futex: Fix errors in nested key ref-counting
authorDarren Hart <dvhart@linux.intel.com>
Sun, 17 Oct 2010 15:35:04 +0000 (08:35 -0700)
committerThomas Gleixner <tglx@linutronix.de>
Tue, 19 Oct 2010 09:41:54 +0000 (11:41 +0200)
commit7ada876a8703f23befbb20a7465a702ee39b1704
treeadee9cf8676fed56a0a6ad1d270ae5fb84d32553
parent2b666ca4a68cbc22483b0f2e1ba3c0e59b01ae9e
futex: Fix errors in nested key ref-counting

futex_wait() is leaking key references due to futex_wait_setup()
acquiring an additional reference via the queue_lock() routine. The
nested key ref-counting has been masking bugs and complicating code
analysis. queue_lock() is only called with a previously ref-counted
key, so remove the additional ref-counting from the queue_(un)lock()
functions.

Also futex_wait_requeue_pi() drops one key reference too many in
unqueue_me_pi(). Remove the key reference handling from
unqueue_me_pi(). This was paired with a queue_lock() in
futex_lock_pi(), so the count remains unchanged.

Document remaining nested key ref-counting sites.

Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Reported-and-tested-by: Matthieu Fertré<matthieu.fertre@kerlabs.com>
Reported-by: Louis Rilling<louis.rilling@kerlabs.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
LKML-Reference: <4CBB17A8.70401@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@kernel.org
kernel/futex.c