tree 04082ce82de232a065436ed588edc56eb47018a0
parent 23a1b2a78705caa2ecaccf8422a1e22eaca59574
author Peter Zijlstra <a.p.zijlstra@chello.nl> 1165466173 -0800
committer Linus Torvalds <torvalds@woody.osdl.org> 1165509572 -0800

[PATCH] lockdep: fix ide/proc interaction

  rmmod/3080 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
   (proc_subdir_lock){--..}, at: [<c04a33b0>] remove_proc_entry+0x40/0x191

  and this task is already holding:
   (ide_lock){++..}, at: [<c05651a2>] ide_unregister_subdriver+0x39/0xc8
  which would create a new lock dependency:
   (ide_lock){++..} -> (proc_subdir_lock){--..}

  but this new dependency connects a hard-irq-safe lock:
   (ide_lock){++..}
  ... which became hard-irq-safe at:
    [<c043c458>] lock_acquire+0x4b/0x6b
    [<c06129d7>] _spin_lock_irqsave+0x22/0x32
    [<c0567870>] ide_intr+0x17/0x1a9
    [<c044eb31>] handle_IRQ_event+0x20/0x4d
    [<c044ebf2>] __do_IRQ+0x94/0xef
    [<c0406771>] do_IRQ+0x9e/0xbd

  to a hard-irq-unsafe lock:
   (proc_subdir_lock){--..}
  ... which became hard-irq-unsafe at:
  ...  [<c043c458>] lock_acquire+0x4b/0x6b
    [<c06126ab>] _spin_lock+0x19/0x28
    [<c04a32f2>] xlate_proc_name+0x1b/0x99
    [<c04a3547>] proc_create+0x46/0xdf
    [<c04a3642>] create_proc_entry+0x62/0xa5
    [<c07c1972>] proc_misc_init+0x1c/0x1d2
    [<c07c1844>] proc_root_init+0x4c/0xe9
    [<c07ad703>] start_kernel+0x294/0x3b3

Move ide_remove_proc_entries() out from under ide_lock; there is nothing
that indicates that this is needed.

In specific, the call to ide_add_proc_entries() is unprotected, and there
is nothing else in the file using the respective ->proc fields. Also the
lock order around destroy_proc_ide_interface() suggests this.

Alan sayeth:

  proc_ide_write_settings walks the setting list under ide_setting_sem, read
  ditto.  remove_proc_entry is doing proc side housekeeping.

  Looks fine to me, although that old code is such a mess anything could be
  going on.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>