summaryrefslogtreecommitdiff
path: root/kernel/notifier.c
diff options
context:
space:
mode:
authorNadia Derbey <Nadia.Derbey@bull.net>2008-04-29 01:00:45 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-04-29 08:06:13 -0700
commit6546bc4279241e8fa432de1bb63a4f6f791fd669 (patch)
tree308f5c1621b1019a44800622ffc468a372f09434 /kernel/notifier.c
parent91cfb2b4b57816de0c96de417b3238249f0b125f (diff)
downloadlinux-sh-6546bc4279241e8fa432de1bb63a4f6f791fd669.tar.gz
ipc: re-enable msgmni automatic recomputing msgmni if set to negative
The enhancement as asked for by Yasunori: if msgmni is set to a negative value, register it back into the ipcns notifier chain. A new interface has been added to the notification mechanism: notifier_chain_cond_register() registers a notifier block only if not already registered. With that new interface we avoid taking care of the states changes in procfs. Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net> Cc: Yasunori Goto <y-goto@jp.fujitsu.com> Cc: Matt Helsley <matthltc@us.ibm.com> Cc: Mingming Cao <cmm@us.ibm.com> Cc: Pierre Peiffer <pierre.peiffer@bull.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/notifier.c')
-rw-r--r--kernel/notifier.c38
1 files changed, 38 insertions, 0 deletions
diff --git a/kernel/notifier.c b/kernel/notifier.c
index 643360d1bb14..823be11584ef 100644
--- a/kernel/notifier.c
+++ b/kernel/notifier.c
@@ -31,6 +31,21 @@ static int notifier_chain_register(struct notifier_block **nl,
return 0;
}
+static int notifier_chain_cond_register(struct notifier_block **nl,
+ struct notifier_block *n)
+{
+ while ((*nl) != NULL) {
+ if ((*nl) == n)
+ return 0;
+ if (n->priority > (*nl)->priority)
+ break;
+ nl = &((*nl)->next);
+ }
+ n->next = *nl;
+ rcu_assign_pointer(*nl, n);
+ return 0;
+}
+
static int notifier_chain_unregister(struct notifier_block **nl,
struct notifier_block *n)
{
@@ -205,6 +220,29 @@ int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
EXPORT_SYMBOL_GPL(blocking_notifier_chain_register);
/**
+ * blocking_notifier_chain_cond_register - Cond add notifier to a blocking notifier chain
+ * @nh: Pointer to head of the blocking notifier chain
+ * @n: New entry in notifier chain
+ *
+ * Adds a notifier to a blocking notifier chain, only if not already
+ * present in the chain.
+ * Must be called in process context.
+ *
+ * Currently always returns zero.
+ */
+int blocking_notifier_chain_cond_register(struct blocking_notifier_head *nh,
+ struct notifier_block *n)
+{
+ int ret;
+
+ down_write(&nh->rwsem);
+ ret = notifier_chain_cond_register(&nh->head, n);
+ up_write(&nh->rwsem);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(blocking_notifier_chain_cond_register);
+
+/**
* blocking_notifier_chain_unregister - Remove notifier from a blocking notifier chain
* @nh: Pointer to head of the blocking notifier chain
* @n: Entry to remove from notifier chain