rcu: replace use of system_wq with system_percpu_wq

Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.

This lack of consistentcy cannot be addressed without refactoring the API.

system_wq is a per-CPU worqueue, yet nothing in its name tells about that
CPU affinity constraint, which is very often not required by users. Make
it clear by adding a system_percpu_wq.

The old wq will be kept for a few release cylces.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index f92443561d365a92e083e8890d11e14046765e1e..2dc044fd126eb0c0f25efd2da6fed43f759b79f8 100644 (file)
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -553,13 +553,13 @@ static void rcu_tasks_invoke_cbs(struct rcu_tasks *rtp, struct rcu_tasks_percpu
                rtpcp_next = rtp->rtpcp_array[index];
                if (rtpcp_next->cpu < smp_load_acquire(&rtp->percpu_dequeue_lim)) {
                        cpuwq = rcu_cpu_beenfullyonline(rtpcp_next->cpu) ? rtpcp_next->cpu : WORK_CPU_UNBOUND;
-                       queue_work_on(cpuwq, system_wq, &rtpcp_next->rtp_work);
+                       queue_work_on(cpuwq, system_percpu_wq, &rtpcp_next->rtp_work);
                        index++;
                        if (index < num_possible_cpus()) {
                                rtpcp_next = rtp->rtpcp_array[index];
                                if (rtpcp_next->cpu < smp_load_acquire(&rtp->percpu_dequeue_lim)) {
                                        cpuwq = rcu_cpu_beenfullyonline(rtpcp_next->cpu) ? rtpcp_next->cpu : WORK_CPU_UNBOUND;
-                                       queue_work_on(cpuwq, system_wq, &rtpcp_next->rtp_work);
+                                       queue_work_on(cpuwq, system_percpu_wq, &rtpcp_next->rtp_work);
                                }
                        }
                }