transport: Add blocking recv calls to uhd-dpdk

This adds an internal wait queue API to uhd-dpdk. Socket configuration
requests had their blocking calls re-implemented on top of this API, and
it is also used to service requests to wait on RX packets (w/ timeout).

The wait API involves a multi-producer, single-consumer queue per I/O
thread (waiter_ring), with a condition variable used for sleeping. The
data structure is shared between user thread and I/O thread, and because
timeouts make resource release time non-deterministic, we use reference
counting on the shared resource.

One reference is generated by the user thread and passed to the I/O
thread to consume. A user thread that still needs the data after waking
must get() another reference, to postpone the destruction of the
resource until it is done.

Timeouts are based on CLOCK_MONOTONIC. For recv, a timeout of 0
indicates blocking indefinitely, and a negative timeout indicates no
timeout is desired.

Also drop timeout for closing sockets in uhd-dpdk.
The timeout would allow a user thread to pre-empt the I/O thread's
cleanup process. The user thread would free data structures the I/O
thread still needed to function. Since this timeout is superfluous
anyway, let's just get rid of it.

Also add some more input checking and error reporting.

1 files changed, 62 insertions, 0 deletions

diff --git a/host/lib/transport/uhd-dpdk/uhd_dpdk_wait.h b/host/lib/transport/uhd-dpdk/uhd_dpdk_wait.h
new file mode 100644
index 000000000..465608810
--- /dev/null
+++ b/host/lib/transport/uhd-dpdk/uhd_dpdk_wait.h
@@ -0,0 +1,62 @@
+//
+// Copyright 2018 Ettus Research, a National Instruments Company
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+//
+#ifndef _UHD_DPDK_WAIT_H_
+#define _UHD_DPDK_WAIT_H_
+
+#include "uhd_dpdk_ctx.h"
+#include <rte_malloc.h>
+
+enum uhd_dpdk_wait_type {
+    UHD_DPDK_WAIT_SIMPLE,
+    UHD_DPDK_WAIT_RX,
+    UHD_DPDK_WAIT_TX_BUF,
+    UHD_DPDK_WAIT_TYPE_COUNT
+};
+
+struct uhd_dpdk_wait_req {
+    enum uhd_dpdk_wait_type reason;
+    struct uhd_dpdk_socket *sock;
+    pthread_cond_t cond;
+    pthread_mutex_t mutex;
+    rte_atomic32_t refcnt; /* free resources only when refcnt = 0 */
+};
+
+static inline void uhd_dpdk_waiter_put(struct uhd_dpdk_wait_req *req)
+{
+    if (rte_atomic32_dec_and_test(&req->refcnt)) {
+        rte_free(req);
+    }
+}
+
+static inline void uhd_dpdk_waiter_get(struct uhd_dpdk_wait_req *req)
+{
+    rte_atomic32_inc(&req->refcnt);
+}
+
+/*
+ * Attempt to wake thread
+ * Re-enqueue waiter to thread's waiter_queue if fail
+ */
+int _uhd_dpdk_waiter_wake(struct uhd_dpdk_wait_req *req,
+                          struct uhd_dpdk_thread *t);
+
+/*
+ * Allocates wait request and sets refcnt to 1
+ */
+struct uhd_dpdk_wait_req *uhd_dpdk_waiter_alloc(enum uhd_dpdk_wait_type reason);
+
+/*
+ * Block and send wait request to thread t
+ */
+int uhd_dpdk_waiter_wait(struct uhd_dpdk_wait_req *req, int timeout,
+                         struct uhd_dpdk_thread *t);
+
+/*
+ * Block and submit config request to thread t
+ */
+int uhd_dpdk_config_req_submit(struct uhd_dpdk_config_req *req,
+                               int timeout, struct uhd_dpdk_thread *t);
+#endif /* _UHD_DPDK_WAIT_H_ */