From: John Fastabend <john.fastabend@gmail.com>
To: bpf@vger.kernel.org
Cc: bjorn.topel@intel.com, songliubraving@fb.com,
john.fastabend@gmail.com, ast@kernel.org, daniel@iogearbox.net,
toke@redhat.com, maciej.fijalkowski@intel.com,
netdev@vger.kernel.org
Subject: [PATCH bpf-next v2 2/3] bpf: xdp, virtio_net use access ptr macro for xdp enable check
Date: Sat, 25 Jan 2020 19:58:52 -0800 [thread overview]
Message-ID: <1580011133-17784-3-git-send-email-john.fastabend@gmail.com> (raw)
In-Reply-To: <1580011133-17784-1-git-send-email-john.fastabend@gmail.com>
virtio_net currently relies on rcu critical section to access the xdp
program in its xdp_xmit handler. However, the pointer to the xdp program
is only used to do a NULL pointer comparison to determine if xdp is
enabled or not.
Use rcu_access_pointer() instead of rcu_dereference() to reflect this.
Then later when we drop rcu_read critical section virtio_net will not
need in special handling.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
---
drivers/net/virtio_net.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 4d7d5434..945eabc 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -501,7 +501,7 @@ static int virtnet_xdp_xmit(struct net_device *dev,
/* Only allow ndo_xdp_xmit if XDP is loaded on dev, as this
* indicate XDP resources have been successfully allocated.
*/
- xdp_prog = rcu_dereference(rq->xdp_prog);
+ xdp_prog = rcu_access_pointer(rq->xdp_prog);
if (!xdp_prog)
return -ENXIO;
--
2.7.4
next prev parent reply other threads:[~2020-01-26 3:59 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-26 3:58 [PATCH bpf-next v2 0/3] XDP flush cleanups John Fastabend
2020-01-26 3:58 ` [PATCH bpf-next v2 1/3] bpf: xdp, update devmap comments to reflect napi/rcu usage John Fastabend
2020-01-26 21:28 ` Jesper Dangaard Brouer
2020-01-26 3:58 ` John Fastabend [this message]
2020-01-26 21:28 ` [PATCH bpf-next v2 2/3] bpf: xdp, virtio_net use access ptr macro for xdp enable check Jesper Dangaard Brouer
2020-01-26 3:58 ` [PATCH bpf-next v2 3/3] bpf: xdp, remove no longer required rcu_read_{un}lock() John Fastabend
2020-01-26 21:30 ` Jesper Dangaard Brouer
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