[PATCH 05/08]

This patch makes 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 <[EMAIL PROTECTED]>

---
 ipc/util.c |   15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

Index: linux-2.6.24-mm1/ipc/util.c
===================================================================
--- linux-2.6.24-mm1.orig/ipc/util.c    2008-02-08 08:15:35.000000000 +0100
+++ linux-2.6.24-mm1/ipc/util.c 2008-02-08 14:14:03.000000000 +0100
@@ -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 no
                /*
                 * 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:

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