Re: [Xen-devel] [PATCH 03/11] mini-os/xenbus: Add missing locks to xb_write

[Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>]

Ian Jackson, le Fri 20 Jun 2014 20:04:42 +0100, a écrit :
> xb_write was missing any locking against concurrent calls.

Well, yes, in its current form mini-os was not really meant to run with
multiple processors. There are probably quite other issues like that in
there.

> Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>

Acked-by: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>

> ---
>  xen/xenbus/xenbus.c |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/xen/xenbus/xenbus.c b/xen/xenbus/xenbus.c
> index 0958604..a06dc30 100644
> --- a/xen/xenbus/xenbus.c
> +++ b/xen/xenbus/xenbus.c
> @@ -45,6 +45,7 @@
>  
>  static struct xenstore_domain_interface *xenstore_buf;
>  static DECLARE_WAIT_QUEUE_HEAD(xb_waitq);
> +static spinlock_t xb_lock = SPIN_LOCK_UNLOCKED; /* protects xenbus req ring 
> */
>  DECLARE_WAIT_QUEUE_HEAD(xenbus_watch_queue);
>  
>  xenbus_event_queue xenbus_events;
> @@ -372,6 +373,8 @@ static void xb_write(int type, int req_id, 
> xenbus_transaction_t trans_id,
>      cur_req = &header_req;
>  
>      BUG_ON(len > XENSTORE_RING_SIZE);
> +
> +    spin_lock(&xb_lock);
>      /* Wait for the ring to drain to the point where we can send the
>         message. */
>      prod = xenstore_buf->req_prod;
> @@ -380,9 +383,11 @@ static void xb_write(int type, int req_id, 
> xenbus_transaction_t trans_id,
>          /* Wait for there to be space on the ring */
>          DEBUG("prod %d, len %d, cons %d, size %d; waiting.\n",
>                  prod, len, xenstore_buf->req_cons, XENSTORE_RING_SIZE);
> +        spin_unlock(&xb_lock);
>          wait_event(xb_waitq,
>                  xenstore_buf->req_prod + len - xenstore_buf->req_cons <=
>                  XENSTORE_RING_SIZE);
> +        spin_lock(&xb_lock);
>          DEBUG("Back from wait.\n");
>          prod = xenstore_buf->req_prod;
>      }
> @@ -419,6 +424,7 @@ static void xb_write(int type, int req_id, 
> xenbus_transaction_t trans_id,
>      wmb();
>  
>      xenstore_buf->req_prod += len;
> +    spin_unlock(&xb_lock);
>  
>      /* Send evtchn to notify remote */
>      notify_remote_via_evtchn(start_info.store_evtchn);
> -- 
> 1.7.10.4
> 
> 
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> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel
> 

-- 
Samuel
<N>  sl  -  display animations aimed to correct users who accidentally enter
<N>        sl instead of ls.

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