core: Replace __get_cpu_var with __this_cpu_read if not used for an address.

__get_cpu_var() can be replaced with this_cpu_read and will then use a
single read instruction with implied address calculation to access the
correct per cpu instance.

However, the address of a per cpu variable passed to __this_cpu_read()
cannot be determined (since it's an implied address conversion through
segment prefixes).  Therefore apply this only to uses of __get_cpu_var
where the address of the variable is not used.

Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Hugh Dickins <hughd@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 3b159c5991b7..e05e27de67df 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1282,7 +1282,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
                         attach_pid(p, PIDTYPE_SID, task_session(current));
                         list_add_tail(&p->sibling, &p->real_parent->children);
                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
-                        __get_cpu_var(process_counts)++;
+                        __this_cpu_inc(process_counts);
                 }
                 attach_pid(p, PIDTYPE_PID, pid);
                 nr_threads++;