Re: [PATCH] xen/pvcalls: don't call bind_evtchn_to_irqhandler() under lock

[Juergen Gross]

On 28.03.23 12:34, Oleksandr Tyshchenko wrote:
> On 28.03.23 12:39, Juergen Gross wrote:
>
> Hello Juergen
>
>
> > bind_evtchn_to_irqhandler() shouldn't be called under spinlock, as it
> > can sleep.
> >
> > This requires to move the calls of create_active() out of the locked
> > regions. This is no problem, as the worst which could happen would be
> > a spurious call of the interrupt handler, causing a spurious wake_up().
> >
> > Reported-by: Dan Carpenter <error27@xxxxxxxxx>
> > Link: https://lore.kernel.org/lkml/Y+JUIl64UDmdkboh@kadam/
> > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> > ---
> >   drivers/xen/pvcalls-front.c | 46 ++++++++++++++++++++++---------------
> >   1 file changed, 27 insertions(+), 19 deletions(-)
> >
> > diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
> > index d5d589bda243..6e5d712e3115 100644
> > --- a/drivers/xen/pvcalls-front.c
> > +++ b/drivers/xen/pvcalls-front.c
> > @@ -227,22 +227,31 @@ static irqreturn_t pvcalls_front_event_handler(int irq, 
> > void *dev_id)
> >   static void free_active_ring(struct sock_mapping *map);
> > -static void pvcalls_front_free_map(struct pvcalls_bedata *bedata,
> > -                   struct sock_mapping *map)
> > +static void pvcalls_front_destroy_active(struct pvcalls_bedata *bedata,
> > +                     struct sock_mapping *map)
> >   {
> >       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);
> > +    if (bedata) {
> > +        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], NULL);
> >       gnttab_end_foreign_access(map->active.ref, NULL);
> > +
> >       free_active_ring(map);
> > +}
> > +
> > +static void pvcalls_front_free_map(struct pvcalls_bedata *bedata,
> > +                   struct sock_mapping *map)
> > +{
> > +    pvcalls_front_destroy_active(bedata, map);
> >       kfree(map);
> >   }
> > @@ -433,19 +442,18 @@ int pvcalls_front_connect(struct socket *sock, struct 
> > sockaddr *addr,
> >           pvcalls_exit_sock(sock);
> >           return ret;
> >       }
> > -
> > -    spin_lock(&bedata->socket_lock);
> > -    ret = get_request(bedata, &req_id);
> > +    ret = create_active(map, &evtchn);
> >       if (ret < 0) {
> > -        spin_unlock(&bedata->socket_lock);
> >           free_active_ring(map);
> >           pvcalls_exit_sock(sock);
> >           return ret;
> >       }
> > -    ret = create_active(map, &evtchn);
> > +
> > +    spin_lock(&bedata->socket_lock);
> > +    ret = get_request(bedata, &req_id);
> >       if (ret < 0) {
> >           spin_unlock(&bedata->socket_lock);
> > -        free_active_ring(map);
> > +        pvcalls_front_destroy_active(NULL, map);
> >           pvcalls_exit_sock(sock);
> >           return ret;
> >       }
> > @@ -821,28 +829,28 @@ int pvcalls_front_accept(struct socket *sock, struct 
> > socket *newsock, int flags)
> >           pvcalls_exit_sock(sock);
> >           return ret;
> >       }
> > -    spin_lock(&bedata->socket_lock);
> > -    ret = get_request(bedata, &req_id);
> > +    ret = create_active(map2, &evtchn);
> >       if (ret < 0) {
> > +        free_active_ring(map2);
> > +        kfree(map2);
> >           clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
> >                 (void *)&map->passive.flags);
> >           spin_unlock(&bedata->socket_lock);
>
>
> Looks like we also need to remove spin_unlock() above, correct?

Thanks for catching!


Juergen

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