Patch from Eric Norum <eric@skatter.usask.ca>:

Remember the test to see if a socket could be read and written at
    the same time by two different tasks?  I discovered that if both
    tasks attempt to close the socket a panic can occur from inside the
    BSD code.

    Closing the same socket twice from two different threads is
    certainly an error, but a panic is not the greatest error reporting
    method :-)

    The following small change to the socket close routine should reduce
    the chances of the panic.

c/src/exec/libnetworking/rtems/rtems_syscall.c

@@ -683,16 +683,15 @@ rtems_bsdnet_close (int fd)
 		rtems_bsdnet_semaphore_release ();
 		return -1;
 	}
-	error = soclose (so);
 	i = rtems_file_descriptor_base(fd);
 	fdsock[i].indexFreeNext = indexFreeHead;;
 	indexFreeHead = i;
+	error = soclose (so);
+	rtems_bsdnet_semaphore_release ();
 	if (error) {
 		errno = error;
-		rtems_bsdnet_semaphore_release ();
 		return -1;
 	}
-	rtems_bsdnet_semaphore_release ();
 	return 0;
 }
 

c/src/lib/libnetworking/rtems/rtems_syscall.c

@@ -683,16 +683,15 @@ rtems_bsdnet_close (int fd)
 		rtems_bsdnet_semaphore_release ();
 		return -1;
 	}
-	error = soclose (so);
 	i = rtems_file_descriptor_base(fd);
 	fdsock[i].indexFreeNext = indexFreeHead;;
 	indexFreeHead = i;
+	error = soclose (so);
+	rtems_bsdnet_semaphore_release ();
 	if (error) {
 		errno = error;
-		rtems_bsdnet_semaphore_release ();
 		return -1;
 	}
-	rtems_bsdnet_semaphore_release ();
 	return 0;
 }
 

c/src/libnetworking/rtems/rtems_syscall.c

@@ -683,16 +683,15 @@ rtems_bsdnet_close (int fd)
 		rtems_bsdnet_semaphore_release ();
 		return -1;
 	}
-	error = soclose (so);
 	i = rtems_file_descriptor_base(fd);
 	fdsock[i].indexFreeNext = indexFreeHead;;
 	indexFreeHead = i;
+	error = soclose (so);
+	rtems_bsdnet_semaphore_release ();
 	if (error) {
 		errno = error;
-		rtems_bsdnet_semaphore_release ();
 		return -1;
 	}
-	rtems_bsdnet_semaphore_release ();
 	return 0;
 }