[PATCH] RCU: clean up a few remaining synchronize_kernel() calls

2.6.12-rc6-mm1 has a few remaining synchronize_kernel()s, some (but not
all) in comments.  This patch changes these synchronize_kernel() calls (and
comments) to synchronize_rcu() or synchronize_sched() as follows:

- arch/x86_64/kernel/mce.c mce_read(): change to synchronize_sched() to
  handle races with machine-check exceptions (synchronize_rcu() would not cut
  it given RCU implementations intended for hardcore realtime use.

- drivers/input/serio/i8042.c i8042_stop(): change to synchronize_sched() to
  handle races with i8042_interrupt() interrupt handler.  Again,
  synchronize_rcu() would not cut it given RCU implementations intended for
  hardcore realtime use.

- include/*/kdebug.h comments: change to synchronize_sched() to handle races
  with NMIs.  As before, synchronize_rcu() would not cut it...

- include/linux/list.h comment: change to synchronize_rcu(), since this
  comment is for list_del_rcu().

- security/keys/key.c unregister_key_type(): change to synchronize_rcu(),
  since this is interacting with RCU read side.

- security/keys/process_keys.c install_session_keyring(): change to
  synchronize_rcu(), since this is interacting with RCU read side.

Signed-off-by: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/x86_64/kernel/mce.c

@@ -411,7 +411,7 @@ static ssize_t mce_read(struct file *filp, char __user *ubuf, size_t usize, loff
 	memset(mcelog.entry, 0, next * sizeof(struct mce));
 	mcelog.next = 0;
 
-	synchronize_kernel();	
+	synchronize_sched();
 
 	/* Collect entries that were still getting written before the synchronize. */
 

drivers/input/serio/i8042.c

@@ -396,7 +396,7 @@ static void i8042_stop(struct serio *serio)
 	struct i8042_port *port = serio->port_data;
 
 	port->exists = 0;
-	synchronize_kernel();
+	synchronize_sched();
 	port->serio = NULL;
 }
 

include/asm-i386/kdebug.h

@@ -18,7 +18,7 @@ struct die_args {
 };
 
 /* Note - you should never unregister because that can race with NMIs.
-   If you really want to do it first unregister - then synchronize_kernel - then free.
+   If you really want to do it first unregister - then synchronize_sched - then free.
   */
 int register_die_notifier(struct notifier_block *nb);
 extern struct notifier_block *i386die_chain;

include/asm-ppc64/kdebug.h

@@ -17,7 +17,7 @@ struct die_args {
 
 /*
    Note - you should never unregister because that can race with NMIs.
-   If you really want to do it first unregister - then synchronize_kernel -
+   If you really want to do it first unregister - then synchronize_sched -
    then free.
  */
 int register_die_notifier(struct notifier_block *nb);

include/asm-sparc64/kdebug.h

@@ -16,7 +16,7 @@ struct die_args {
 };
 
 /* Note - you should never unregister because that can race with NMIs.
- * If you really want to do it first unregister - then synchronize_kernel
+ * If you really want to do it first unregister - then synchronize_sched
  * - then free.
  */
 int register_die_notifier(struct notifier_block *nb);

include/asm-x86_64/kdebug.h

@@ -14,7 +14,7 @@ struct die_args {
 }; 
 
 /* Note - you should never unregister because that can race with NMIs.
-   If you really want to do it first unregister - then synchronize_kernel - then free. 
+   If you really want to do it first unregister - then synchronize_sched - then free.
   */
 int register_die_notifier(struct notifier_block *nb);
 extern struct notifier_block *die_chain;

include/linux/list.h

@@ -185,7 +185,7 @@ static inline void list_del(struct list_head *entry)
  * list_for_each_entry_rcu().
  *
  * Note that the caller is not permitted to immediately free
- * the newly deleted entry.  Instead, either synchronize_kernel()
+ * the newly deleted entry.  Instead, either synchronize_rcu()
  * or call_rcu() must be used to defer freeing until an RCU
  * grace period has elapsed.
  */

security/keys/key.c

@@ -980,7 +980,7 @@ void unregister_key_type(struct key_type *ktype)
 	spin_unlock(&key_serial_lock);
 
 	/* make sure everyone revalidates their keys */
-	synchronize_kernel();
+	synchronize_rcu();
 
 	/* we should now be able to destroy the payloads of all the keys of
 	 * this type with impunity */

security/keys/process_keys.c

@@ -234,7 +234,7 @@ static int install_session_keyring(struct task_struct *tsk,
 	ret = 0;
 
 	/* we're using RCU on the pointer */
-	synchronize_kernel();
+	synchronize_rcu();
 	key_put(old);
  error:
 	return ret;