On Sat, Oct 29, 2016 at 12:21:03PM -0400, Chuck Lever wrote:
> Hi Bruce-
Sorry for the slow response!
...
> In commit 39a9beab5acb83176e8b9a4f0778749a09341f1f ('rpc: share one xps between
> all backchannels') you added:
>
> diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
> index f5572e3..4f01f63 100644
> --- a/net/sunrpc/svc_xprt.c
> +++ b/net/sunrpc/svc_xprt.c
> @@ -136,6 +136,8 @@ static void svc_xprt_free(struct kref *kref)
> /* See comment on corresponding get in xs_setup_bc_tcp(): */
> if (xprt->xpt_bc_xprt)
> xprt_put(xprt->xpt_bc_xprt);
> + if (xprt->xpt_bc_xps)
> + xprt_switch_put(xprt->xpt_bc_xps);
> xprt->xpt_ops->xpo_free(xprt);
> module_put(owner);
> }
>
> svc_xprt_free() is invoked by svc_xprt_put(). svc_xprt_put() is called
> from svc_rdma in soft IRQ context (eg. svc_rdma_wc_receive).
Is that necessary? I wonder why the svcrdma code seems to be taking so
many of its own references on svc_xprts.
> However, xprt_switch_put() takes a spin lock (xps_lock) which is locked
> everywhere without disabling BHs.
>
> It looks to me like 39a9beab5acb makes svc_xprt_put() no longer BH-safe?
> Not sure if svc_xprt_put() was intended to be BH-safe beforehand.
>
> Maybe xprt_switch_put() could be invoked in ->xpo_free, but that seems
> like a temporary solution.
Since xpo_free is also called from svc_xprt_put that doesn't sound like
it would change anything. Or do we not trunk over RDMA for some reason?
--b.
>
>
> --
> Chuck Lever
>
>
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