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    rcu: Suppress lockdep false positive for rcp->exp_funnel_mutex · 19a5ecde
    Paul E. McKenney 提交于
    In kernels built with CONFIG_PREEMPT=y, synchronize_rcu_expedited()
    invokes synchronize_sched_expedited() while holding RCU-preempt's
    root rcu_node structure's ->exp_funnel_mutex, which is acquired after
    the rcu_data structure's ->exp_funnel_mutex.  The first thing that
    synchronize_sched_expedited() will do is acquire RCU-sched's rcu_data
    structure's ->exp_funnel_mutex.   There is no danger of an actual deadlock
    because the locking order is always from RCU-preempt's expedited mutexes
    to those of RCU-sched.  Unfortunately, lockdep considers both rcu_data
    structures' ->exp_funnel_mutex to be in the same lock class and therefore
    reports a deadlock cycle.
    
    This commit silences this false positive by placing RCU-sched's rcu_data
    structures' ->exp_funnel_mutex locks into their own lock class.
    Reported-by: NSasha Levin <sasha.levin@oracle.com>
    Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
    19a5ecde
tree.c 133.0 KB