rcu/nocb: Reduce contention at no-CBs invocation-done time

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Currently, nocb_cb_wait() unconditionally acquires the leaf rcu_node
->lock to advance callbacks when done invoking the previous batch.
It does this while holding ->nocb_lock, which means that contention on
the leaf rcu_node ->lock visits itself on the ->nocb_lock.  This commit
therefore makes this lock acquisition conditional, forgoing callback
advancement when the leaf rcu_node ->lock is not immediately available.
(In this case, the no-CBs grace-period kthread will eventually do any
needed callback advancement.)

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

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This commit is contained in:

Paul E. McKenney 2019-06-01 13:33:55 -07:00

parent 6608c3a027

commit 523bddd553

1 changed files with 4 additions and 3 deletions

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kernel/rcu/tree_plugin.h

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