linux-kernel - [PATCH rcu 16/18] rcu: Use per_cpu_ptr to get the pointer of per

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Date:   Wed, 21 Jul 2021 13:21:24 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com, mingo@...nel.org,
        jiangshanlai@...il.com, akpm@...ux-foundation.org,
        mathieu.desnoyers@...icios.com, josh@...htriplett.org,
        tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
        dhowells@...hat.com, edumazet@...gle.com, fweisbec@...il.com,
        oleg@...hat.com, joel@...lfernandes.org,
        Liu Song <liu.song11@....com.cn>,
        Uladzislau Rezki <urezki@...il.com>,
        Neeraj Upadhyay <neeraju@...eaurora.org>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH rcu 16/18] rcu: Use per_cpu_ptr to get the pointer of per_cpu variable

From: Liu Song <liu.song11@....com.cn>

There are a few remaining locations in kernel/rcu that still use
"&per_cpu()".  This commit replaces them with "per_cpu_ptr(&)", and does
not introduce any functional change.

Reviewed-by: Uladzislau Rezki (Sony) <urezki@...il.com>
Reviewed-by: Neeraj Upadhyay <neeraju@...eaurora.org>
Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>
Signed-off-by: Liu Song <liu.song11@....com.cn>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/tasks.h      | 2 +-
 kernel/rcu/tree.c       | 2 +-
 kernel/rcu/tree_stall.h | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 8536c55df5142..21f00194e69d7 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -920,7 +920,7 @@ static void trc_read_check_handler(void *t_in)
 	// Allow future IPIs to be sent on CPU and for task.
 	// Also order this IPI handler against any later manipulations of
 	// the intended task.
-	smp_store_release(&per_cpu(trc_ipi_to_cpu, smp_processor_id()), false); // ^^^
+	smp_store_release(per_cpu_ptr(&trc_ipi_to_cpu, smp_processor_id()), false); // ^^^
 	smp_store_release(&texp->trc_ipi_to_cpu, -1); // ^^^
 }
 
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 7b65ac3f49e5a..888efad0361d3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1292,7 +1292,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
 	 */
 	jtsq = READ_ONCE(jiffies_to_sched_qs);
 	ruqp = per_cpu_ptr(&rcu_data.rcu_urgent_qs, rdp->cpu);
-	rnhqp = &per_cpu(rcu_data.rcu_need_heavy_qs, rdp->cpu);
+	rnhqp = per_cpu_ptr(&rcu_data.rcu_need_heavy_qs, rdp->cpu);
 	if (!READ_ONCE(*rnhqp) &&
 	    (time_after(jiffies, rcu_state.gp_start + jtsq * 2) ||
 	     time_after(jiffies, rcu_state.jiffies_resched) ||
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index a8d0fcf0826f4..677ee3d8671bf 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -351,7 +351,7 @@ static void rcu_dump_cpu_stacks(void)
 
 static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
 {
-	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
+	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
 
 	sprintf(cp, "last_accelerate: %04lx/%04lx dyntick_enabled: %d",
 		rdp->last_accelerate & 0xffff, jiffies & 0xffff,
-- 
2.31.1.189.g2e36527f23