Improve handling of poll lists (fix issue #159).

Removal of elements and shrinking of poll lists are now performed at
separate times, so as to simplify execution logic. In particular, early
exit of the main loop is no longer needed.

src/server/server-unix.c

@@ -98,6 +98,7 @@ void add_to_poll_list(int sock, short events) {
   }
   poll_list[poll_num].fd = sock;
   poll_list[poll_num].events = events;
+  poll_list[poll_num].revents = 0;
   poll_num++;
 }
 
@@ -110,19 +111,24 @@ struct pollfd* poll_list_lookup(int fd) {
   return NULL;
 }
 
+void poll_list_clean() {
+  int i = 0;
+  while (i < poll_num) {
+    if (poll_list[i].fd == -1) {
+      poll_list[i] = poll_list[poll_num - 1];
+      --poll_num;
+    } else ++i;
+  }
+}
+
 void poll_list_remove(int fd) {
-  int i;
-  assert (poll_num > 0);
-  for (i = 0; i < poll_num; i++) {
+  for (int i = 0; i < poll_num; ++i) {
     if (poll_list[i].fd == fd) {
+      poll_list[i].fd = -1;
+      poll_list[i].revents = 0;
       break;
     }
   }
-  if (i == poll_num) {
-    return;
-  }
-  poll_list[i] = poll_list[poll_num - 1];
-  poll_num--;
 }
 
 int open_temp_file(char* dir, char** outfile) {
@@ -597,6 +603,7 @@ int main(int argc, char **argv) {
   server_init_listening(socketname, parallel);
   while (1) {
     schedule_new_jobs();
+    poll_list_clean();
     while ((res = poll(poll_list, poll_num, -1)) == -1 && errno == EINTR)
       continue;
     if (res == -1) {
@@ -621,9 +628,7 @@ int main(int argc, char **argv) {
       if (cur->fd == server_sock) {
         assert (cur->revents == POLLIN);
         server_accept_client();
-        //we should stop looking at other sockets now, because we have altered
-        //the poll list
-        break;
+        continue;
       }
 
       // a client
@@ -632,8 +637,7 @@ int main(int argc, char **argv) {
         continue;
       if (cur->revents & POLLERR) {
         close_client(client);
-      }
-      if (cur->revents & POLLOUT) {
+      } else if (cur->revents & POLLOUT) {
         write_to_client(client, cur);
       } else if (cur->revents & POLLIN) {
         read_on_client(client);