locking/lockdep: Shrink struct lock_class_key

Peter Zijlstra · Ingo Molnar · commit 28d49e282665 · 2019-02-28T07:55:53.000+01:00
Shrink struct lock_class_key; we never store anything in subkeys[], we
only use the addresses.

Signed-off-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Cc: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Paul E. McKenney &lt;paulmck@linux.vnet.ibm.com&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Will Deacon &lt;will.deacon@arm.com&gt;
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
@@ -58,8 +58,10 @@ struct lockdep_subclass_key {
 
 /* hash_entry is used to keep track of dynamically allocated keys. */
 struct lock_class_key {
-	struct hlist_node		hash_entry;
-	struct lockdep_subclass_key	subkeys[MAX_LOCKDEP_SUBCLASSES];
+	union {
+		struct hlist_node		hash_entry;
+		struct lockdep_subclass_key	subkeys[MAX_LOCKDEP_SUBCLASSES];
+	};
 };
 
 extern struct lock_class_key __lockdep_no_validate__;
