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Message-ID: <20190521055650-mutt-send-email-mst@kernel.org> Date: Tue, 21 May 2019 06:05:31 -0400 From: "Michael S. Tsirkin" <mst@...hat.com> To: Stefano Garzarella <sgarzare@...hat.com> Cc: Jason Wang <jasowang@...hat.com>, netdev@...r.kernel.org, Stefan Hajnoczi <stefanha@...hat.com> Subject: Re: Question about IRQs during the .remove() of virtio-vsock driver On Tue, May 21, 2019 at 11:44:07AM +0200, Stefano Garzarella wrote: > Hi Micheal, Jason, > as suggested by Stefan, I'm checking if we have some races in the > virtio-vsock driver. We found some races in the .probe() and .remove() > with the upper layer (socket) and I'll fix it. > > Now my attention is on the bottom layer (virtio device) and my question is: > during the .remove() of virtio-vsock driver (virtio_vsock_remove), could happen > that an IRQ comes and one of our callback (e.g. virtio_vsock_rx_done()) is > executed, queueing new works? > > I tried to follow the code in both cases (device unplugged or module removed) > and maybe it couldn't happen because we remove it from bus's knowledge, > but I'm not sure and your advice would be very helpful. > > Thanks in advance, > Stefano Great question! This should be better documented: patches welcome! Here's my understanding: A typical removal flow works like this: - prevent linux from sending new kick requests to device and flush such outstanding requests if any (device can still send notifications to linux) - call vi->vdev->config->reset(vi->vdev); this will flush all device writes and interrupts. device will not use any more buffers. previously outstanding callbacks might still be active. - Then call vdev->config->del_vqs(vdev); to flush outstanding callbacks if any. -- MST
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