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From:   Joel Fernandes <joel@joelfernandes.org>
To:     linux-kernel@vger.kernel.org
Cc:     kernel-team@android.com,
        "Joel Fernandes (Google)" <joel@joelfernandes.org>,
        Boqun Feng <boqun.feng@gmail.com>,
        Byungchul Park <byungchul.park@lge.com>,
        Ingo Molnar <mingo@redhat.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Glexiner <tglx@linutronix.de>,
        Tom Zanussi <tom.zanussi@linux.intel.com>
Subject: [PATCH v12 1/3] lockdep: use this_cpu_ptr instead of get_cpu_var stats
Date:   Mon, 30 Jul 2018 15:24:21 -0700
Message-Id: <20180730222423.196630-2-joel@joelfernandes.org>
In-Reply-To: <20180730222423.196630-1-joel@joelfernandes.org>
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From: "Joel Fernandes (Google)" <joel@joelfernandes.org>

get_cpu_var disables preemption which has the potential to call into the
preemption disable trace points causing some complications. There's also
no need to disable preemption in uses of get_lock_stats anyway since
preempt is already disabled. So lets simplify the code.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 kernel/locking/lockdep.c | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 5fa4d3138bf1..fbbb79d5cfa0 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -248,12 +248,7 @@ void clear_lock_stats(struct lock_class *class)
 
 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
 {
-	return &get_cpu_var(cpu_lock_stats)[class - lock_classes];
-}
-
-static void put_lock_stats(struct lock_class_stats *stats)
-{
-	put_cpu_var(cpu_lock_stats);
+	return &this_cpu_ptr(cpu_lock_stats)[class - lock_classes];
 }
 
 static void lock_release_holdtime(struct held_lock *hlock)
@@ -271,7 +266,6 @@ static void lock_release_holdtime(struct held_lock *hlock)
 		lock_time_inc(&stats->read_holdtime, holdtime);
 	else
 		lock_time_inc(&stats->write_holdtime, holdtime);
-	put_lock_stats(stats);
 }
 #else
 static inline void lock_release_holdtime(struct held_lock *hlock)
@@ -4090,7 +4084,6 @@ __lock_contended(struct lockdep_map *lock, unsigned long ip)
 		stats->contending_point[contending_point]++;
 	if (lock->cpu != smp_processor_id())
 		stats->bounces[bounce_contended + !!hlock->read]++;
-	put_lock_stats(stats);
 }
 
 static void
@@ -4138,7 +4131,6 @@ __lock_acquired(struct lockdep_map *lock, unsigned long ip)
 	}
 	if (lock->cpu != cpu)
 		stats->bounces[bounce_acquired + !!hlock->read]++;
-	put_lock_stats(stats);
 
 	lock->cpu = cpu;
 	lock->ip = ip;
-- 
2.18.0.345.g5c9ce644c3-goog