On 07/20/2012 07:41 PM, Sage Weil wrote:
> Hold the mutex while twiddling all of the state bits to avoid possible
> races. While we're here, make not of why we cannot close the socket
> directly.
>
> Signed-off-by: Sage Weil <sage@xxxxxxxxxxx>
Looks OK to me. A quick scan seems to show that the
state and flag bits are *almost* always set while the
mutex is held. The one counterexample I found was for
the STANDBY state bit in clear_standby() (but I really
didn't look very closely).
Anyway, I think this looks fine--it makes things safer
even if there could be another imperfection somewhere.
Reviewed-by: Alex Elder <elder@xxxxxxxxxxx>
> ---
> net/ceph/messenger.c | 8 +++++++-
> 1 files changed, 7 insertions(+), 1 deletions(-)
>
> diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
> index 7105908..e24310e 100644
> --- a/net/ceph/messenger.c
> +++ b/net/ceph/messenger.c
> @@ -503,6 +503,7 @@ static void reset_connection(struct ceph_connection *con)
> */
> void ceph_con_close(struct ceph_connection *con)
> {
> + mutex_lock(&con->mutex);
> dout("con_close %p peer %s\n", con,
> ceph_pr_addr(&con->peer_addr.in_addr));
> clear_bit(NEGOTIATING, &con->state);
> @@ -515,11 +516,16 @@ void ceph_con_close(struct ceph_connection *con)
> clear_bit(KEEPALIVE_PENDING, &con->flags);
> clear_bit(WRITE_PENDING, &con->flags);
>
> - mutex_lock(&con->mutex);
> reset_connection(con);
> con->peer_global_seq = 0;
> cancel_delayed_work(&con->work);
> mutex_unlock(&con->mutex);
> +
> + /*
> + * We cannot close the socket directly from here because the
> + * work threads use it without holding the mutex. Instead, let
> + * con_work() do it.
> + */
> queue_con(con);
> }
> EXPORT_SYMBOL(ceph_con_close);
>
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