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Subject[RFC,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:

o 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.

o 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.

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

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

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

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

Please let me know if there are any problems with any of these changes.

Signed-off-by: paulmck@us.ibm.com

---

arch/x86_64/kernel/mce.c | 2 +-
drivers/input/serio/i8042.c | 2 +-
include/asm-i386/kdebug.h | 2 +-
include/asm-ppc64/kdebug.h | 2 +-
include/asm-sparc64/kdebug.h | 2 +-
include/asm-x86_64/kdebug.h | 2 +-
include/linux/list.h | 2 +-
security/keys/key.c | 2 +-
security/keys/process_keys.c | 2 +-
9 files changed, 9 insertions(+), 9 deletions(-)

diff -urpN -X dontdiff linux-2.6.12-rc6-mm1/arch/x86_64/kernel/mce.c linux-2.6.12-rc6-mm1-sksr/arch/x86_64/kernel/mce.c
--- linux-2.6.12-rc6-mm1/arch/x86_64/kernel/mce.c Fri Jun 17 16:40:34 2005
+++ linux-2.6.12-rc6-mm1-sksr/arch/x86_64/kernel/mce.c Fri Jun 17 16:47:51 2005
@@ -411,7 +411,7 @@ static ssize_t mce_read(struct file *fil
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. */

diff -urpN -X dontdiff linux-2.6.12-rc6-mm1/drivers/input/serio/i8042.c linux-2.6.12-rc6-mm1-sksr/drivers/input/serio/i8042.c
--- linux-2.6.12-rc6-mm1/drivers/input/serio/i8042.c Fri Jun 17 16:34:36 2005
+++ linux-2.6.12-rc6-mm1-sksr/drivers/input/serio/i8042.c Fri Jun 17 16:44:26 2005
@@ -396,7 +396,7 @@ static void i8042_stop(struct serio *ser
struct i8042_port *port = serio->port_data;

port->exists = 0;
- synchronize_kernel();
+ synchronize_sched();
port->serio = NULL;
}

diff -urpN -X dontdiff linux-2.6.12-rc6-mm1/include/asm-i386/kdebug.h linux-2.6.12-rc6-mm1-sksr/include/asm-i386/kdebug.h
--- linux-2.6.12-rc6-mm1/include/asm-i386/kdebug.h Tue Mar 1 23:38:25 2005
+++ linux-2.6.12-rc6-mm1-sksr/include/asm-i386/kdebug.h Fri Jun 17 16:50:10 2005
@@ -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;
diff -urpN -X dontdiff linux-2.6.12-rc6-mm1/include/asm-ppc64/kdebug.h linux-2.6.12-rc6-mm1-sksr/include/asm-ppc64/kdebug.h
--- linux-2.6.12-rc6-mm1/include/asm-ppc64/kdebug.h Tue Mar 1 23:38:01 2005
+++ linux-2.6.12-rc6-mm1-sksr/include/asm-ppc64/kdebug.h Fri Jun 17 16:48:29 2005
@@ -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);
diff -urpN -X dontdiff linux-2.6.12-rc6-mm1/include/asm-sparc64/kdebug.h linux-2.6.12-rc6-mm1-sksr/include/asm-sparc64/kdebug.h
--- linux-2.6.12-rc6-mm1/include/asm-sparc64/kdebug.h Tue Mar 1 23:38:32 2005
+++ linux-2.6.12-rc6-mm1-sksr/include/asm-sparc64/kdebug.h Fri Jun 17 16:55:26 2005
@@ -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);
diff -urpN -X dontdiff linux-2.6.12-rc6-mm1/include/asm-x86_64/kdebug.h linux-2.6.12-rc6-mm1-sksr/include/asm-x86_64/kdebug.h
--- linux-2.6.12-rc6-mm1/include/asm-x86_64/kdebug.h Fri Jun 17 16:35:11 2005
+++ linux-2.6.12-rc6-mm1-sksr/include/asm-x86_64/kdebug.h Fri Jun 17 16:48:56 2005
@@ -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;
diff -urpN -X dontdiff linux-2.6.12-rc6-mm1/include/linux/list.h linux-2.6.12-rc6-mm1-sksr/include/linux/list.h
--- linux-2.6.12-rc6-mm1/include/linux/list.h Fri Jun 17 16:41:12 2005
+++ linux-2.6.12-rc6-mm1-sksr/include/linux/list.h Fri Jun 17 16:49:47 2005
@@ -189,7 +189,7 @@ static inline void list_del(struct list_
* 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.
*/
diff -urpN -X dontdiff linux-2.6.12-rc6-mm1/security/keys/key.c linux-2.6.12-rc6-mm1-sksr/security/keys/key.c
--- linux-2.6.12-rc6-mm1/security/keys/key.c Fri Jun 17 16:41:16 2005
+++ linux-2.6.12-rc6-mm1-sksr/security/keys/key.c Fri Jun 17 16:51:46 2005
@@ -980,7 +980,7 @@ void unregister_key_type(struct key_type
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 */
diff -urpN -X dontdiff linux-2.6.12-rc6-mm1/security/keys/process_keys.c linux-2.6.12-rc6-mm1-sksr/security/keys/process_keys.c
--- linux-2.6.12-rc6-mm1/security/keys/process_keys.c Fri Jun 17 16:41:16 2005
+++ linux-2.6.12-rc6-mm1-sksr/security/keys/process_keys.c Fri Jun 17 16:51:26 2005
@@ -234,7 +234,7 @@ static int install_session_keyring(struc
ret = 0;

/* we're using RCU on the pointer */
- synchronize_kernel();
+ synchronize_rcu();
key_put(old);
error:
return ret;
-
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