On Fri, May 01, 2020 at 01:22:27PM -0400, Chuck Lever wrote:
> - Rename these so they are easy to enable and search for as a set
> - Move the tracepoints to get a more accurate sense of control flow
> - Tracepoints should not fire on xprt shutdown
> - Display memory address in case data structure had been corrupted
> - Abandon dprintk in these paths
>
> I haven't ever gotten one of these tracepoints to trigger. I wonder
> if we should simply remove them.
It's definitely not dead code. But I forget the conditions required to
hit those cases. Looking.... So, we in cache_check we have a cache miss
that requires an upcall, and call cache_defer_req, which will wait for a
response 1 or 5 seconds (depending on how busy server threads are) and
then calls svc_defer().
--b.
>
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
> include/trace/events/sunrpc.h | 11 ++++++++---
> net/sunrpc/svc_xprt.c | 12 ++++++------
> 2 files changed, 14 insertions(+), 9 deletions(-)
>
> diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h
> index ffd2215950dc..3158b3f7e01e 100644
> --- a/include/trace/events/sunrpc.h
> +++ b/include/trace/events/sunrpc.h
> @@ -1313,27 +1313,32 @@ DECLARE_EVENT_CLASS(svc_deferred_event,
> TP_ARGS(dr),
>
> TP_STRUCT__entry(
> + __field(const void *, dr)
> __field(u32, xid)
> __string(addr, dr->xprt->xpt_remotebuf)
> ),
>
> TP_fast_assign(
> + __entry->dr = dr;
> __entry->xid = be32_to_cpu(*(__be32 *)(dr->args +
> (dr->xprt_hlen>>2)));
> __assign_str(addr, dr->xprt->xpt_remotebuf);
> ),
>
> - TP_printk("addr=%s xid=0x%08x", __get_str(addr), __entry->xid)
> + TP_printk("addr=%s dr=%p xid=0x%08x", __get_str(addr), __entry->dr,
> + __entry->xid)
> );
> +
> #define DEFINE_SVC_DEFERRED_EVENT(name) \
> - DEFINE_EVENT(svc_deferred_event, svc_##name##_deferred, \
> + DEFINE_EVENT(svc_deferred_event, svc_defer_##name, \
> TP_PROTO( \
> const struct svc_deferred_req *dr \
> ), \
> TP_ARGS(dr))
>
> DEFINE_SVC_DEFERRED_EVENT(drop);
> -DEFINE_SVC_DEFERRED_EVENT(revisit);
> +DEFINE_SVC_DEFERRED_EVENT(queue);
> +DEFINE_SVC_DEFERRED_EVENT(recv);
>
> DECLARE_EVENT_CLASS(cache_event,
> TP_PROTO(
> diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
> index 2284ff038dad..e12ec68cd0ff 100644
> --- a/net/sunrpc/svc_xprt.c
> +++ b/net/sunrpc/svc_xprt.c
> @@ -1158,16 +1158,15 @@ static void svc_revisit(struct cache_deferred_req *dreq, int too_many)
> set_bit(XPT_DEFERRED, &xprt->xpt_flags);
> if (too_many || test_bit(XPT_DEAD, &xprt->xpt_flags)) {
> spin_unlock(&xprt->xpt_lock);
> - dprintk("revisit canceled\n");
> + trace_svc_defer_drop(dr);
> svc_xprt_put(xprt);
> - trace_svc_drop_deferred(dr);
> kfree(dr);
> return;
> }
> - dprintk("revisit queued\n");
> dr->xprt = NULL;
> list_add(&dr->handle.recent, &xprt->xpt_deferred);
> spin_unlock(&xprt->xpt_lock);
> + trace_svc_defer_queue(dr);
> svc_xprt_enqueue(xprt);
> svc_xprt_put(xprt);
> }
> @@ -1213,22 +1212,24 @@ static struct cache_deferred_req *svc_defer(struct cache_req *req)
> memcpy(dr->args, rqstp->rq_arg.head[0].iov_base - skip,
> dr->argslen << 2);
> }
> + trace_svc_defer(rqstp);
> svc_xprt_get(rqstp->rq_xprt);
> dr->xprt = rqstp->rq_xprt;
> set_bit(RQ_DROPME, &rqstp->rq_flags);
>
> dr->handle.revisit = svc_revisit;
> - trace_svc_defer(rqstp);
> return &dr->handle;
> }
>
> /*
> * recv data from a deferred request into an active one
> */
> -static int svc_deferred_recv(struct svc_rqst *rqstp)
> +static noinline int svc_deferred_recv(struct svc_rqst *rqstp)
> {
> struct svc_deferred_req *dr = rqstp->rq_deferred;
>
> + trace_svc_defer_recv(dr);
> +
> /* setup iov_base past transport header */
> rqstp->rq_arg.head[0].iov_base = dr->args + (dr->xprt_hlen>>2);
> /* The iov_len does not include the transport header bytes */
> @@ -1259,7 +1260,6 @@ static struct svc_deferred_req *svc_deferred_dequeue(struct svc_xprt *xprt)
> struct svc_deferred_req,
> handle.recent);
> list_del_init(&dr->handle.recent);
> - trace_svc_revisit_deferred(dr);
> } else
> clear_bit(XPT_DEFERRED, &xprt->xpt_flags);
> spin_unlock(&xprt->xpt_lock);
