rcu: Silence lockdep false positive for expedited grace periods

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In a CONFIG_PREEMPT=y kernel, synchronize_rcu_expedited()
acquires the ->exp_funnel_mutex in rcu_preempt_state, then invokes
synchronize_sched_expedited, which acquires the ->exp_funnel_mutex in
rcu_sched_state.  There can be no deadlock because rcu_preempt_state
->exp_funnel_mutex acquisition always precedes that of rcu_sched_state.
But lockdep does not know that, so it gives false-positive splats.

This commit therefore associates a separate lock_class_key structure
with the rcu_sched_state structure's ->exp_funnel_mutex, allowing
lockdep to see the lock ordering, avoiding the false positives.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

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This commit is contained in:

Paul E. McKenney 2015-07-19 15:13:40 -07:00

parent cdacbe1f91

commit af859beaab

2 changed files with 18 additions and 2 deletions

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12

kernel/rcu/tree.c

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8

kernel/rcu/tree.h

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