[PATCH net-next 11/12] rxrpc: Add a tracepoint to track rxrpc_peer refcounting

From: David Howells
Date: Fri Mar 30 2018 - 17:15:22 EST


Add a tracepoint to track reference counting on the rxrpc_peer struct.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---

include/trace/events/rxrpc.h | 42 +++++++++++++++++++++++++++
net/rxrpc/ar-internal.h | 23 +++------------
net/rxrpc/peer_event.c | 2 +
net/rxrpc/peer_object.c | 65 +++++++++++++++++++++++++++++++++++++++++-
4 files changed, 110 insertions(+), 22 deletions(-)

diff --git a/include/trace/events/rxrpc.h b/include/trace/events/rxrpc.h
index 0410dfeb79c6..9e96c2fe2793 100644
--- a/include/trace/events/rxrpc.h
+++ b/include/trace/events/rxrpc.h
@@ -50,6 +50,14 @@ enum rxrpc_local_trace {
rxrpc_local_queued,
};

+enum rxrpc_peer_trace {
+ rxrpc_peer_got,
+ rxrpc_peer_new,
+ rxrpc_peer_processing,
+ rxrpc_peer_put,
+ rxrpc_peer_queued_error,
+};
+
enum rxrpc_conn_trace {
rxrpc_conn_got,
rxrpc_conn_new_client,
@@ -230,6 +238,13 @@ enum rxrpc_congest_change {
EM(rxrpc_local_put, "PUT") \
E_(rxrpc_local_queued, "QUE")

+#define rxrpc_peer_traces \
+ EM(rxrpc_peer_got, "GOT") \
+ EM(rxrpc_peer_new, "NEW") \
+ EM(rxrpc_peer_processing, "PRO") \
+ EM(rxrpc_peer_put, "PUT") \
+ E_(rxrpc_peer_queued_error, "QER")
+
#define rxrpc_conn_traces \
EM(rxrpc_conn_got, "GOT") \
EM(rxrpc_conn_new_client, "NWc") \
@@ -482,6 +497,33 @@ TRACE_EVENT(rxrpc_local,
__entry->where)
);

+TRACE_EVENT(rxrpc_peer,
+ TP_PROTO(struct rxrpc_peer *peer, enum rxrpc_peer_trace op,
+ int usage, const void *where),
+
+ TP_ARGS(peer, op, usage, where),
+
+ TP_STRUCT__entry(
+ __field(unsigned int, peer )
+ __field(int, op )
+ __field(int, usage )
+ __field(const void *, where )
+ ),
+
+ TP_fast_assign(
+ __entry->peer = peer->debug_id;
+ __entry->op = op;
+ __entry->usage = usage;
+ __entry->where = where;
+ ),
+
+ TP_printk("P=%08x %s u=%d sp=%pSR",
+ __entry->peer,
+ __print_symbolic(__entry->op, rxrpc_peer_traces),
+ __entry->usage,
+ __entry->where)
+ );
+
TRACE_EVENT(rxrpc_conn,
TP_PROTO(struct rxrpc_connection *conn, enum rxrpc_conn_trace op,
int usage, const void *where),
diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index d40d54b78567..c46583bc255d 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -1041,25 +1041,10 @@ struct rxrpc_peer *rxrpc_lookup_peer(struct rxrpc_local *,
struct rxrpc_peer *rxrpc_alloc_peer(struct rxrpc_local *, gfp_t);
struct rxrpc_peer *rxrpc_lookup_incoming_peer(struct rxrpc_local *,
struct rxrpc_peer *);
-
-static inline struct rxrpc_peer *rxrpc_get_peer(struct rxrpc_peer *peer)
-{
- atomic_inc(&peer->usage);
- return peer;
-}
-
-static inline
-struct rxrpc_peer *rxrpc_get_peer_maybe(struct rxrpc_peer *peer)
-{
- return atomic_inc_not_zero(&peer->usage) ? peer : NULL;
-}
-
-extern void __rxrpc_put_peer(struct rxrpc_peer *peer);
-static inline void rxrpc_put_peer(struct rxrpc_peer *peer)
-{
- if (peer && atomic_dec_and_test(&peer->usage))
- __rxrpc_put_peer(peer);
-}
+struct rxrpc_peer *rxrpc_get_peer(struct rxrpc_peer *);
+struct rxrpc_peer *rxrpc_get_peer_maybe(struct rxrpc_peer *);
+void rxrpc_put_peer(struct rxrpc_peer *);
+void __rxrpc_queue_peer_error(struct rxrpc_peer *);

/*
* proc.c
diff --git a/net/rxrpc/peer_event.c b/net/rxrpc/peer_event.c
index d01eb9a06448..78c2f95d1f22 100644
--- a/net/rxrpc/peer_event.c
+++ b/net/rxrpc/peer_event.c
@@ -192,7 +192,7 @@ void rxrpc_error_report(struct sock *sk)
rxrpc_free_skb(skb, rxrpc_skb_rx_freed);

/* The ref we obtained is passed off to the work item */
- rxrpc_queue_work(&peer->error_distributor);
+ __rxrpc_queue_peer_error(peer);
_leave("");
}

diff --git a/net/rxrpc/peer_object.c b/net/rxrpc/peer_object.c
index 94a6dbfcf129..a4a750aea1e5 100644
--- a/net/rxrpc/peer_object.c
+++ b/net/rxrpc/peer_object.c
@@ -386,9 +386,54 @@ struct rxrpc_peer *rxrpc_lookup_peer(struct rxrpc_local *local,
}

/*
- * Discard a ref on a remote peer record.
+ * Get a ref on a peer record.
*/
-void __rxrpc_put_peer(struct rxrpc_peer *peer)
+struct rxrpc_peer *rxrpc_get_peer(struct rxrpc_peer *peer)
+{
+ const void *here = __builtin_return_address(0);
+ int n;
+
+ n = atomic_inc_return(&peer->usage);
+ trace_rxrpc_peer(peer, rxrpc_peer_got, n, here);
+ return peer;
+}
+
+/*
+ * Get a ref on a peer record unless its usage has already reached 0.
+ */
+struct rxrpc_peer *rxrpc_get_peer_maybe(struct rxrpc_peer *peer)
+{
+ const void *here = __builtin_return_address(0);
+
+ if (peer) {
+ int n = __atomic_add_unless(&peer->usage, 1, 0);
+ if (n > 0)
+ trace_rxrpc_peer(peer, rxrpc_peer_got, n + 1, here);
+ else
+ peer = NULL;
+ }
+ return peer;
+}
+
+/*
+ * Queue a peer record. This passes the caller's ref to the workqueue.
+ */
+void __rxrpc_queue_peer_error(struct rxrpc_peer *peer)
+{
+ const void *here = __builtin_return_address(0);
+ int n;
+
+ n = atomic_read(&peer->usage);
+ if (rxrpc_queue_work(&peer->error_distributor))
+ trace_rxrpc_peer(peer, rxrpc_peer_queued_error, n, here);
+ else
+ rxrpc_put_peer(peer);
+}
+
+/*
+ * Discard a peer record.
+ */
+static void __rxrpc_put_peer(struct rxrpc_peer *peer)
{
struct rxrpc_net *rxnet = peer->local->rxnet;

@@ -402,6 +447,22 @@ void __rxrpc_put_peer(struct rxrpc_peer *peer)
kfree_rcu(peer, rcu);
}

+/*
+ * Drop a ref on a peer record.
+ */
+void rxrpc_put_peer(struct rxrpc_peer *peer)
+{
+ const void *here = __builtin_return_address(0);
+ int n;
+
+ if (peer) {
+ n = atomic_dec_return(&peer->usage);
+ trace_rxrpc_peer(peer, rxrpc_peer_put, n, here);
+ if (n == 0)
+ __rxrpc_put_peer(peer);
+ }
+}
+
/**
* rxrpc_kernel_get_peer - Get the peer address of a call
* @sock: The socket on which the call is in progress.