added option LWIP_NETCONN_SEM_PER_THREAD to use a semaphore per thread instead of using one per netconn and per select call

src/include/lwip/api.h

@@ -172,8 +172,10 @@ struct netconn {
   } pcb;
   /** the last error this netconn had */
   err_t last_err;
+#if !LWIP_NETCONN_SEM_PER_THREAD
   /** sem that is used to synchronously execute functions in the core context */
   sys_sem_t op_completed;
+#endif
   /** mbox where received packets are stored until they are fetched
       by the netconn application thread (can grow quite big) */
   sys_mbox_t recvmbox;
@@ -188,11 +190,11 @@ struct netconn {
 #endif /* LWIP_SOCKET */
 #if LWIP_SO_SNDTIMEO
   /** timeout to wait for sending data (which means enqueueing data for sending
-      in internal buffers) */
+      in internal buffers) in milliseconds */
   s32_t send_timeout;
 #endif /* LWIP_SO_RCVTIMEO */
 #if LWIP_SO_RCVTIMEO
-  /** timeout to wait for new data to be received
+  /** timeout in milliseconds to wait for new data to be received
       (or connections to arrive for listening netconns) */
   int recv_timeout;
 #endif /* LWIP_SO_RCVTIMEO */
@@ -329,6 +331,14 @@ err_t   netconn_gethostbyname(const char *name, ip_addr_t *addr);
 #define netconn_get_recvbufsize(conn)               ((conn)->recv_bufsize)
 #endif /* LWIP_SO_RCVBUF*/
 
+#if LWIP_NETCONN_SEM_PER_THREAD
+void netconn_thread_init(void);
+void netconn_thread_cleanup(void);
+#else /* LWIP_NETCONN_SEM_PER_THREAD */
+#define netconn_thread_init()
+#define netconn_thread_cleanup()
+#endif /* LWIP_NETCONN_SEM_PER_THREAD */
+
 #ifdef __cplusplus
 }
 #endif

src/include/lwip/api_msg.h

@@ -121,8 +121,18 @@ struct api_msg_msg {
     } lb;
 #endif /* TCP_LISTEN_BACKLOG */
   } msg;
+#if LWIP_NETCONN_SEM_PER_THREAD
+  sys_sem_t* op_completed_sem;
+#endif /* LWIP_NETCONN_SEM_PER_THREAD */
 };
 
+#if LWIP_NETCONN_SEM_PER_THREAD
+#define LWIP_API_MSG_SEM(msg)          ((msg)->op_completed_sem)
+#else /* LWIP_NETCONN_SEM_PER_THREAD */
+#define LWIP_API_MSG_SEM(msg)          (&(msg)->conn->op_completed)
+#endif /* LWIP_NETCONN_SEM_PER_THREAD */
+
+
 /** This struct contains a function to execute in another thread context and
     a struct api_msg_msg that serves as an argument for this function.
     This is passed to tcpip_apimsg to execute functions in tcpip_thread context. */

src/include/lwip/opt.h

@@ -1473,6 +1473,20 @@
 #define LWIP_TCPIP_TIMEOUT              1
 #endif
 
+/** LWIP_NETCONN_SEM_PER_THREAD==1: Use one (thread-local) semaphore per
+ * thread calling socket/netconn functions instead of allocating one
+ * semaphore per netconn (and per select etc.)
+ * ATTENTION: a thread-local semaphore for API calls is needed:
+ * - LWIP_NETCONN_THREAD_SEM_GET() returning a sys_sem_t*
+ * - LWIP_NETCONN_THREAD_SEM_ALLOC() creating the semaphore
+ * - LWIP_NETCONN_THREAD_SEM_FREE() freeing the semaphore
+ * The latter 2 can be invoked up by calling netconn_thread_init()/netconn_thread_cleanup().
+ * Ports may call these for threads created with sys_thread_new().
+ */
+#ifndef LWIP_NETCONN_SEM_PER_THREAD
+#define LWIP_NETCONN_SEM_PER_THREAD     0
+#endif
+
 /*
    ------------------------------------
    ---------- Socket options ----------

src/include/lwip/sockets.h

@@ -128,6 +128,10 @@ struct lwip_setgetsockopt_data {
   socklen_t *optlen;
   /** if an error occurs, it is temporarily stored here */
   err_t err;
+#if !LWIP_TCPIP_CORE_LOCKING
+  /** semaphore to wake up the calling task */
+  void* completed_sem;
+#endif /* !LWIP_TCPIP_CORE_LOCKING */
 };
 
 /* Socket protocol types (TCP/UDP/RAW) */

src/include/lwip/tcpip.h

@@ -65,8 +65,14 @@ extern sys_mutex_t lock_tcpip_core;
 #else
 #define TCIP_APIMSG_SET_ERR(m, e)
 #endif
+#if LWIP_NETCONN_SEM_PER_THREAD
+#define TCPIP_APIMSG_SET_SEM(m) ((m)->msg.op_completed_sem = LWIP_NETCONN_THREAD_SEM_GET())
+#else
+#define TCPIP_APIMSG_SET_SEM(m)
+#endif
 #define TCPIP_APIMSG_NOERR(m,f) do { \
   TCIP_APIMSG_SET_ERR(m, ERR_VAL); \
+  TCPIP_APIMSG_SET_SEM(m); \
   LOCK_TCPIP_CORE(); \
   f(&((m)->msg)); \
   UNLOCK_TCPIP_CORE(); \
@@ -85,7 +91,7 @@ extern sys_mutex_t lock_tcpip_core;
 #define UNLOCK_TCPIP_CORE()
 #define TCPIP_APIMSG_NOERR(m,f) do { (m)->function = f; tcpip_apimsg(m); } while(0)
 #define TCPIP_APIMSG(m,f,e)   do { (m)->function = f; (e) = tcpip_apimsg(m); } while(0)
-#define TCPIP_APIMSG_ACK(m)   sys_sem_signal(&m->conn->op_completed)
+#define TCPIP_APIMSG_ACK(m)   sys_sem_signal(LWIP_API_MSG_SEM(m))
 #define TCPIP_NETIFAPI(m)     tcpip_netifapi(m)
 #define TCPIP_NETIFAPI_ACK(m) sys_sem_signal(&m->sem)
 #define TCPIP_PPPAPI(m)       tcpip_pppapi(m)