linux-kernel - [PATCH 3.16 123/148] macvlan: schedule bc

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Message-ID: <lsq.1581185941.238945398@decadent.org.uk>
Date:   Sat, 08 Feb 2020 18:21:02 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Menglong Dong" <dong.menglong@....com.cn>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.16 123/148] macvlan: schedule bc_work even if error

3.16.82-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Menglong Dong <dong.menglong@....com.cn>

commit 1d7ea55668878bb350979c377fc72509dd6f5b21 upstream.

While enqueueing a broadcast skb to port->bc_queue, schedule_work()
is called to add port->bc_work, which processes the skbs in
bc_queue, to "events" work queue. If port->bc_queue is full, the
skb will be discarded and schedule_work(&port->bc_work) won't be
called. However, if port->bc_queue is full and port->bc_work is not
running or pending, port->bc_queue will keep full and schedule_work()
won't be called any more, and all broadcast skbs to macvlan will be
discarded. This case can happen:

macvlan_process_broadcast() is the pending function of port->bc_work,
it moves all the skbs in port->bc_queue to the queue "list", and
processes the skbs in "list". During this, new skbs will keep being
added to port->bc_queue in macvlan_broadcast_enqueue(), and
port->bc_queue may already full when macvlan_process_broadcast()
return. This may happen, especially when there are a lot of real-time
threads and the process is preempted.

Fix this by calling schedule_work(&port->bc_work) even if
port->bc_work is full in macvlan_broadcast_enqueue().

Fixes: 412ca1550cbe ("macvlan: Move broadcasts into a work queue")
Signed-off-by: Menglong Dong <dong.menglong@....com.cn>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/net/macvlan.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -262,10 +262,11 @@ static void macvlan_broadcast_enqueue(st
 	}
 	spin_unlock(&port->bc_queue.lock);

+	schedule_work(&port->bc_work);
+
 	if (err)
 		goto free_nskb;

-	schedule_work(&port->bc_work);
 	return;

 free_nskb: