[RFC][PATCH v3 6/6] rcu/tree: Use irq_work_queue_remote()

[Peter Zijlstra <peterz@infradead.org>]

AFAICT we only need/use irq_work_queue_on() on remote CPUs, since we
can directly access local state.  So avoid the IRQ_WORK dependency and
use the unconditionally available irq_work_queue_remote().

This survives a number of TREE01 runs.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 kernel/rcu/tree.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1308,14 +1308,12 @@ static int rcu_implicit_dynticks_qs(stru
 			resched_cpu(rdp->cpu);
 			WRITE_ONCE(rdp->last_fqs_resched, jiffies);
 		}
-#ifdef CONFIG_IRQ_WORK
 		if (!rdp->rcu_iw_pending && rdp->rcu_iw_gp_seq != rnp->gp_seq &&
 		    (rnp->ffmask & rdp->grpmask)) {
 			rdp->rcu_iw_pending = true;
 			rdp->rcu_iw_gp_seq = rnp->gp_seq;
-			irq_work_queue_on(&rdp->rcu_iw, rdp->cpu);
+			irq_work_queue_remote(rdp->cpu, &rdp->rcu_iw);
 		}
-#endif
 	}
 
 	return 0;