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Message-ID: <5885405.DvuYhMxLoT@rjwysocki.net>
Date: Thu, 06 Mar 2025 17:49:20 +0100
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>, Lukasz Luba <lukasz.luba@....com>
Cc: LKML <linux-kernel@...r.kernel.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Subject: [PATCH v2] PM: EM: Address RCU-related sparse warnings
From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
The usage of __rcu in the Energy Model code is quite inconsistent
which causes the following sparse warnings to trigger:
kernel/power/energy_model.c:169:15: warning: incorrect type in assignment (different address spaces)
kernel/power/energy_model.c:169:15: expected struct em_perf_table [noderef] __rcu *table
kernel/power/energy_model.c:169:15: got struct em_perf_table *
kernel/power/energy_model.c:171:9: warning: incorrect type in argument 1 (different address spaces)
kernel/power/energy_model.c:171:9: expected struct callback_head *head
kernel/power/energy_model.c:171:9: got struct callback_head [noderef] __rcu *
kernel/power/energy_model.c:171:9: warning: cast removes address space '__rcu' of expression
kernel/power/energy_model.c:182:19: warning: incorrect type in argument 1 (different address spaces)
kernel/power/energy_model.c:182:19: expected struct kref *kref
kernel/power/energy_model.c:182:19: got struct kref [noderef] __rcu *
kernel/power/energy_model.c:200:15: warning: incorrect type in assignment (different address spaces)
kernel/power/energy_model.c:200:15: expected struct em_perf_table [noderef] __rcu *table
kernel/power/energy_model.c:200:15: got void *[assigned] _res
kernel/power/energy_model.c:204:20: warning: incorrect type in argument 1 (different address spaces)
kernel/power/energy_model.c:204:20: expected struct kref *kref
kernel/power/energy_model.c:204:20: got struct kref [noderef] __rcu *
kernel/power/energy_model.c:320:19: warning: incorrect type in argument 1 (different address spaces)
kernel/power/energy_model.c:320:19: expected struct kref *kref
kernel/power/energy_model.c:320:19: got struct kref [noderef] __rcu *
kernel/power/energy_model.c:325:45: warning: incorrect type in argument 2 (different address spaces)
kernel/power/energy_model.c:325:45: expected struct em_perf_state *table
kernel/power/energy_model.c:325:45: got struct em_perf_state [noderef] __rcu *
kernel/power/energy_model.c:425:45: warning: incorrect type in argument 3 (different address spaces)
kernel/power/energy_model.c:425:45: expected struct em_perf_state *table
kernel/power/energy_model.c:425:45: got struct em_perf_state [noderef] __rcu *
kernel/power/energy_model.c:442:15: warning: incorrect type in argument 1 (different address spaces)
kernel/power/energy_model.c:442:15: expected void const *objp
kernel/power/energy_model.c:442:15: got struct em_perf_table [noderef] __rcu *[assigned] em_table
kernel/power/energy_model.c:626:55: warning: incorrect type in argument 2 (different address spaces)
kernel/power/energy_model.c:626:55: expected struct em_perf_state *table
kernel/power/energy_model.c:626:55: got struct em_perf_state [noderef] __rcu *
kernel/power/energy_model.c:681:16: warning: incorrect type in assignment (different address spaces)
kernel/power/energy_model.c:681:16: expected struct em_perf_state *new_ps
kernel/power/energy_model.c:681:16: got struct em_perf_state [noderef] __rcu *
kernel/power/energy_model.c:699:37: warning: incorrect type in argument 2 (different address spaces)
kernel/power/energy_model.c:699:37: expected struct em_perf_state *table
kernel/power/energy_model.c:699:37: got struct em_perf_state [noderef] __rcu *
kernel/power/energy_model.c:733:38: warning: incorrect type in argument 3 (different address spaces)
kernel/power/energy_model.c:733:38: expected struct em_perf_state *table
kernel/power/energy_model.c:733:38: got struct em_perf_state [noderef] __rcu *
kernel/power/energy_model.c:855:53: warning: dereference of noderef expression
kernel/power/energy_model.c:864:32: warning: dereference of noderef expression
This is because the __rcu annotation for sparse is only applicable to
pointers that need rcu_dereference() or equivalent for protection, which
basically means pointers assigned with rcu_assign_pointer().
Make all of the above sparse warnings go away by cleaning up the usage
of __rcu and using rcu_dereference_protected() where applicable.
Cc: All applicable <stable@...r.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
This replaces
https://lore.kernel.org/linux-pm/1929404.tdWV9SEqCh@rjwysocki.net/
and
https://lore.kernel.org/linux-pm/13728396.uLZWGnKmhe@rjwysocki.net/
---
include/linux/energy_model.h | 12 ++++++------
kernel/power/energy_model.c | 39 ++++++++++++++++++++-------------------
2 files changed, 26 insertions(+), 25 deletions(-)
--- a/include/linux/energy_model.h
+++ b/include/linux/energy_model.h
@@ -167,13 +167,13 @@
struct em_perf_domain *em_cpu_get(int cpu);
struct em_perf_domain *em_pd_get(struct device *dev);
int em_dev_update_perf_domain(struct device *dev,
- struct em_perf_table __rcu *new_table);
+ struct em_perf_table *new_table);
int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
const struct em_data_callback *cb,
const cpumask_t *cpus, bool microwatts);
void em_dev_unregister_perf_domain(struct device *dev);
-struct em_perf_table __rcu *em_table_alloc(struct em_perf_domain *pd);
-void em_table_free(struct em_perf_table __rcu *table);
+struct em_perf_table *em_table_alloc(struct em_perf_domain *pd);
+void em_table_free(struct em_perf_table *table);
int em_dev_compute_costs(struct device *dev, struct em_perf_state *table,
int nr_states);
int em_dev_update_chip_binning(struct device *dev);
@@ -373,14 +373,14 @@
return 0;
}
static inline
-struct em_perf_table __rcu *em_table_alloc(struct em_perf_domain *pd)
+struct em_perf_table *em_table_alloc(struct em_perf_domain *pd)
{
return NULL;
}
-static inline void em_table_free(struct em_perf_table __rcu *table) {}
+static inline void em_table_free(struct em_perf_table *table) {}
static inline
int em_dev_update_perf_domain(struct device *dev,
- struct em_perf_table __rcu *new_table)
+ struct em_perf_table *new_table)
{
return -EINVAL;
}
--- a/kernel/power/energy_model.c
+++ b/kernel/power/energy_model.c
@@ -163,12 +163,8 @@
static void em_release_table_kref(struct kref *kref)
{
- struct em_perf_table __rcu *table;
-
/* It was the last owner of this table so we can free */
- table = container_of(kref, struct em_perf_table, kref);
-
- kfree_rcu(table, rcu);
+ kfree_rcu(container_of(kref, struct em_perf_table, kref), rcu);
}
/**
@@ -177,7 +173,7 @@
*
* No return values.
*/
-void em_table_free(struct em_perf_table __rcu *table)
+void em_table_free(struct em_perf_table *table)
{
kref_put(&table->kref, em_release_table_kref);
}
@@ -190,9 +186,9 @@
* has a user.
* Returns allocated table or NULL.
*/
-struct em_perf_table __rcu *em_table_alloc(struct em_perf_domain *pd)
+struct em_perf_table *em_table_alloc(struct em_perf_domain *pd)
{
- struct em_perf_table __rcu *table;
+ struct em_perf_table *table;
int table_size;
table_size = sizeof(struct em_perf_state) * pd->nr_perf_states;
@@ -300,9 +296,9 @@
* Return 0 on success or an error code on failure.
*/
int em_dev_update_perf_domain(struct device *dev,
- struct em_perf_table __rcu *new_table)
+ struct em_perf_table *new_table)
{
- struct em_perf_table __rcu *old_table;
+ struct em_perf_table *old_table;
struct em_perf_domain *pd;
if (!dev)
@@ -319,7 +315,8 @@
kref_get(&new_table->kref);
- old_table = pd->em_table;
+ old_table = rcu_dereference_protected(pd->em_table,
+ lockdep_is_held(&em_pd_mutex));
rcu_assign_pointer(pd->em_table, new_table);
em_cpufreq_update_efficiencies(dev, new_table->state);
@@ -392,7 +389,7 @@
const cpumask_t *cpus,
unsigned long flags)
{
- struct em_perf_table __rcu *em_table;
+ struct em_perf_table *em_table;
struct em_perf_domain *pd;
struct device *cpu_dev;
int cpu, ret, num_cpus;
@@ -552,6 +549,7 @@
const struct em_data_callback *cb,
const cpumask_t *cpus, bool microwatts)
{
+ struct em_perf_table *em_table;
unsigned long cap, prev_cap = 0;
unsigned long flags = 0;
int cpu, ret;
@@ -624,7 +622,9 @@
dev->em_pd->min_perf_state = 0;
dev->em_pd->max_perf_state = nr_states - 1;
- em_cpufreq_update_efficiencies(dev, dev->em_pd->em_table->state);
+ em_table = rcu_dereference_protected(dev->em_pd->em_table,
+ lockdep_is_held(&em_pd_mutex));
+ em_cpufreq_update_efficiencies(dev, em_table->state);
em_debug_create_pd(dev);
dev_info(dev, "EM: created perf domain\n");
@@ -661,7 +661,8 @@
mutex_lock(&em_pd_mutex);
em_debug_remove_pd(dev);
- em_table_free(dev->em_pd->em_table);
+ em_table_free(rcu_dereference_protected(dev->em_pd->em_table,
+ lockdep_is_held(&em_pd_mutex)));
kfree(dev->em_pd);
dev->em_pd = NULL;
@@ -669,9 +670,9 @@
}
EXPORT_SYMBOL_GPL(em_dev_unregister_perf_domain);
-static struct em_perf_table __rcu *em_table_dup(struct em_perf_domain *pd)
+static struct em_perf_table *em_table_dup(struct em_perf_domain *pd)
{
- struct em_perf_table __rcu *em_table;
+ struct em_perf_table *em_table;
struct em_perf_state *ps, *new_ps;
int ps_size;
@@ -693,7 +694,7 @@
}
static int em_recalc_and_update(struct device *dev, struct em_perf_domain *pd,
- struct em_perf_table __rcu *em_table)
+ struct em_perf_table *em_table)
{
int ret;
@@ -723,7 +724,7 @@
static void em_adjust_new_capacity(struct device *dev,
struct em_perf_domain *pd)
{
- struct em_perf_table __rcu *em_table;
+ struct em_perf_table *em_table;
em_table = em_table_dup(pd);
if (!em_table) {
@@ -814,7 +815,7 @@
*/
int em_dev_update_chip_binning(struct device *dev)
{
- struct em_perf_table __rcu *em_table;
+ struct em_perf_table *em_table;
struct em_perf_domain *pd;
int i, ret;
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