lkml.org 
[lkml]   [2017]   [Sep]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v4 12/13] xen/pvcalls: implement release command
From
Date

>
> +static void pvcalls_front_free_map(struct pvcalls_bedata *bedata,
> + struct sock_mapping *map)

I just noticed: pvcalls_front_free_map() is referenced by patches 2 and 8.

> +{
> + int i;
> +
> + unbind_from_irqhandler(map->active.irq, map);
> +
> + spin_lock(&bedata->socket_lock);
> + if (!list_empty(&map->list))
> + list_del_init(&map->list);
> + spin_unlock(&bedata->socket_lock);
> +
> + for (i = 0; i < (1 << PVCALLS_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);
> +}
> +
> int pvcalls_front_socket(struct socket *sock)
> {
> struct pvcalls_bedata *bedata;
> @@ -960,6 +978,92 @@ unsigned int pvcalls_front_poll(struct file *file, struct socket *sock,
> return ret;
> }
>
> +int pvcalls_front_release(struct socket *sock)
> +{
> + struct pvcalls_bedata *bedata;
> + struct sock_mapping *map;
> + int req_id, notify, ret;
> + struct xen_pvcalls_request *req;
> +
> + pvcalls_enter;
> + if (!pvcalls_front_dev) {
> + pvcalls_exit;
> + return -EIO;
> + }
> + if (sock->sk == NULL) {
> + pvcalls_exit;
> + return 0;
> + }
> +
> + bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
> +
> + map = (struct sock_mapping *) sock->sk->sk_send_head;
> + if (map == NULL) {
> + pvcalls_exit;
> + return 0;
> + }
> +
> + spin_lock(&bedata->socket_lock);
> + ret = get_request(bedata, &req_id);
> + if (ret < 0) {
> + spin_unlock(&bedata->socket_lock);
> + pvcalls_exit;
> + return ret;
> + }
> + sock->sk->sk_send_head = NULL;
> +
> + req = RING_GET_REQUEST(&bedata->ring, req_id);
> + req->req_id = req_id;
> + req->cmd = PVCALLS_RELEASE;
> + req->u.release.id = (uint64_t)map;
> +
> + bedata->ring.req_prod_pvt++;
> + RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
> + spin_unlock(&bedata->socket_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);
> +
> + /*
> + * Wait until there are no more waiters on the mutexes.
> + * We know that no new waiters can be added because sk_send_head
> + * is set to NULL -- we only need to wait for the existing
> + * waiters to return.
> + */
> + while (!mutex_trylock(&map->active.in_mutex) ||
> + !mutex_trylock(&map->active.out_mutex))
> + cpu_relax();


What if you manage to grab the locks before waiters get to run? for
example, in recvmsg:

while (!(flags & MSG_DONTWAIT) && !pvcalls_front_read_todo(map)) {
wait_event_interruptible(map->active.inflight_conn_req,
pvcalls_front_read_todo(map));
}
ret = __read_ring(map->active.ring, &map->active.data,
&msg->msg_iter, len, flags);

map will be freed (by pvcalls_front_free_map() below) before __read_ring
is passed the just-freed ring.


> +
> + pvcalls_front_free_map(bedata, map);
> + kfree(map);


-boris


\
 
 \ /
  Last update: 2017-09-23 00:44    [W:0.261 / U:1.452 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site