wimax/i2400m: queue device's report until the driver is ready for them

The i2400m might start sending reports to the driver before it is done
setting up all the infrastructure needed for handling them.

Currently we were just dropping them when the driver wasn't ready and
that is bad in certain situations, as the sync between the driver's
idea of the device's state and the device's state dissapears.

This changes that by implementing a queue for handling
reports. Incoming reports are appended to it and a workstruct is woken
to process the list of queued reports.

When the device is not yet ready to handle them, the workstruct is not
woken, but at soon as the device becomes ready again, the queue is
processed.

As a consequence of this, i2400m_queue_work() is no longer used, and
thus removed.

Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>

1 files changed, 113 insertions, 29 deletions

diff --git a/drivers/net/wimax/i2400m/rx.c b/drivers/net/wimax/i2400m/rx.c
index 82c200ad9fdc..64a44ca00675 100644
--- a/drivers/net/wimax/i2400m/rx.c
+++ b/drivers/net/wimax/i2400m/rx.c
@@ -158,29 +158,104 @@ struct i2400m_report_hook_args {
 	struct sk_buff *skb_rx;
 	const struct i2400m_l3l4_hdr *l3l4_hdr;
 	size_t size;
+	struct list_head list_node;
 };
 
 
 /*
  * Execute i2400m_report_hook in a workqueue
  *
- * Unpacks arguments from the deferred call, executes it and then
- * drops the references.
+ * Goes over the list of queued reports in i2400m->rx_reports and
+ * processes them.
  *
- * Obvious NOTE: References are needed because we are a separate
- *     thread; otherwise the buffer changes under us because it is
- *     released by the original caller.
+ * NOTE: refcounts on i2400m are not needed because we flush the
+ *     workqueue this runs on (i2400m->work_queue) before destroying
+ *     i2400m.
  */
-static
 void i2400m_report_hook_work(struct work_struct *ws)
 {
-	struct i2400m_work *iw =
-		container_of(ws, struct i2400m_work, ws);
-	struct i2400m_report_hook_args *args = (void *) iw->pl;
-	i2400m_report_hook(iw->i2400m, args->l3l4_hdr, args->size);
-	kfree_skb(args->skb_rx);
-	i2400m_put(iw->i2400m);
-	kfree(iw);
+	struct i2400m *i2400m = container_of(ws, struct i2400m, rx_report_ws);
+	struct device *dev = i2400m_dev(i2400m);
+	struct i2400m_report_hook_args *args, *args_next;
+	LIST_HEAD(list);
+	unsigned long flags;
+
+	while (1) {
+		spin_lock_irqsave(&i2400m->rx_lock, flags);
+		list_splice_init(&i2400m->rx_reports, &list);
+		spin_unlock_irqrestore(&i2400m->rx_lock, flags);
+		if (list_empty(&list))
+			break;
+		else
+			d_printf(1, dev, "processing queued reports\n");
+		list_for_each_entry_safe(args, args_next, &list, list_node) {
+			d_printf(2, dev, "processing queued report %p\n", args);
+			i2400m_report_hook(i2400m, args->l3l4_hdr, args->size);
+			kfree_skb(args->skb_rx);
+			list_del(&args->list_node);
+			kfree(args);
+		}
+	}
+}
+
+
+/*
+ * Flush the list of queued reports
+ */
+static
+void i2400m_report_hook_flush(struct i2400m *i2400m)
+{
+	struct device *dev = i2400m_dev(i2400m);
+	struct i2400m_report_hook_args *args, *args_next;
+	LIST_HEAD(list);
+	unsigned long flags;
+
+	d_printf(1, dev, "flushing queued reports\n");
+	spin_lock_irqsave(&i2400m->rx_lock, flags);
+	list_splice_init(&i2400m->rx_reports, &list);
+	spin_unlock_irqrestore(&i2400m->rx_lock, flags);
+	list_for_each_entry_safe(args, args_next, &list, list_node) {
+		d_printf(2, dev, "flushing queued report %p\n", args);
+		kfree_skb(args->skb_rx);
+		list_del(&args->list_node);
+		kfree(args);
+	}
+}
+
+
+/*
+ * Queue a report for later processing
+ *
+ * @i2400m: device descriptor
+ * @skb_rx: skb that contains the payload (for reference counting)
+ * @l3l4_hdr: pointer to the control
+ * @size: size of the message
+ */
+static
+void i2400m_report_hook_queue(struct i2400m *i2400m, struct sk_buff *skb_rx,
+			      const void *l3l4_hdr, size_t size)
+{
+	struct device *dev = i2400m_dev(i2400m);
+	unsigned long flags;
+	struct i2400m_report_hook_args *args;
+
+	args = kzalloc(sizeof(*args), GFP_NOIO);
+	if (args) {
+		args->skb_rx = skb_get(skb_rx);
+		args->l3l4_hdr = l3l4_hdr;
+		args->size = size;
+		spin_lock_irqsave(&i2400m->rx_lock, flags);
+		list_add_tail(&args->list_node, &i2400m->rx_reports);
+		spin_unlock_irqrestore(&i2400m->rx_lock, flags);
+		d_printf(2, dev, "queued report %p\n", args);
+		rmb();		/* see i2400m->ready's documentation  */
+		if (likely(i2400m->ready))	/* only send if up */
+			queue_work(i2400m->work_queue, &i2400m->rx_report_ws);
+	} else  {
+		if (printk_ratelimit())
+			dev_err(dev, "%s:%u: Can't allocate %zu B\n",
+				__func__, __LINE__, sizeof(*args));
+	}
 }
 
 
@@ -294,22 +369,29 @@ void i2400m_rx_ctl(struct i2400m *i2400m, struct sk_buff *skb_rx,
 		 msg_type, size);
 	d_dump(2, dev, l3l4_hdr, size);
 	if (msg_type & I2400M_MT_REPORT_MASK) {
-		/* These hooks have to be ran serialized; as well, the
-		 * handling might force the execution of commands, and
-		 * that might cause reentrancy issues with
-		 * bus-specific subdrivers and workqueues. So we run
-		 * it in a separate workqueue. */
-		struct i2400m_report_hook_args args = {
-			.skb_rx = skb_rx,
-			.l3l4_hdr = l3l4_hdr,
-			.size = size
-		};
-		rmb();		/* see i2400m->ready's documentation  */
-		if (likely(i2400m->ready)) {	/* only send if up */
-			skb_get(skb_rx);
-			i2400m_queue_work(i2400m, i2400m_report_hook_work,
-					  GFP_KERNEL, &args, sizeof(args));
-		}
+		/*
+		 * Process each report
+		 *
+		 * - has to be ran serialized as well
+		 *
+		 * - the handling might force the execution of
+		 *   commands. That might cause reentrancy issues with
+		 *   bus-specific subdrivers and workqueues, so the we
+		 *   run it in a separate workqueue.
+		 *
+		 * - when the driver is not yet ready to handle them,
+		 *   they are queued and at some point the queue is
+		 *   restarted [NOTE: we can't queue SKBs directly, as
+		 *   this might be a piece of a SKB, not the whole
+		 *   thing, and this is cheaper than cloning the
+		 *   SKB].
+		 *
+		 * Note we don't do refcounting for the device
+		 * structure; this is because before destroying
+		 * 'i2400m', we make sure to flush the
+		 * i2400m->work_queue, so there are no issues.
+		 */
+		i2400m_report_hook_queue(i2400m, skb_rx, l3l4_hdr, size);
 		if (unlikely(i2400m->trace_msg_from_user))
 			wimax_msg(&i2400m->wimax_dev, "echo",
 				  l3l4_hdr, size, GFP_KERNEL);
@@ -1281,4 +1363,6 @@ void i2400m_rx_release(struct i2400m *i2400m)
 		kfree(i2400m->rx_roq[0].log);
 		kfree(i2400m->rx_roq);
 	}
+	/* at this point, nothing can be received... */
+	i2400m_report_hook_flush(i2400m);
 }