linux-kernel - [PATCH v2 1/4] sched/cpufreq: Annotate cpufreq_update_util_data pointer with _

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Date:   Wed, 20 Mar 2019 20:34:23 -0400
From:   "Joel Fernandes (Google)" <joel@...lfernandes.org>
To:     linux-kernel@...r.kernel.org
Cc:     "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        "Paul E . McKenney" <paulmck@...ux.ibm.com>,
        Ingo Molnar <mingo@...hat.com>,
        Josh Triplett <josh@...htriplett.org>, keescook@...omium.org,
        kernel-hardening@...ts.openwall.com, kernel-team@...roid.com,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Peter Zijlstra <peterz@...radead.org>, rcu@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH v2 1/4] sched/cpufreq: Annotate cpufreq_update_util_data pointer with __rcu

Recently I added an RCU annotation check to rcu_assign_pointer(). All
pointers assigned to RCU protected data are to be annotated with __rcu
inorder to be able to use rcu_assign_pointer() similar to checks in
other RCU APIs.

This resulted in a sparse error: kernel//sched/cpufreq.c:41:9: sparse:
error: incompatible types in comparison expression (different address
spaces)

Fix this by annotating cpufreq_update_util_data pointer with __rcu. This
will also help sparse catch any future RCU misuage bugs.

[From an RCU perspective]
Reviewed-by: Paul E. McKenney <paulmck@...ux.ibm.com>
Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
---
 kernel/sched/cpufreq.c | 2 +-
 kernel/sched/sched.h   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/cpufreq.c b/kernel/sched/cpufreq.c
index 835671f0f917..b5dcd1d83c7f 100644
--- a/kernel/sched/cpufreq.c
+++ b/kernel/sched/cpufreq.c
@@ -7,7 +7,7 @@
  */
 #include "sched.h"
 
-DEFINE_PER_CPU(struct update_util_data *, cpufreq_update_util_data);
+DEFINE_PER_CPU(struct update_util_data __rcu *, cpufreq_update_util_data);
 
 /**
  * cpufreq_add_update_util_hook - Populate the CPU's update_util_data pointer.
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index efa686eeff26..713715dd00cf 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2185,7 +2185,7 @@ static inline u64 irq_time_read(int cpu)
 #endif /* CONFIG_IRQ_TIME_ACCOUNTING */
 
 #ifdef CONFIG_CPU_FREQ
-DECLARE_PER_CPU(struct update_util_data *, cpufreq_update_util_data);
+DECLARE_PER_CPU(struct update_util_data __rcu *, cpufreq_update_util_data);
 
 /**
  * cpufreq_update_util - Take a note about CPU utilization changes.
-- 
2.21.0.225.g810b269d1ac-goog