On 12/5/18 7:07 AM, Oleksij Rempel wrote:
> Currently, (E)TP transfers will be aborted, as soon application will
> call close() or exit, as the socket will be automatically closed by the
> kernel.
With this patch, the application hangs on the close() call until all
data has been send out. This might take a while. What happens if you
attach a debugger? I think the wait_event_interruptible() will return as
attaching a debugger involves signals.
> Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> ---
> net/can/j1939/socket.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
> index d6332483350f..e003d3cae24c 100644
> --- a/net/can/j1939/socket.c
> +++ b/net/can/j1939/socket.c
> @@ -101,6 +101,13 @@ static inline void j1939_sock_pending_add(struct sock *sk)
> atomic_inc(&jsk->skb_pending);
> }
>
> +static int j1939_sock_pending_get(struct sock *sk)
> +{
> + struct j1939_sock *jsk = j1939_sk(sk);
> +
> + return atomic_read(&jsk->skb_pending);
> +}
> +
> void j1939_sock_pending_del(struct sock *sk)
> {
> struct j1939_sock *jsk = j1939_sk(sk);
> @@ -404,6 +411,9 @@ static int j1939_sk_release(struct socket *sock)
> if (jsk->state & J1939_SOCK_BOUND) {
> struct net_device *ndev;
>
> + wait_event_interruptible(jsk->waitq,
> + j1939_sock_pending_get(&jsk->sk) == 0);
If a signal is received, wait_event will return -ERESTARTSYS.
However EINTR is the currect return value close():
> EINTR The close() call was interrupted by a signal; see signal(7).
On Linux the filedescriptor is closed regardless of a signal or not:
> The EINTR error is a somewhat special case. Regarding the
> EINTR error, POSIX.1-2013 says:
>
> If close() is interrupted by a signal that is to be
> caught, it shall return -1 with errno set to EINTR and the state of
> fildes is unspecified.
>
> This permits the behavior that occurs on Linux and many other
> implementations, where, as with other errors that may be reported by
> close(), the file descriptor is guaranteed to be closed. However, it
> also permits another possibility: that the implementation returns an
> EINTR error and keeps the file descriptor open. (According to its
> documentation, HP-UX's close() does this.) The caller must then once
> more use close() to close the file descriptor, to avoid file
> descriptor leaks. This divergence in implementation behaviors
> provides a difficult hurdle for portable applications, since on
> many implementations, close() must not be called again after an EINTR
> error, and on at least one, close() must be called again. There are
> plans to address this conundrum for the next major release of the
> POSIX.1 standard.
So we have to check if the correct return value is received by the
close() call in userspace in case of a signal delivery.
> +
> spin_lock_bh(&j1939_socks_lock);
> list_del_init(&jsk->list);
> spin_unlock_bh(&j1939_socks_lock);
>
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
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