similar to: [PATCH] virtio_net: remove overzealous printk

Herbert tells me that returning NETDEV_TX_BUSY from hard_start_xmit is seen as a poor thing to do; we should cache the packet and stop the queue. Signed-off-by: Rusty Russell <rusty at rustcorp.com.au> --- drivers/net/virtio_net.c | 57 +++++++++++++++++++++++++++++++---------------- 1 file changed, 38 insertions(+), 19 deletions(-) diff -r a936d320f6d5 drivers/net/virtio_net.c ---

Herbert tells me that returning NETDEV_TX_BUSY from hard_start_xmit is seen as a poor thing to do; we should cache the packet and stop the queue. Signed-off-by: Rusty Russell <rusty at rustcorp.com.au> --- drivers/net/virtio_net.c | 57 +++++++++++++++++++++++++++++++---------------- 1 file changed, 38 insertions(+), 19 deletions(-) diff -r a936d320f6d5 drivers/net/virtio_net.c ---

There is a race in virtio_net, dealing with disabling/enabling the callback. I saw the following oops: kernel BUG at /space/kvm/drivers/virtio/virtio_ring.c:218! illegal operation: 0001 [#1] SMP Modules linked in: sunrpc dm_mod CPU: 2 Not tainted 2.6.25-rc1zlive-host-10623-gd358142-dirty #99 Process swapper (pid: 0, task: 000000000f85a610, ksp: 000000000f873c60) Krnl PSW : 0404300180000000

There is a race in virtio_net, dealing with disabling/enabling the callback. I saw the following oops: kernel BUG at /space/kvm/drivers/virtio/virtio_ring.c:218! illegal operation: 0001 [#1] SMP Modules linked in: sunrpc dm_mod CPU: 2 Not tainted 2.6.25-rc1zlive-host-10623-gd358142-dirty #99 Process swapper (pid: 0, task: 000000000f85a610, ksp: 000000000f873c60) Krnl PSW : 0404300180000000

Herbert tells me that returning NETDEV_TX_BUSY from hard_start_xmit is seen as a poor thing to do; we should cache the packet and stop the queue. Signed-off-by: Rusty Russell <rusty at rustcorp.com.au> --- drivers/net/virtio_net.c | 58 ++++++++++++++++++++++++++++++++--------------- 1 file changed, 40 insertions(+), 18 deletions(-) diff -r 26ba2dd67f46 drivers/net/virtio_net.c ---

Herbert tells me that returning NETDEV_TX_BUSY from hard_start_xmit is seen as a poor thing to do; we should cache the packet and stop the queue. Signed-off-by: Rusty Russell <rusty at rustcorp.com.au> --- drivers/net/virtio_net.c | 58 ++++++++++++++++++++++++++++++++--------------- 1 file changed, 40 insertions(+), 18 deletions(-) diff -r 26ba2dd67f46 drivers/net/virtio_net.c ---

Hello Rusty, seems that we still have a problem with virtio_net and the enable_cb callback. During a long running network stress tests with virtio and got the following oops: ------------[ cut here ]------------ kernel BUG at drivers/virtio/virtio_ring.c:230! illegal operation: 0001 [#1] SMP Modules linked in: CPU: 0 Not tainted 2.6.26-rc2-kvm-00436-gc94c08b-dirty #34 Process netserver (pid:

Hello Rusty, seems that we still have a problem with virtio_net and the enable_cb callback. During a long running network stress tests with virtio and got the following oops: ------------[ cut here ]------------ kernel BUG at drivers/virtio/virtio_ring.c:230! illegal operation: 0001 [#1] SMP Modules linked in: CPU: 0 Not tainted 2.6.26-rc2-kvm-00436-gc94c08b-dirty #34 Process netserver (pid:

The 'disable_cb' callback is designed as an optimization to tell the host we don't need callbacks now. As it is not reliable, the debug check is overzealous: it can happen on two CPUs at the same time. Document this. Even if it were reliable, the virtio_net driver doesn't disable callbacks on transmit so the START_USE/END_USE debugging reentrance protection can be easily tripped

The 'disable_cb' callback is designed as an optimization to tell the host we don't need callbacks now. As it is not reliable, the debug check is overzealous: it can happen on two CPUs at the same time. Document this. Even if it were reliable, the virtio_net driver doesn't disable callbacks on transmit so the START_USE/END_USE debugging reentrance protection can be easily tripped

Signed-off-by: Dor Laor <dor.laor at qumranet.com> --- hack-module.awk | 28 +++++++++++++++++++++++++++- 1 files changed, 27 insertions(+), 1 deletions(-) diff --git a/hack-module.awk b/hack-module.awk index 580090b..bd63fb9 100644 --- a/hack-module.awk +++ b/hack-module.awk @@ -45,8 +45,8 @@ print " return 1;"; print " }"; print ""; -

Rusty, the patch "virtio: imply disable_cb on callbacks" is on your tree. I'd like to figure out how it works: for example: diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -69,6 +69,8 @@ static void blk_done(struct virtqueue *v /* In case queue is stopped waiting for more buffers. */

Rusty, the patch "virtio: imply disable_cb on callbacks" is on your tree. I'd like to figure out how it works: for example: diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -69,6 +69,8 @@ static void blk_done(struct virtqueue *v /* In case queue is stopped waiting for more buffers. */

Since we want to reset the device to remove them, this is simpler (device is reset for us on driver remove). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> --- drivers/net/virtio_net.c | 44 +++++++++++++++++++++++++------------------- 1 file changed, 25 insertions(+), 19 deletions(-) diff -r 7e5b3ff06f60 drivers/net/virtio_net.c --- a/drivers/net/virtio_net.c Wed Jan 23 22:53:14

Since we want to reset the device to remove them, this is simpler (device is reset for us on driver remove). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> --- drivers/net/virtio_net.c | 44 +++++++++++++++++++++++++------------------- 1 file changed, 25 insertions(+), 19 deletions(-) diff -r 7e5b3ff06f60 drivers/net/virtio_net.c --- a/drivers/net/virtio_net.c Wed Jan 23 22:53:14

virtqueue ops were introduced in the hope that we'll have multiple implementations besides virtio_ring, but none have surfaced so far, and given that existing virtio ring is deployed in production we are likely stuck with it now, so this layer just adds complexity and overhead. Further, the need to pass vq twice to each call (as in dev->vq->vq_ops->kick(dev->vq) ) adds potential

virtqueue ops were introduced in the hope that we'll have multiple implementations besides virtio_ring, but none have surfaced so far, and given that existing virtio ring is deployed in production we are likely stuck with it now, so this layer just adds complexity and overhead. Further, the need to pass vq twice to each call (as in dev->vq->vq_ops->kick(dev->vq) ) adds potential

This effectively reverts 99ffc696d10b28580fe93441d627cf290ac4484c "virtio: wean net driver off NETDEV_TX_BUSY". The complexity of queuing an skb (setting a tasklet to re-xmit) is questionable, especially once we get rid of the other reason for the tasklet in the next patch. If the skb won't fit in the tx queue, just return NETDEV_TX_BUSY. It might be frowned upon, but it's

This effectively reverts 99ffc696d10b28580fe93441d627cf290ac4484c "virtio: wean net driver off NETDEV_TX_BUSY". The complexity of queuing an skb (setting a tasklet to re-xmit) is questionable, especially once we get rid of the other reason for the tasklet in the next patch. If the skb won't fit in the tx queue, just return NETDEV_TX_BUSY. It might be frowned upon, but it's

If we fail to transmit a packet, we assume the queue is full and put the skb into last_xmit_skb. However, if more space frees up before we xmit it, we loop, and the result can be transmitting the same skb twice. Fix is simple: set skb to NULL if we've used it in some way, and check before sending. Signed-off-by: Rusty Russell <rusty at rustcorp.com.au> --- drivers/net/virtio_net.c |