Re: [PATCH driver-core-linus] kernfs: make kernfs_deactivate() honor KERNFS_LOCKDEP flag

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Wed, Jan 29, 2014 at 03:19:51PM -0200, Fabio Estevam wrote:
> On Wed, Jan 29, 2014 at 3:04 PM, Tejun Heo <tj@kernel.org> wrote:
> > kernfs_deactivate() forgot to check whether KERNFS_LOCKDEP is set
> > before performing lockdep annotations and ends up feeding
> > uninitialized lockdep_map to lockdep triggering warning like the
> > following on USB stick hotunplug.
> >
> >  usb 1-2: USB disconnect, device number 2
> >  INFO: trying to register non-static key.
> >  the code is fine but needs lockdep annotation.
> >  turning off the locking correctness validator.
> >  CPU: 1 PID: 62 Comm: khubd Not tainted 3.13.0-work+ #82
> >  Hardware name: empty empty/S3992, BIOS 080011  10/26/2007
> >   ffff880065ca7f60 ffff88013a4ffa08 ffffffff81cfb6bd 0000000000000002
> >   ffff88013a4ffac8 ffffffff810f8530 ffff88013a4fc710 0000000000000002
> >   ffff880100000000 ffffffff82a3db50 0000000000000001 ffff88013a4fc710
> >  Call Trace:
> >   [<ffffffff81cfb6bd>] dump_stack+0x4e/0x7a
> >   [<ffffffff810f8530>] __lock_acquire+0x1910/0x1e70
> >   [<ffffffff810f931a>] lock_acquire+0x9a/0x1d0
> >   [<ffffffff8127c75e>] kernfs_deactivate+0xee/0x130
> >   [<ffffffff8127d4c8>] kernfs_addrm_finish+0x38/0x60
> >   [<ffffffff8127d701>] kernfs_remove_by_name_ns+0x51/0xa0
> >   [<ffffffff8127b4f1>] remove_files.isra.1+0x41/0x80
> >   [<ffffffff8127b7e7>] sysfs_remove_group+0x47/0xa0
> >   [<ffffffff8127b873>] sysfs_remove_groups+0x33/0x50
> >   [<ffffffff8177d66d>] device_remove_attrs+0x4d/0x80
> >   [<ffffffff8177e25e>] device_del+0x12e/0x1d0
> >   [<ffffffff819722c2>] usb_disconnect+0x122/0x1a0
> >   [<ffffffff819749b5>] hub_thread+0x3c5/0x1290
> >   [<ffffffff810c6a6d>] kthread+0xed/0x110
> >   [<ffffffff81d0a56c>] ret_from_fork+0x7c/0xb0
> >
> > Fix it by making kernfs_deactivate() perform lockdep annotations only
> > if KERNFS_LOCKDEP is set.
> >
> > Signed-off-by: Tejun Heo <tj@kernel.org>
> > Reported-by: Fabio Estevam <festevam@gmail.com>
> > Reported-by: Alan Stern <stern@rowland.harvard.edu>
> 
> Thanks, Tejun. I don't get the warning after removing the USB stick
> after applying this patch:
> 
> Tested-by: Fabio Estevam <fabio.estevam@freescale.com>

Great, I'll queue this up and get it to Linus after 3.14-rc1 is out.

thanks,

greg k-h