similar to: [PATCH] virtio: remove overzealous BUG_ON.

Currently, the virt_ring->enable_cb and virt_ring->disable_cb functions enforce that they were called only when callbacks were disabled and enabled respectively. However, in the current vring implementation, this isn't actually a bug. What's more, the virtio_net driver does not guard against double enabling or double disabling. All that needs to happen is for an rx notification to

Currently, the virt_ring->enable_cb and virt_ring->disable_cb functions enforce that they were called only when callbacks were disabled and enabled respectively. However, in the current vring implementation, this isn't actually a bug. What's more, the virtio_net driver does not guard against double enabling or double disabling. All that needs to happen is for an rx notification to

Hi Rusty, I hit a bug in virtio_ring.c:218 when I was stressing virtio_net using kvm with -smp 4. static void vring_disable_cb(struct virtqueue *_vq) { struct vring_virtqueue *vq = to_vvq(_vq); START_USE(vq); --> BUG_ON(vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT); vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;

Hi Rusty, I hit a bug in virtio_ring.c:218 when I was stressing virtio_net using kvm with -smp 4. static void vring_disable_cb(struct virtqueue *_vq) { struct vring_virtqueue *vq = to_vvq(_vq); START_USE(vq); --> BUG_ON(vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT); vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;

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

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:

This helper returns 1 if a call to add_buf will not fail with -ENOSPC. This will help callers that do while(1) { alloc() if (add_buf()) { free(); break; } } This will result in one less alloc/free exercise. Signed-off-by: Amit Shah <amit.shah at redhat.com> --- v2: return true/false instead of 1/0 drivers/virtio/virtio_ring.c | 8 ++++++++ include/linux/virtio.h |

This helper returns 1 if a call to add_buf will not fail with -ENOSPC. This will help callers that do while(1) { alloc() if (add_buf()) { free(); break; } } This will result in one less alloc/free exercise. Signed-off-by: Amit Shah <amit.shah at redhat.com> --- v2: return true/false instead of 1/0 drivers/virtio/virtio_ring.c | 8 ++++++++ include/linux/virtio.h |

The 'disable_cb' is really just a hint and as such, it's possible for more work to get queued up while callbacks are disabled. Under stress with an SMP guest, this printk triggers very frequently. There is no race here, this is how things are designed to work so let's just remove the printk. Signed-off-by: Anthony Liguori <aliguori at us.ibm.com> Acked-by: Rusty Russell

The 'disable_cb' is really just a hint and as such, it's possible for more work to get queued up while callbacks are disabled. Under stress with an SMP guest, this printk triggers very frequently. There is no race here, this is how things are designed to work so let's just remove the printk. Signed-off-by: Anthony Liguori <aliguori at us.ibm.com> Acked-by: Rusty Russell

This helper returns 1 if a call to add_buf will not fail with -ENOSPC. This will help callers that do while(1) { alloc() if (add_buf()) { free(); break; } } This will result in one less alloc/free exercise. Signed-off-by: Amit Shah <amit.shah at redhat.com> --- drivers/virtio/virtio_ring.c | 8 ++++++++ include/linux/virtio.h | 5 +++++ 2 files changed, 13

Rusty, Anthony, Dor, I need your brain power :-) On smp guests I have seen a problem with virtio (the version in curent Avi's git) which do not occur on single processor guests: kernel BUG at /space/kvm/drivers/virtio/virtio_ring.c:228! illegal operation: 0001 [#1] Modules linked in: ipv6 CPU: 2 Not tainted Process swapper (pid: 0, task: 000000000f83e038, ksp: 000000000f877d70) Krnl

Rusty, Anthony, Dor, I need your brain power :-) On smp guests I have seen a problem with virtio (the version in curent Avi's git) which do not occur on single processor guests: kernel BUG at /space/kvm/drivers/virtio/virtio_ring.c:228! illegal operation: 0001 [#1] Modules linked in: ipv6 CPU: 2 Not tainted Process swapper (pid: 0, task: 000000000f83e038, ksp: 000000000f877d70) Krnl

This helper returns 1 if a call to add_buf will not fail with -ENOSPC. This will help callers that do while(1) { alloc() if (add_buf()) { free(); break; } } This will result in one less alloc/free exercise. Signed-off-by: Amit Shah <amit.shah at redhat.com> --- drivers/virtio/virtio_ring.c | 8 ++++++++ include/linux/virtio.h | 5 +++++ 2 files changed, 13

I got the following oops during interface ifup. Unfortunately its not easily reproducable so I cant say for sure that my fix fixes this problem, but I am confident and I think its correct anyway: <2>kernel BUG at /space/kvm/drivers/virtio/virtio_ring.c:234! <4>illegal operation: 0001 [#1] PREEMPT SMP <4>Modules linked in: <4>CPU: 0 Not tainted

I got the following oops during interface ifup. Unfortunately its not easily reproducable so I cant say for sure that my fix fixes this problem, but I am confident and I think its correct anyway: <2>kernel BUG at /space/kvm/drivers/virtio/virtio_ring.c:234! <4>illegal operation: 0001 [#1] PREEMPT SMP <4>Modules linked in: <4>CPU: 0 Not tainted

Hi Dave, Nice driver optimization from Shirley, but requires a new virtio hook. Do you want to take both? I have nothing else overlapping it. Cheers, Rusty.

Hi Dave, Nice driver optimization from Shirley, but requires a new virtio hook. Do you want to take both? I have nothing else overlapping it. Cheers, Rusty.