[PATCH 0/2 v6] lockdep: add support for queued rwlock

[Waiman Long <Waiman.Long@hp.com>]

v5->v6:
 - Unconditionally disallow the use of recursive read-lock in process
   context.
 - Promote read state 3 to 2 when in interrupt context instead of
   doing additional check in check_deadlock().
 - Fix some comments in locking-selftest.c.

v4->v5:
 - Add patch 2 to update the locking selftest code to handle recursive
   read_lock correctly. Patch 1 has no change.

v3->v4:
 - Document the new read state and move the conditional compilation code
   to lockdep.h.

v2->v3:
 - Add a new read mode (3) for rwlock (used in
   lock_acquire_shared_cond_recursive()) to avoid conflict with other
   use cases of lock_acquire_shared_recursive().

v1->v2:
 - Use less conditional & make it easier to read

With the merging of qrwlock into 3.16, it was found that the btrfs
filesystem hanged readily. A fix was devised and merged into rc2 and
the use of recursive read_lock call was part of the problem.

This patch series addes code to the lockdep subsystem to catch this
kind of recursive read_lock calls in kernel code. It also updates
the locking selftest to handle recursive read_lock correctly so that
it won't complain about test failures.

Waiman Long (2):
  locking/lockdep: Restrict the use of recursive read_lock() with
    qrwlock
  locking/selftest: Support queued rwlock

 include/linux/lockdep.h  |   10 +++++++++-
 kernel/locking/lockdep.c |    6 ++++++
 lib/locking-selftest.c   |   12 ++++++------
 3 files changed, 21 insertions(+), 7 deletions(-)