On Tue, 20 Sep 2011 17:49:27 +0400
Stanislav Kinsbursky <skinsbursky@xxxxxxxxxxxxx> wrote:
> v5: fixed races with rpcb_users in rpcb_get_local()
>
> This helpers will be used for dynamical creation and destruction of rpcbind
> clients.
> Variable rpcb_users is actually a counter of lauched RPC services. If rpcbind
> clients has been created already, then we just increase rpcb_users.
>
> Signed-off-by: Stanislav Kinsbursky <skinsbursky@xxxxxxxxxxxxx>
>
> ---
> net/sunrpc/rpcb_clnt.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 53 insertions(+), 0 deletions(-)
>
> diff --git a/net/sunrpc/rpcb_clnt.c b/net/sunrpc/rpcb_clnt.c
> index e45d2fb..5f4a406 100644
> --- a/net/sunrpc/rpcb_clnt.c
> +++ b/net/sunrpc/rpcb_clnt.c
> @@ -114,6 +114,9 @@ static struct rpc_program rpcb_program;
> static struct rpc_clnt * rpcb_local_clnt;
> static struct rpc_clnt * rpcb_local_clnt4;
> +DEFINE_SPINLOCK(rpcb_clnt_lock);
> +unsigned int rpcb_users;
> +
> struct rpcbind_args {
> struct rpc_xprt * r_xprt;
> @@ -161,6 +164,56 @@ static void rpcb_map_release(void *data)
> kfree(map);
> }
> +static int rpcb_get_local(void)
> +{
> + int cnt;
> +
> + spin_lock(&rpcb_clnt_lock);
> + if (rpcb_users)
> + rpcb_users++;
> + cnt = rpcb_users;
> + spin_unlock(&rpcb_clnt_lock);
> +
> + return cnt;
> +}
> +
> +void rpcb_put_local(void)
> +{
> + struct rpc_clnt *clnt = rpcb_local_clnt;
> + struct rpc_clnt *clnt4 = rpcb_local_clnt4;
> + int shutdown;
> +
> + spin_lock(&rpcb_clnt_lock);
> + if (--rpcb_users == 0) {
> + rpcb_local_clnt = NULL;
> + rpcb_local_clnt4 = NULL;
> + }
In the function below, you mention that the above pointers are
protected by rpcb_create_local_mutex, but it looks like they get reset
here without that being held?
Might it be simpler to just protect rpcb_users with the
rpcb_create_local_mutex and ensure that it's held whenever you call one
of these routines? None of these are codepaths are particularly hot.
> + shutdown = !rpcb_users;
> + spin_unlock(&rpcb_clnt_lock);
> +
> + if (shutdown) {
> + /*
> + * cleanup_rpcb_clnt - remove xprtsock's sysctls, unregister
> + */
> + if (clnt4)
> + rpc_shutdown_client(clnt4);
> + if (clnt)
> + rpc_shutdown_client(clnt);
> + }
> + return;
> +}
> +
> +static void rpcb_set_local(struct rpc_clnt *clnt, struct rpc_clnt *clnt4)
> +{
> + /* Protected by rpcb_create_local_mutex */
> + rpcb_local_clnt = clnt;
> + rpcb_local_clnt4 = clnt4;
> + rpcb_users++;
> + dprintk("RPC: created new rpcb local clients (rpcb_local_clnt: "
> + "%p, rpcb_local_clnt4: %p)\n", rpcb_local_clnt,
> + rpcb_local_clnt4);
> +}
> +
> /*
> * Returns zero on success, otherwise a negative errno value
> * is returned.
> --
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--
Jeff Layton <jlayton@xxxxxxxxxx>
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