From 64dfdf1e8291f162276df33c856b959124607078 Mon Sep 17 00:00:00 2001
From: "Paul E. McKenney" <paulmck@kernel.org>
Date: Tue, 9 Nov 2021 11:11:32 -0800
Subject: [PATCH] rcu-tasks: Add a ->percpu_enqueue_lim to the rcu_tasks
structure
References: bnc#1189998 (PREEMPT_RT prerequisite backports)
Patch-mainline: v5.17-rc0
Git-commit: 8dd593fddd630e7dcbe79e98ff5e0d0561e9ff27
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>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
kernel/rcu/tasks.h | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 0f672042151e..03c44c9b3909 100644
--- 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);