Re: WARNING: at mm/slub.c:3357, kernel BUG at mm/slub.c:3413

[Markus Trippelsdorf]

On 2011.12.18 at 19:21 -0800, Eric W. Biederman wrote:
> Markus Trippelsdorf <markus@xxxxxxxxxxxxxxx> writes:
> 
> > On 2011.11.21 at 17:34 +0100, Markus Trippelsdorf wrote:
> >> On 2011.11.21 at 17:10 +0100, Markus Trippelsdorf wrote:
> >> > On 2011.11.21 at 16:48 +0100, Eric Dumazet wrote:
> >> > > Le lundi 21 novembre 2011 à 16:36 +0100, Markus Trippelsdorf a écrit :
> >> > > > On 2011.11.21 at 15:16 +0100, Eric Dumazet wrote:
> >> > > > > Le lundi 21 novembre 2011 à 14:15 +0100, Markus Trippelsdorf a écrit :
> >> > > > > 
> >> > > > > > I've enabled CONFIG_SLUB_DEBUG_ON and this is what happend:
> >> > > > > > 
> >> > > > > 
> >> > > > > Thanks
> >> > > > > 
> >> > > > > Please continue to provide more samples.
> >> > > > > 
> >> > > > > There is something wrong somewhere, but where exactly, its hard to say.
> >> > > > 
> >> > > > New sample. This one points to lib/idr.c:
> >> > > > 
> >> > > > =============================================================================
> >> > > > BUG idr_layer_cache: Poison overwritten
> >> > > > -----------------------------------------------------------------------------
> >> > > 
> >> > > Thanks, could you now add "CONFIG_DEBUG_PAGEALLOC=y" in your config as
> >> > > well ?
> >> > 
> >> > Sure. This one happend with CONFIG_DEBUG_PAGEALLOC=y:
> >> > 
> >> > =============================================================================
> >> > BUG task_struct: Poison overwritten
> >> > -----------------------------------------------------------------------------
> >> 
> >> And sometimes this one that I've reported earlier already:
> >> 
> >> (see: http://thread.gmane.org/gmane.linux.kernel/1215023 )
> >> 
> >>  ------------[ cut here ]------------
> >>  WARNING: at fs/sysfs/sysfs.h:195 sysfs_get_inode+0x136/0x140()
> >>  Hardware name: System Product Name
> >>  Pid: 1876, comm: slabinfo Not tainted 3.2.0-rc2-00274-g6fe4c6d #72
> >>  Call Trace:
> >>  [<ffffffff8106cac5>] warn_slowpath_common+0x75/0xb0
> >>  [<ffffffff8106cbc5>] warn_slowpath_null+0x15/0x20
> >>  [<ffffffff81163236>] sysfs_get_inode+0x136/0x140
> >>  [<ffffffff81164cef>] sysfs_lookup+0x6f/0x110
> >>  [<ffffffff811173f9>] d_alloc_and_lookup+0x39/0x80
> >>  [<ffffffff81118774>] do_lookup+0x294/0x3a0
> >>  [<ffffffff8111798a>] ? inode_permission+0x7a/0xb0
> >>  [<ffffffff8111a3f7>] do_last.isra.46+0x137/0x7f0
> >>  [<ffffffff8111ab76>] path_openat+0xc6/0x370
> >>  [<ffffffff81117606>] ? getname_flags+0x36/0x230
> >>  [<ffffffff810ec852>] ? handle_mm_fault+0x192/0x290
> >>  [<ffffffff8111ae5c>] do_filp_open+0x3c/0x90
> >>  [<ffffffff81127c8c>] ? alloc_fd+0xdc/0x120
> >>  [<ffffffff8110ce77>] do_sys_open+0xe7/0x1c0
> >>  [<ffffffff8110cf6b>] sys_open+0x1b/0x20
> >>  [<ffffffff814ccb7b>] system_call_fastpath+0x16/0x1b
> >>  ---[ end trace b1377eb8b131d37d ]---
> >
> > Hm, the "sysfs: use rb-tree" thing hit again during boot. Could this be
> > the root cause of this all?
> >
> > I wrote down the following:
> >
> > RIP : rb_next
> >
> > Trace:
> >  sysfs_dir_pos
> >  sysfs_readdir
> >  ? sys_ioctl
> >  vfs_readdir
> >  sys_getdents
> 
> Thanks for reporting this.
> 
> Has this by any chance been resolved or stopped happening?

Yes.

> This looks for all of the world like something is stomping your sysfs
> dirents.   I haven't seen anyone else complaining so this seems like the
> problem is unique to your configuration.  Which suggests that it is not
> sysfs itself that is wrong.
> 
> I have been through the code a time or two and I haven't seen anything
> obviously wrong.  Everything that sysfs does is protected by the
> sysfs_mutex so the locking is very very simple.
> 
> My best guess of why now is that the rbtree code make a sysfs dirent
> 48 bytes larger.  And so it is much more exposed to these kinds of
> problems.

Sorry, but your subsystem was just accidentally hit by a bug in the
Radeon driver, that sometimes randomly writes 0 dwords somewhere to
memory after a kexec boot (see the rest of this huge thread).
It's still not fixed in mainline, because Linus refused to take the fix
this late in the series.

-- 
Markus
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