Markus Trippelsdorf [off-list ref] writes:

On 2011.12.18 at 19:21 -0800, Eric W. Biederman wrote:

quoted

Markus Trippelsdorf [off-list ref] writes:

quoted

On 2011.11.21 at 17:34 +0100, Markus Trippelsdorf wrote:

quoted

On 2011.11.21 at 17:10 +0100, Markus Trippelsdorf wrote:

quoted

On 2011.11.21 at 16:48 +0100, Eric Dumazet wrote:

quoted

Le lundi 21 novembre 2011 à 16:36 +0100, Markus Trippelsdorf a écrit :

quoted

On 2011.11.21 at 15:16 +0100, Eric Dumazet wrote:

quoted

Le lundi 21 novembre 2011 à 14:15 +0100, Markus Trippelsdorf a écrit :

quoted

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.

quoted

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.

Awesome.  

I guess that means I am only responsible for the Radeon driver having
the opportunity to take that code path. It is nice to see kexec being
used and being well known enough I didn't have to get involved.

Eric

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