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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 <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2017-03-09 16:16:42 -08:00
parent f010ed82c7
commit c6e56f593a
1 changed files with 7 additions and 20 deletions
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27
kernel/rcu/srcu.c
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@ -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);