The sleep/wakeup of the no-CBs grace-period kthreads is synchronized using the ->nocb_lock of the first CPU corresponding to that kthread. This commit provides a separate ->nocb_gp_lock for this purpose, thus reducing contention on ->nocb_lock.
Signed-off-by: Paul E. McKenney <[email protected]> --- kernel/rcu/tree.h | 3 ++- kernel/rcu/tree_plugin.h | 9 +++++---- 2 files changed, 7 insertions(+), 5 deletions(-) diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 7062f9d9c053..2c3e9068671c 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -202,7 +202,8 @@ struct rcu_data { struct timer_list nocb_timer; /* Enforce finite deferral. */ /* The following fields are used by GP kthread, hence own cacheline. */ - bool nocb_gp_sleep ____cacheline_internodealigned_in_smp; + raw_spinlock_t nocb_gp_lock ____cacheline_internodealigned_in_smp; + bool nocb_gp_sleep; /* Is the nocb GP thread asleep? */ struct swait_queue_head nocb_gp_wq; /* For nocb kthreads to sleep on. */ bool nocb_cb_sleep; /* Is the nocb CB thread asleep? */ diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 7fbf2c4411a1..af9cbc7d4784 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1602,9 +1602,9 @@ static void wake_nocb_gp(struct rcu_data *rdp, bool force, del_timer(&rdp->nocb_timer); rcu_nocb_unlock_irqrestore(rdp, flags); smp_mb(); /* enqueue before ->nocb_gp_sleep. */ - rcu_nocb_lock_irqsave(rdp_gp, flags); + raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags); WRITE_ONCE(rdp_gp->nocb_gp_sleep, false); - rcu_nocb_unlock_irqrestore(rdp_gp, flags); + raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags); wake_up_process(rdp_gp->nocb_gp_kthread); } else { rcu_nocb_unlock_irqrestore(rdp, flags); @@ -1759,9 +1759,9 @@ static void nocb_gp_wait(struct rcu_data *my_rdp) trace_rcu_this_gp(rnp, my_rdp, wait_gp_seq, TPS("EndWait")); } if (!rcu_nocb_poll) { - rcu_nocb_lock_irqsave(my_rdp, flags); + raw_spin_lock_irqsave(&my_rdp->nocb_gp_lock, flags); WRITE_ONCE(my_rdp->nocb_gp_sleep, true); - rcu_nocb_unlock_irqrestore(my_rdp, flags); + raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags); } WARN_ON(signal_pending(current)); } @@ -1941,6 +1941,7 @@ static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) init_swait_queue_head(&rdp->nocb_cb_wq); init_swait_queue_head(&rdp->nocb_gp_wq); raw_spin_lock_init(&rdp->nocb_lock); + raw_spin_lock_init(&rdp->nocb_gp_lock); timer_setup(&rdp->nocb_timer, do_nocb_deferred_wakeup_timer, 0); } -- 2.17.1
