seqcount: Rename write_seqcount_barrier()

I'll shortly be introducing another seqcount primitive that's useful
to provide ordering semantics and would like to use the
write_seqcount_barrier() name for that.

Seeing how there's only one user of the current primitive, lets rename
it to invalidate, as that appears what its doing.

While there, employ lockdep_assert_held() instead of
assert_spin_locked() to not generate debug code for regular kernels.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: ktkhai@parallels.com
Cc: rostedt@goodmis.org
Cc: juri.lelli@gmail.com
Cc: pang.xunlei@linaro.org
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: wanpeng.li@linux.intel.com
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: umgwanakikbuti@gmail.com
Link: http://lkml.kernel.org/r/20150611124743.279926217@infradead.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index 5f68d0a..c07e3a5 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -266,13 +266,13 @@
 }
 
 /**
- * write_seqcount_barrier - invalidate in-progress read-side seq operations
+ * write_seqcount_invalidate - invalidate in-progress read-side seq operations
  * @s: pointer to seqcount_t
  *
- * After write_seqcount_barrier, no read-side seq operations will complete
+ * After write_seqcount_invalidate, no read-side seq operations will complete
  * successfully and see data older than this.
  */
-static inline void write_seqcount_barrier(seqcount_t *s)
+static inline void write_seqcount_invalidate(seqcount_t *s)
 {
 	smp_wmb();
 	s->sequence+=2;