From c6e56f593ac2df436700527c3488d4ed224c3acf Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 9 Mar 2017 16:16:42 -0800 Subject: [PATCH] srcu: Push srcu_advance_batches() fastpath into common case This commit simplifies the SRCU state machine by pushing the srcu_advance_batches() idle-SRCU fastpath into the common case. This is done by giving srcu_reschedule() a delay parameter, which is zero in the call from srcu_advance_batches(). This commit is a step towards numbering callbacks in order to efficiently handle per-CPU callback lists. Signed-off-by: Paul E. McKenney --- kernel/rcu/srcu.c | 27 +++++++-------------------- 1 file changed, 7 insertions(+), 20 deletions(-) diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c index 7e7ecaa50dc5..821ecda873f2 100644 --- a/kernel/rcu/srcu.c +++ b/kernel/rcu/srcu.c @@ -399,8 +399,7 @@ void call_srcu(struct srcu_struct *sp, struct rcu_head *head, } EXPORT_SYMBOL_GPL(call_srcu); -static void srcu_advance_batches(struct srcu_struct *sp, int trycount); -static void srcu_reschedule(struct srcu_struct *sp); +static void srcu_reschedule(struct srcu_struct *sp, unsigned long delay); /* * Helper function for synchronize_srcu() and synchronize_srcu_expedited(). @@ -409,7 +408,6 @@ static void __synchronize_srcu(struct srcu_struct *sp, int trycount) { struct rcu_synchronize rcu; struct rcu_head *head = &rcu.head; - bool done = false; RCU_LOCKDEP_WARN(lock_is_held(&sp->dep_map) || lock_is_held(&rcu_bh_lock_map) || @@ -431,25 +429,15 @@ static void __synchronize_srcu(struct srcu_struct *sp, int trycount) sp->running = true; rcu_batch_queue(&sp->batch_check0, head); spin_unlock_irq(&sp->queue_lock); - - srcu_advance_batches(sp, trycount); - if (!rcu_batch_empty(&sp->batch_done)) { - BUG_ON(sp->batch_done.head != head); - rcu_batch_dequeue(&sp->batch_done); - done = true; - } /* give the processing owner to work_struct */ - srcu_reschedule(sp); + srcu_reschedule(sp, 0); } else { rcu_batch_queue(&sp->batch_queue, head); spin_unlock_irq(&sp->queue_lock); } - if (!done) { - wait_for_completion(&rcu.completion); - smp_mb(); /* Caller's later accesses after GP. */ - } - + wait_for_completion(&rcu.completion); + smp_mb(); /* Caller's later accesses after GP. */ } /** @@ -639,7 +627,7 @@ static void srcu_invoke_callbacks(struct srcu_struct *sp) * Finished one round of SRCU grace period. Start another if there are * more SRCU callbacks queued, otherwise put SRCU into not-running state. */ -static void srcu_reschedule(struct srcu_struct *sp) +static void srcu_reschedule(struct srcu_struct *sp, unsigned long delay) { bool pending = true; @@ -653,8 +641,7 @@ static void srcu_reschedule(struct srcu_struct *sp) } if (pending) - queue_delayed_work(system_power_efficient_wq, - &sp->work, SRCU_INTERVAL); + queue_delayed_work(system_power_efficient_wq, &sp->work, delay); } /* @@ -669,6 +656,6 @@ void process_srcu(struct work_struct *work) srcu_collect_new(sp); srcu_advance_batches(sp, 1); srcu_invoke_callbacks(sp); - srcu_reschedule(sp); + srcu_reschedule(sp, SRCU_INTERVAL); } EXPORT_SYMBOL_GPL(process_srcu);