sched/rt: Fix lockdep annotation within find_lock_lowest_rq()
Roland Dreier reported spurious, hard to trigger lockdep warnings within the scheduler - without any real lockup. This bit gives us the right clue: > [89945.640512] [<ffffffff8103fa1a>] double_lock_balance+0x5a/0x90 > [89945.640568] [<ffffffff8104c546>] push_rt_task+0xc6/0x290 if you look at that code you'll find the double_lock_balance() in question is the one in find_lock_lowest_rq() [yay for inlining]. Now find_lock_lowest_rq() has a bug.. it fails to use double_unlock_balance() in one exit path, if this results in a retry in push_rt_task() we'll call double_lock_balance() again, at which point we'll run into said lockdep confusion. Reported-by:Roland Dreier <roland@kernel.org> Acked-by:
Steven Rostedt <rostedt@goodmis.org> Signed-off-by:
Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1337282386.4281.77.camel@twinsSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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