use signalfd to stop on SIGTERM

Is this an overkill? I don't know.

The thing is, correctly intercepting SIGTERM (also SIGINT, etc.) is
incredibly tricky. For example, before this commit, my I/O loops in
server.c and worker.c were inherently racy.

This was immediately obvious if you tried to run the tests. The tests
(especially the Valgrind flavour) would run a worker, wait until it
prints a "Waiting for a new command" line, and try to kill it using
SIGTERM. The problem is, the global_stop_flag check could have already
been executed by the worker, and it would hang forever in recv().

The solution seems to be to use signalfd and select()/poll(). I've never
used either before, but it seems to work well enough - at least the very
same tests pass and don't hang now.

1 files changed, 8 insertions, 3 deletions

diff --git a/src/tcp_server.h b/src/tcp_server.h
index 0f377d8..f96e3f1 100644
--- a/src/tcp_server.h
+++ b/src/tcp_server.h
@@ -8,12 +8,17 @@
 #ifndef __TCP_SERVER_H__
 #define __TCP_SERVER_H__
 
+#include "event_loop.h"
+
 struct tcp_server;
 
-int tcp_server_create(struct tcp_server **, const char *port);
+typedef int (*tcp_server_conn_handler)(int conn_fd, void *arg);
+
+int tcp_server_create(struct tcp_server **, const char *port, tcp_server_conn_handler, void *arg);
 void tcp_server_destroy(struct tcp_server *);
 
-typedef int (*tcp_server_conn_handler)(int conn_fd, void *arg);
-int tcp_server_accept(const struct tcp_server *, tcp_server_conn_handler, void *arg);
+int tcp_server_accept(const struct tcp_server *);
+
+int tcp_server_add_to_event_loop(struct tcp_server *, struct event_loop *);
 
 #endif