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    SubjectRe: [PATCH v1 11/13] xen/pvcalls: implement release command
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    On 22/07/17 02:12, Stefano Stabellini wrote:
    > Send PVCALLS_RELEASE to the backend and wait for a reply. Take both
    > in_mutex and out_mutex to avoid concurrent accesses. Then, free the
    > socket.
    >
    > Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
    > CC: boris.ostrovsky@oracle.com
    > CC: jgross@suse.com
    > ---
    > drivers/xen/pvcalls-front.c | 86 +++++++++++++++++++++++++++++++++++++++++++++
    > drivers/xen/pvcalls-front.h | 1 +
    > 2 files changed, 87 insertions(+)
    >
    > diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
    > index b6cfb7d..bd3dfac 100644
    > --- a/drivers/xen/pvcalls-front.c
    > +++ b/drivers/xen/pvcalls-front.c
    > @@ -174,6 +174,24 @@ static irqreturn_t pvcalls_front_conn_handler(int irq, void *sock_map)
    > return IRQ_HANDLED;
    > }
    >
    > +static void pvcalls_front_free_map(struct pvcalls_bedata *bedata,
    > + struct sock_mapping *map)
    > +{
    > + int i;
    > +
    > + spin_lock(&bedata->pvcallss_lock);
    > + if (!list_empty(&map->list))
    > + list_del_init(&map->list);
    > + spin_unlock(&bedata->pvcallss_lock);
    > +
    > + /* what if the thread waiting still need access? */

    Is this handled? If not, why is it no problem?

    > + for (i = 0; i < (1 << map->active.ring->ring_order); i++)
    > + gnttab_end_foreign_access(map->active.ring->ref[i], 0, 0);
    > + gnttab_end_foreign_access(map->active.ref, 0, 0);
    > + free_page((unsigned long)map->active.ring);
    > + unbind_from_irqhandler(map->active.irq, map);
    > +}
    > +
    > int pvcalls_front_socket(struct socket *sock)
    > {
    > struct pvcalls_bedata *bedata;
    > @@ -805,6 +823,74 @@ unsigned int pvcalls_front_poll(struct file *file, struct socket *sock,
    > return pvcalls_front_poll_passive(file, bedata, map, wait);
    > }
    >
    > +int pvcalls_front_release(struct socket *sock)
    > +{
    > + struct pvcalls_bedata *bedata;
    > + struct sock_mapping *map;
    > + int req_id, notify;
    > + struct xen_pvcalls_request *req;
    > +
    > + if (!pvcalls_front_dev)
    > + return -EIO;
    > + bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
    > + if (!bedata)
    > + return -EIO;
    > +
    > + if (sock->sk == NULL)
    > + return 0;
    > +
    > + map = (struct sock_mapping *) READ_ONCE(sock->sk->sk_send_head);
    > + if (map == NULL)
    > + return 0;
    > + WRITE_ONCE(sock->sk->sk_send_head, NULL);
    > +
    > + spin_lock(&bedata->pvcallss_lock);
    > + req_id = bedata->ring.req_prod_pvt & (RING_SIZE(&bedata->ring) - 1);
    > + BUG_ON(req_id >= PVCALLS_NR_REQ_PER_RING);
    > + if (RING_FULL(&bedata->ring) ||
    > + READ_ONCE(bedata->rsp[req_id].req_id) != PVCALLS_INVALID_ID) {
    > + spin_unlock(&bedata->pvcallss_lock);
    > + return -EAGAIN;

    Isn't it a problem you already cleared sock->sk->sk_send_head?


    Juergen

    > + }
    > + req = RING_GET_REQUEST(&bedata->ring, req_id);
    > + req->req_id = req_id;
    > + req->cmd = PVCALLS_RELEASE;
    > + req->u.release.id = (uint64_t)sock;
    > +
    > + bedata->ring.req_prod_pvt++;
    > + RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
    > + spin_unlock(&bedata->pvcallss_lock);
    > + if (notify)
    > + notify_remote_via_irq(bedata->irq);
    > +
    > + wait_event(bedata->inflight_req,
    > + READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
    > +
    > + if (map->active_socket) {
    > + /*
    > + * Set in_error and wake up inflight_conn_req to force
    > + * recvmsg waiters to exit.
    > + */
    > + map->active.ring->in_error = -EBADF;
    > + wake_up_interruptible(&map->active.inflight_conn_req);
    > +
    > + mutex_lock(&map->active.in_mutex);
    > + mutex_lock(&map->active.out_mutex);
    > + pvcalls_front_free_map(bedata, map);
    > + mutex_unlock(&map->active.out_mutex);
    > + mutex_unlock(&map->active.in_mutex);
    > + kfree(map);
    > + } else {
    > + spin_lock(&bedata->pvcallss_lock);
    > + list_del_init(&map->list);
    > + kfree(map);
    > + spin_unlock(&bedata->pvcallss_lock);
    > + }
    > + WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID);
    > +
    > + return 0;
    > +}
    > +
    > static const struct xenbus_device_id pvcalls_front_ids[] = {
    > { "pvcalls" },
    > { "" }
    > diff --git a/drivers/xen/pvcalls-front.h b/drivers/xen/pvcalls-front.h
    > index 25e05b8..3332978 100644
    > --- a/drivers/xen/pvcalls-front.h
    > +++ b/drivers/xen/pvcalls-front.h
    > @@ -23,5 +23,6 @@ int pvcalls_front_recvmsg(struct socket *sock,
    > unsigned int pvcalls_front_poll(struct file *file,
    > struct socket *sock,
    > poll_table *wait);
    > +int pvcalls_front_release(struct socket *sock);
    >
    > #endif
    >

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