path: root/ipc/namespace.c
diff options
authorNadia Derbey <Nadia.Derbey@bull.net>2008-04-29 01:00:42 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-04-29 08:06:12 -0700
commitb6b337ad1c1d6fe11b09b35d75464b84b3e11f07 (patch)
treedf174a23a827cc43db76900d1ddbbef3ac9ddc90 /ipc/namespace.c
parent0c40ba4fd64f98e7a5cba8ffaedbd68642a85700 (diff)
ipc: recompute msgmni on memory add / remove
Introduce the registration of a callback routine that recomputes msg_ctlmni upon memory add / remove. A single notifier block is registered in the hotplug memory chain for all the ipc namespaces. Since the ipc namespaces are not linked together, they have their own notification chain: one notifier_block is defined per ipc namespace. Each time an ipc namespace is created (removed) it registers (unregisters) its notifier block in (from) the ipcns chain. The callback routine registered in the memory chain invokes the ipcns notifier chain with the IPCNS_LOWMEM event. Each callback routine registered in the ipcns namespace, in turn, recomputes msgmni for the owning namespace. 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 'ipc/namespace.c')
1 files changed, 11 insertions, 0 deletions
diff --git a/ipc/namespace.c b/ipc/namespace.c
index fe3c97aa99d..f7a35be2e77 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -26,6 +26,8 @@ static struct ipc_namespace *clone_ipc_ns(struct ipc_namespace *old_ns)
+ register_ipcns_notifier(ns);
return ns;
@@ -81,6 +83,15 @@ void free_ipc_ns(struct kref *kref)
struct ipc_namespace *ns;
ns = container_of(kref, struct ipc_namespace, kref);
+ /*
+ * Unregistering the hotplug notifier at the beginning guarantees
+ * that the ipc namespace won't be freed while we are inside the
+ * callback routine. Since the blocking_notifier_chain_XXX routines
+ * hold a rw lock on the notifier list, unregister_ipcns_notifier()
+ * won't take the rw lock before blocking_notifier_call_chain() has
+ * released the rd lock.
+ */
+ unregister_ipcns_notifier(ns);