HI,

The MHD goes in a busy loop when it is configured with MHD_USE_POLL_INTERNALLY and a connection times out.
When the connection times out, the connection is closed at connection.c:2646, which sets connection->event_loop_info = MHD_EVENT_LOOP_INFO_CLEANUP.
When the loop info is set to MHD_EVENT_LOOP_INFO_CLEANUP, the main function of the thread loop, MHD_poll_all, never calls back the connection idle callback, which would have cleaned the connection and exit the loop.
I resolved the issue in my development code by adding pos->idle_handler (pos) at daemon.c:2477 in MHD_poll_all (SVN 35533).

The busy loop could be tested using a small enough connection timeout and netcat:
nc -v -w 100 <IP ADDRESS> <IP PORT>

CPU usage will reach 100% in one of the CPU and will remain at that level even when the netcat has closed its end of the connection.

Thanks,

Louis Benoit

AUTHORS

@@ -53,6 +53,7 @@ Hani Benhabiles <kroosec@gmail.com>
 Guy Martin <gmsoft@tuxicoman.be>
 Robert Groenenberg <robert.groenenberg@broadforward.com>
 Denis Dowling <denis.dowling@hsd.com.au>
+Louis Benoit <louisbenoit@videotron.ca>
 
 
 Documentation contributions also came from:

ChangeLog

@@ -1,3 +1,7 @@
+Wed Apr 15 00:30:34 CEST 2015
+	Fix looping issue when using MHD_USE_POLL_INTERNALLY
+	and a client times out. -LB
+
 Sun Apr 12 21:48:50 CEST 2015
 	Fix looping issue when combining MHD_USE_EPOLL_LINUX_ONLY
 	with HTTPS and slow clients. -CG

src/include/microhttpd.h

@@ -130,7 +130,7 @@ typedef intptr_t ssize_t;
  * Current version of the library.
  * 0x01093001 = 1.9.30-1.
  */
-#define MHD_VERSION 0x00094004
+#define MHD_VERSION 0x00094005
 
 /**
  * MHD-internal return code for "YES".

src/microhttpd/daemon.c

@@ -2474,7 +2474,7 @@ MHD_poll_all (struct MHD_Daemon *daemon,
 	    pos->idle_handler (pos);
 	    break;
 	  case MHD_EVENT_LOOP_INFO_CLEANUP:
-	    /* should never happen */
+	    pos->idle_handler (pos);
 	    break;
 	  }
       }