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| author | Paul E. McKenney <paulmck@linux.ibm.com> | 2019-06-01 22:33:55 +0200 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.ibm.com> | 2019-08-13 23:35:49 +0200 |
| commit | 523bddd553c09a2cf051eb724bffba680424f5ec (patch) | |
| tree | 575f1bed80f45d6507d2c5533f4ede50c5b7ffb1 /kernel/rcu/tree_plugin.h | |
| parent | rcu/nocb: Reduce contention at no-CBs registry-time CB advancement (diff) | |
| download | linux-523bddd553c09a2cf051eb724bffba680424f5ec.tar.xz linux-523bddd553c09a2cf051eb724bffba680424f5ec.zip | |
rcu/nocb: Reduce contention at no-CBs invocation-done time
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>
Diffstat (limited to 'kernel/rcu/tree_plugin.h')
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 09c15f619e78..c4cbfb5dc48d 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1805,9 +1805,10 @@ static void nocb_cb_wait(struct rcu_data *rdp) local_bh_enable(); lockdep_assert_irqs_enabled(); rcu_nocb_lock_irqsave(rdp, flags); - raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ - needwake_gp = rcu_advance_cbs(rdp->mynode, rdp); - raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ + if (raw_spin_trylock_rcu_node(rnp)) { /* irqs already disabled. */ + needwake_gp = rcu_advance_cbs(rdp->mynode, rdp); + raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ + } if (rcu_segcblist_ready_cbs(&rdp->cblist)) { rcu_nocb_unlock_irqrestore(rdp, flags); if (needwake_gp) |