ipc: invoke the ipcns notifier chain as a work item

Make the memory hotplug chain's mutex held for a shorter time: when memory is
offlined or onlined a work item is added to the global workqueue.  When the
work item is run, it notifies the ipcns notifier chain with the
IPCNS_MEMCHANGED event.

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>

1 files changed, 14 insertions, 1 deletions

diff --git a/ipc/util.c b/ipc/util.c
index 2d545d7144a7..7a5d5e393c4b 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -58,6 +58,14 @@ atomic_t nr_ipc_ns = ATOMIC_INIT(1);
 
 #ifdef CONFIG_MEMORY_HOTPLUG
 
+static void ipc_memory_notifier(struct work_struct *work)
+{
+        ipcns_notify(IPCNS_MEMCHANGED);
+}
+
+static DECLARE_WORK(ipc_memory_wq, ipc_memory_notifier);
+
+
 static int ipc_memory_callback(struct notifier_block *self,
                                 unsigned long action, void *arg)
 {
@@ -67,8 +75,13 @@ static int ipc_memory_callback(struct notifier_block *self,
                 /*
                  * This is done by invoking the ipcns notifier chain with the
                  * IPC_MEMCHANGED event.
+                 * In order not to keep the lock on the hotplug memory chain
+                 * for too long, queue a work item that will, when waken up,
+                 * activate the ipcns notification chain.
+                 * No need to keep several ipc work items on the queue.
                  */
-                ipcns_notify(IPCNS_MEMCHANGED);
+                if (!work_pending(&ipc_memory_wq))
+                        schedule_work(&ipc_memory_wq);
                 break;
         case MEM_GOING_ONLINE:
         case MEM_GOING_OFFLINE: