From b161682adc49442ce9c424513cb2763ee10896ba Mon Sep 17 00:00:00 2001
From: zhangyuan7 <zhangyuan7@pinecone.net>
Date: Tue, 19 Mar 2019 09:23:08 -0600
Subject: [PATCH] net/usrsock:  Add mutual exclusion so that only user can
 perform a socket request

---
 net/usrsock/usrsock.h      |  2 ++
 net/usrsock/usrsock_conn.c | 16 ++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/net/usrsock/usrsock.h b/net/usrsock/usrsock.h
index 44629a80f0..efb9268b45 100644
--- a/net/usrsock/usrsock.h
+++ b/net/usrsock/usrsock.h
@@ -100,6 +100,7 @@ struct usrsock_conn_s
 
   struct
   {
+    sem_t    sem;         /* Request semaphore (only one outstanding request) */
     uint8_t  xid;         /* Expected message exchange id */
     bool     inprogress;  /* Request was received but daemon is still processing */
     uint16_t valuelen;    /* Length of value from daemon */
@@ -127,6 +128,7 @@ struct usrsock_reqstate_s
   sem_t                   recvsem;   /* Semaphore signals recv completion */
   int                     result;    /* OK on success, otherwise a negated errno. */
   bool                    completed;
+  bool                    unlock;    /* True: unlock is required */
 };
 
 struct usrsock_data_reqstate_s
diff --git a/net/usrsock/usrsock_conn.c b/net/usrsock/usrsock_conn.c
index cdc3c71660..a80251d509 100644
--- a/net/usrsock/usrsock_conn.c
+++ b/net/usrsock/usrsock_conn.c
@@ -131,6 +131,7 @@ FAR struct usrsock_conn_s *usrsock_alloc(void)
       /* Make sure that the connection is marked as uninitialized */
 
       memset(conn, 0, sizeof(*conn));
+      nxsem_init(&conn->resp.sem, 0, 1);
       conn->dev = NULL;
       conn->usockid = -1;
       conn->state = USRSOCK_CONN_STATE_UNINITIALIZED;
@@ -169,6 +170,7 @@ void usrsock_free(FAR struct usrsock_conn_s *conn)
 
   /* Reset structure */
 
+  nxsem_destroy(&conn->resp.sem);
   memset(conn, 0, sizeof(*conn));
   conn->dev = NULL;
   conn->usockid = -1;
@@ -259,12 +261,21 @@ int usrsock_setup_request_callback(FAR struct usrsock_conn_s *conn,
   pstate->conn   = conn;
   pstate->result = -EAGAIN;
   pstate->completed = false;
+  pstate->unlock = false;
 
   /* Set up the callback in the connection */
 
   pstate->cb = devif_callback_alloc(NULL, &conn->list);
   if (pstate->cb)
     {
+      /* Take a lock since only one outstanding request is allowed */
+
+      if ((flags & USRSOCK_EVENT_REQ_COMPLETE) != 0)
+        {
+          _usrsock_semtake(&conn->resp.sem);
+          pstate->unlock = true;
+        }
+
       /* Set up the connection event handler */
 
       pstate->cb->flags = flags;
@@ -300,6 +311,11 @@ void usrsock_teardown_request_callback(FAR struct usrsock_reqstate_s *pstate)
 {
   FAR struct usrsock_conn_s *conn = pstate->conn;
 
+  if (pstate->unlock)
+    {
+      _usrsock_semgive(&conn->resp.sem);
+    }
+
   /* Make sure that no further events are processed */
 
   devif_conn_callback_free(NULL, pstate->cb, &conn->list);