netdev - [PATCH v2] xen/netback: Wake dealloc thread after completing zerocopy work

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <1438699259-28508-1-git-send-email-ross.lagerwall@citrix.com>
Date:	Tue, 4 Aug 2015 15:40:59 +0100
From:	Ross Lagerwall <ross.lagerwall@...rix.com>
To:	<netdev@...r.kernel.org>
CC:	<xen-devel@...ts.xenproject.org>, Wei Liu <wei.liu2@...rix.com>,
	"Ian Campbell" <ian.campbell@...rix.com>,
	Ross Lagerwall <ross.lagerwall@...rix.com>
Subject: [PATCH v2] xen/netback: Wake dealloc thread after completing zerocopy work

Waking the dealloc thread before decrementing inflight_packets is racy
because it means the thread may go to sleep before inflight_packets is
decremented. If kthread_stop() has already been called, the dealloc
thread may wait forever with nothing to wake it. Instead, wake the
thread only after decrementing inflight_packets.

Signed-off-by: Ross Lagerwall <ross.lagerwall@...rix.com>
---
Changed in V2: Move wakeup into zerocopy_complete function.

 drivers/net/xen-netback/interface.c | 6 ++++++
 drivers/net/xen-netback/netback.c   | 1 -
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 1a83e19..28577a3 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -61,6 +61,12 @@ void xenvif_skb_zerocopy_prepare(struct xenvif_queue *queue,
 void xenvif_skb_zerocopy_complete(struct xenvif_queue *queue)
 {
 	atomic_dec(&queue->inflight_packets);
+
+	/* Wake the dealloc thread _after_ decrementing inflight_packets so
+	 * that if kthread_stop() has already been called, the dealloc thread
+	 * does not wait forever with nothing to wake it.
+	 */
+	wake_up(&queue->dealloc_wq);
 }
 
 int xenvif_schedulable(struct xenvif *vif)
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 7d50711..09ffda4 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1536,7 +1536,6 @@ void xenvif_zerocopy_callback(struct ubuf_info *ubuf, bool zerocopy_success)
 		smp_wmb();
 		queue->dealloc_prod++;
 	} while (ubuf);
-	wake_up(&queue->dealloc_wq);
 	spin_unlock_irqrestore(&queue->callback_lock, flags);
 
 	if (likely(zerocopy_success))
-- 
2.1.0

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html