rapidio/rio_cm: avoid GFP_KERNEL in atomic context

As reported by Alexey Khoroshilov (https://lkml.org/lkml/2016/9/9/737):
riocm_send_close() is called from rio_cm_shutdown() under
spin_lock_bh(idr_lock), but riocm_send_close() uses a GFP_KERNEL
allocation.

Fix by taking riocm_send_close() outside of spinlock protected code.

[akpm@linux-foundation.org: remove unneeded `if (!list_empty())']
Link: http://lkml.kernel.org/r/20160915175402.10122-1-alexandre.bounine@idt.comSigned-off-by: NAlexandre Bounine <alexandre.bounine@idt.com>
Reported-by: NAlexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/rapidio/rio_cm.c

@@ -2247,17 +2247,30 @@ static int rio_cm_shutdown(struct notifier_block *nb, unsigned long code,
 {
 	struct rio_channel *ch;
 	unsigned int i;
+	LIST_HEAD(list);
 
 	riocm_debug(EXIT, ".");
 
+	/*
+	 * If there are any channels left in connected state send
+	 * close notification to the connection partner.
+	 * First build a list of channels that require a closing
+	 * notification because function riocm_send_close() should
+	 * be called outside of spinlock protected code.
+	 */
 	spin_lock_bh(&idr_lock);
 	idr_for_each_entry(&ch_idr, ch, i) {
+		if (ch->state == RIO_CM_CONNECTED) {
 			riocm_debug(EXIT, "close ch %d", ch->id);
-		if (ch->state == RIO_CM_CONNECTED)
-			riocm_send_close(ch);
+			idr_remove(&ch_idr, ch->id);
+			list_add(&ch->ch_node, &list);
+		}
 	}
 	spin_unlock_bh(&idr_lock);
 
+	list_for_each_entry(ch, &list, ch_node)
+		riocm_send_close(ch);
+
 	return NOTIFY_DONE;
 }