linux-kernel - [PATCH v2 1/3] sched/topology: Annotate RCU pointers properly

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Date: Mon, 15 Jan 2024 15:34:24 +0100
From: Pierre Gondois <pierre.gondois@....com>
To: linux-kernel@...r.kernel.org
Cc: Shrikanth Hegde <sshegde@...ux.vnet.ibm.com>,
	Pierre Gondois <pierre.gondois@....com>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>,
	Mel Gorman <mgorman@...e.de>,
	Daniel Bristot de Oliveira <bristot@...hat.com>,
	Valentin Schneider <vschneid@...hat.com>,
	Huang Ying <ying.huang@...el.com>
Subject: [PATCH v2 1/3] sched/topology: Annotate RCU pointers properly

Cleanup RCU-related spare errors by annotating RCU pointers.

sched_domains_numa_distance:
  error: incompatible types in comparison expression
  (different address spaces):
      int [noderef] __rcu *
      int *

sched_domains_numa_masks:
  error: incompatible types in comparison expression
  (different address spaces):
      struct cpumask **[noderef] __rcu *
      struct cpumask ***

The cast to (void *) adds the following sparse warning:
  warning: cast removes address space '__rcu' of expression
but this should be normal.

Fixes: 0fb3978b0aac ("sched/numa: Fix NUMA topology for systems with CPU-less nodes")
Signed-off-by: Pierre Gondois <pierre.gondois@....com>
---
 kernel/sched/topology.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 10d1391e7416..2a2da9b33e31 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -1542,8 +1542,8 @@ static int			sched_domains_numa_levels;
 static int			sched_domains_curr_level;
 
 int				sched_max_numa_distance;
-static int			*sched_domains_numa_distance;
-static struct cpumask		***sched_domains_numa_masks;
+static int			__rcu *sched_domains_numa_distance;
+static struct cpumask		** __rcu *sched_domains_numa_masks;
 #endif
 
 /*
@@ -1988,8 +1988,8 @@ void sched_init_numa(int offline_node)
 
 static void sched_reset_numa(void)
 {
-	int nr_levels, *distances;
-	struct cpumask ***masks;
+	int nr_levels, __rcu *distances;
+	struct cpumask ** __rcu *masks;
 
 	nr_levels = sched_domains_numa_levels;
 	sched_domains_numa_levels = 0;
@@ -2003,7 +2003,7 @@ static void sched_reset_numa(void)
 		int i, j;
 
 		synchronize_rcu();
-		kfree(distances);
+		kfree((void *)distances);
 		for (i = 0; i < nr_levels && masks; i++) {
 			if (!masks[i])
 				continue;
@@ -2011,7 +2011,7 @@ static void sched_reset_numa(void)
 				kfree(masks[i][j]);
 			kfree(masks[i]);
 		}
-		kfree(masks);
+		kfree((void *)masks);
 	}
 	if (sched_domain_topology_saved) {
 		kfree(sched_domain_topology);
-- 
2.25.1