rcu-tasks: Add a ->percpu_enqueue_lim to the rcu_tasks structure

This commit adds a ->percpu_enqueue_lim field to the rcu_tasks structure.
This field contains two to the power of the ->percpu_enqueue_shift
field, easing construction of iterators over the per-CPU queues that
might contain RCU Tasks callbacks.  Such iterators will be introduced
in later commits.

Reported-by: Martin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index c11f4e646bf172c8013a39f6853a820ba8ed3a48..608af87a50658e40c8494e836bad90c62e0eead7 100644 (file)
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -52,6 +52,7 @@ struct rcu_tasks_percpu {
  * @call_func: This flavor's call_rcu()-equivalent function.
  * @rtpcpu: This flavor's rcu_tasks_percpu structure.
  * @percpu_enqueue_shift: Shift down CPU ID this much when enqueuing callbacks.
+ * @percpu_enqueue_lim: Number of per-CPU callback queues in use.
  * @name: This flavor's textual name.
  * @kname: This flavor's kthread name.
  */
@@ -76,6 +77,7 @@ struct rcu_tasks {
        call_rcu_func_t call_func;
        struct rcu_tasks_percpu __percpu *rtpcpu;
        int percpu_enqueue_shift;
+       int percpu_enqueue_lim;
        char *name;
        char *kname;
 };
@@ -93,6 +95,7 @@ static struct rcu_tasks rt_name =                                                     \
        .rtpcpu = &rt_name ## __percpu,                                                 \
        .name = n,                                                                      \
        .percpu_enqueue_shift = ilog2(CONFIG_NR_CPUS),                                  \
+       .percpu_enqueue_lim = 1,                                                        \
        .kname = #rt_name,                                                              \
 }
 
@@ -172,6 +175,7 @@ static void cblist_init_generic(struct rcu_tasks *rtp)
 
        raw_spin_lock_irqsave(&rtp->cbs_gbl_lock, flags);
        rtp->percpu_enqueue_shift = ilog2(nr_cpu_ids);
+       rtp->percpu_enqueue_lim = 1;
        for_each_possible_cpu(cpu) {
                struct rcu_tasks_percpu *rtpcp = per_cpu_ptr(rtp->rtpcpu, cpu);