From patchwork Tue Aug 4 14:40:59 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ross Lagerwall X-Patchwork-Id: 503636 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 875541401B5 for ; Wed, 5 Aug 2015 00:56:47 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934189AbbHDOl4 (ORCPT ); Tue, 4 Aug 2015 10:41:56 -0400 Received: from smtp.citrix.com ([66.165.176.89]:10413 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934125AbbHDOlz (ORCPT ); Tue, 4 Aug 2015 10:41:55 -0400 X-IronPort-AV: E=Sophos;i="5.15,609,1432598400"; d="scan'208";a="287842699" From: Ross Lagerwall To: CC: , Wei Liu , "Ian Campbell" , Ross Lagerwall Subject: [PATCH v2] xen/netback: Wake dealloc thread after completing zerocopy work Date: Tue, 4 Aug 2015 15:40:59 +0100 Message-ID: <1438699259-28508-1-git-send-email-ross.lagerwall@citrix.com> X-Mailer: git-send-email 2.1.0 MIME-Version: 1.0 X-DLP: MIA1 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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 --- 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))