lib/percpu_counter.c: __this_cpu_write() doesn't need to be protected by spinlock

__this_cpu_write doesn't need to be protected by spinlock, AS we are doing
per cpu write with preempt disabled.  And another reason to remove
__this_cpu_write outside of spinlock: __percpu_counter_sum is not an
accurate counter.

Signed-off-by: Fan Du <fan.du@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/percpu_counter.c

@@ -80,8 +80,8 @@ void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
 	if (count >= batch || count <= -batch) {
 		raw_spin_lock(&fbc->lock);
 		fbc->count += count;
-		__this_cpu_write(*fbc->counters, 0);
 		raw_spin_unlock(&fbc->lock);
+		__this_cpu_write(*fbc->counters, 0);
 	} else {
 		__this_cpu_write(*fbc->counters, count);
 	}