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From:   Jason Wang <jasowang@redhat.com>
To:     mst@redhat.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com,
        davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
        pabeni@redhat.com
Cc:     virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, alvaro.karsz@solid-run.com
Subject: [PATCH V3 net-next 2/2] virtio-net: add cond_resched() to the command waiting loop
Date:   Wed, 24 May 2023 16:18:42 +0800
Message-Id: <20230524081842.3060-3-jasowang@redhat.com>
In-Reply-To: <20230524081842.3060-1-jasowang@redhat.com>
References: <20230524081842.3060-1-jasowang@redhat.com>
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Adding cond_resched() to the command waiting loop for a better
co-operation with the scheduler. This allows to give CPU a breath to
run other task(workqueue) instead of busy looping when preemption is
not allowed on a device whose CVQ might be slow.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/net/virtio_net.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 5d2f1da4eaa0..de498dbbf0d4 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2207,8 +2207,10 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
 	 * into the hypervisor, so the request should be handled immediately.
 	 */
 	while (!virtqueue_get_buf(vi->cvq, &tmp) &&
-	       !virtqueue_is_broken(vi->cvq))
+	       !virtqueue_is_broken(vi->cvq)) {
+		cond_resched();
 		cpu_relax();
+	}
 
 	return vi->ctrl->status == VIRTIO_NET_OK;
 }
-- 
2.25.1