The patch titled
IPMI: Fix some RCU problems
has been removed from the -mm tree. Its filename was
ipmi-fix-some-rcu-problems.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
Subject: IPMI: Fix some RCU problems
From: Corey Minyard <minyard@xxxxxxx>
Fix some RCU problem pointed out by Paul McKenney of IBM. These are:
The wholesale move of the command receivers list into a new list was not
safe because the list will point to the new tail during a traversal, so the
traversal will never end on a reader if this happens during a read.
Memory barriers were needed to handle proper ordering of the setting of the
IPMI interface as valid. Readers might not see proper ordering of data
otherwise.
In ipmi_smi_watcher_register(), the use of the _rcu suffix on the list is
unnecessary.
This require the list_splice_init_rcu() patch previously posted.
Signed-off-by: Corey Minyard <minyard@xxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/char/ipmi/ipmi_msghandler.c | 29 +++++++++++++++++++-------
1 file changed, 22 insertions(+), 7 deletions(-)
diff -puN drivers/char/ipmi/ipmi_msghandler.c~ipmi-fix-some-rcu-problems drivers/char/ipmi/ipmi_msghandler.c
--- a/drivers/char/ipmi/ipmi_msghandler.c~ipmi-fix-some-rcu-problems
+++ a/drivers/char/ipmi/ipmi_msghandler.c
@@ -406,13 +406,14 @@ static void clean_up_interface_data(ipmi
free_smi_msg_list(&intf->waiting_msgs);
free_recv_msg_list(&intf->waiting_events);
- /* Wholesale remove all the entries from the list in the
- * interface and wait for RCU to know that none are in use. */
+ /*
+ * Wholesale remove all the entries from the list in the
+ * interface and wait for RCU to know that none are in use.
+ */
mutex_lock(&intf->cmd_rcvrs_mutex);
- list_add_rcu(&list, &intf->cmd_rcvrs);
- list_del_rcu(&intf->cmd_rcvrs);
+ INIT_LIST_HEAD(&list);
+ list_splice_init_rcu(&intf->cmd_rcvrs, &list, synchronize_rcu);
mutex_unlock(&intf->cmd_rcvrs_mutex);
- synchronize_rcu();
list_for_each_entry_safe(rcvr, rcvr2, &list, link)
kfree(rcvr);
@@ -451,7 +452,7 @@ int ipmi_smi_watcher_register(struct ipm
mutex_lock(&ipmi_interfaces_mutex);
/* Build a list of things to deliver. */
- list_for_each_entry_rcu(intf, &ipmi_interfaces, link) {
+ list_for_each_entry(intf, &ipmi_interfaces, link) {
if (intf->intf_num == -1)
continue;
e = kmalloc(sizeof(*e), GFP_KERNEL);
@@ -2760,9 +2761,15 @@ int ipmi_register_smi(struct ipmi_smi_ha
synchronize_rcu();
kref_put(&intf->refcount, intf_free);
} else {
- /* After this point the interface is legal to use. */
+ /*
+ * Keep memory order straight for RCU readers. Make
+ * sure everything else is committed to memory before
+ * setting intf_num to mark the interface valid.
+ */
+ smp_wmb();
intf->intf_num = i;
mutex_unlock(&ipmi_interfaces_mutex);
+ /* After this point the interface is legal to use. */
call_smi_watchers(i, intf->si_dev);
mutex_unlock(&smi_watchers_mutex);
}
@@ -3923,6 +3930,14 @@ static void send_panic_events(char *str)
/* Interface was not ready yet. */
continue;
+ /*
+ * intf_num is used as an marker to tell if the
+ * interface is valid. Thus we need a read barrier to
+ * make sure data fetched before checking intf_num
+ * won't be used.
+ */
+ smp_rmb();
+
/* First job here is to figure out where to send the
OEM events. There's no way in IPMI to send OEM
events using an event send command, so we have to
_
Patches currently in -mm which might be from minyard@xxxxxxx are
origin.patch
add-an-rcu-version-of-list-splicing.patch
sysctl-ipmi-remove-unnecessary-insert_at_head-flag.patch
sysctl-remove-insert_at_head-from-register_sysctl.patch
-
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