko # cat /proc/4614/stack [<ffffffff8117d0ca>] vfs_readdir+0x7a/0xc0 [<ffffffff8117d1a6>] sys_getdents64+0x96/0x100 [<ffffffff81582fe9>] system_call_fastpath+0x16/0x1b [<ffffffffffffffff>] 0xffffffffffffffff demon:/home/mhocko # cat /proc/5167/stack [<ffffffff8117d0ca>] vfs_readdir+0x7a/0xc0 [<ffffffff8117d1a6>] sys_getdents64+0x96/0x100 [<ffffffff81582fe9>] system_call_fastpath+0x16/0x1b [<ffffffffffffffff>] 0xffffffffffffffff JFYI: This is still with my -mm git tree + the above diff + referenced patch from Mel (mm: Clear page active before releasing pages). -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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