signal: refactoring, add comments in tcp_server, etc.

5 files changed, 38 insertions, 26 deletions

diff --git a/src/server.c b/src/server.c
index 67f9e17..3df1f7d 100644
--- a/src/server.c
+++ b/src/server.c
@@ -213,7 +213,7 @@ int server_create(struct server **_server, const struct settings *settings)
 	struct storage_settings storage_settings;
 	int ret = 0;
 
-	ret = signal_install_global_handler();
+	ret = signal_handle_stop_signals();
 	if (ret < 0)
 		return ret;
 
diff --git a/src/signal.c b/src/signal.c
index ecf45ca..0676e60 100644
--- a/src/signal.c
+++ b/src/signal.c
@@ -10,8 +10,11 @@
 #include "log.h"
 
 #include <signal.h>
+#include <stddef.h>
 #include <string.h>
 
+static int stop_signals[] = {SIGINT, SIGTERM, SIGQUIT};
+
 volatile sig_atomic_t global_stop_flag = 0;
 
 static void set_global_stop_flag(UNUSED int signum)
@@ -32,7 +35,7 @@ static int my_sigaction(int signo, const struct sigaction *act)
 	return ret;
 }
 
-int signal_install_global_handler(void)
+int signal_handle_stop_signals(void)
 {
 	int ret = 0;
 
@@ -42,20 +45,17 @@ int signal_install_global_handler(void)
 
 	/* Don't care about proper cleanup here; we exit the program if this
 	 * fails anyway. */
-	ret = my_sigaction(SIGINT, &sa);
-	if (ret < 0)
-		return ret;
-	ret = my_sigaction(SIGQUIT, &sa);
-	if (ret < 0)
-		return ret;
-	ret = my_sigaction(SIGTERM, &sa);
-	if (ret < 0)
-		return ret;
+
+	for (size_t i = 0; i < sizeof(stop_signals) / sizeof(stop_signals[0]); ++i) {
+		ret = my_sigaction(stop_signals[i], &sa);
+		if (ret < 0)
+			return ret;
+	}
 
 	return ret;
 }
 
-int signal_set(const sigset_t *new, sigset_t *old)
+static int signal_set(const sigset_t *new, sigset_t *old)
 {
 	int ret = 0;
 
@@ -68,19 +68,25 @@ int signal_set(const sigset_t *new, sigset_t *old)
 	return ret;
 }
 
-int signal_block_parent(sigset_t *old)
+int signal_block_all(sigset_t *old)
 {
 	sigset_t new;
 	sigfillset(&new);
 	return signal_set(&new, old);
 }
 
-int signal_block_child(void)
+int signal_restore(const sigset_t *new)
+{
+	return signal_set(new, NULL);
+}
+
+int signal_unblock_all_except_stop_signals(void)
 {
 	sigset_t set;
 	sigemptyset(&set);
-	sigaddset(&set, SIGINT);
-	sigaddset(&set, SIGQUIT);
-	sigaddset(&set, SIGTERM);
+
+	for (size_t i = 0; i < sizeof(stop_signals) / sizeof(stop_signals[0]); ++i)
+		sigaddset(&set, stop_signals[i]);
+
 	return signal_set(&set, NULL);
 }
diff --git a/src/signal.h b/src/signal.h
index 88c9734..713c842 100644
--- a/src/signal.h
+++ b/src/signal.h
@@ -11,11 +11,11 @@
 #include <signal.h>
 
 extern volatile sig_atomic_t global_stop_flag;
-int signal_install_global_handler(void);
+int signal_handle_stop_signals(void);
 
-int signal_set(const sigset_t *new, sigset_t *old);
+int signal_block_all(sigset_t *old);
+int signal_restore(const sigset_t *new);
 
-int signal_block_parent(sigset_t *old);
-int signal_block_child(void);
+int signal_unblock_all_except_stop_signals(void);
 
 #endif
diff --git a/src/tcp_server.c b/src/tcp_server.c
index d840414..dbf1146 100644
--- a/src/tcp_server.c
+++ b/src/tcp_server.c
@@ -60,7 +60,9 @@ static void *connection_thread(void *_ctx)
 	struct child_context *ctx = (struct child_context *)_ctx;
 	int ret = 0;
 
-	ret = signal_block_child();
+	/* Let the child thread handle its signals except those that should be
+	 * handled in the main thread. */
+	ret = signal_unblock_all_except_stop_signals();
 	if (ret < 0)
 		goto free_ctx;
 
@@ -92,7 +94,10 @@ int tcp_server_accept(const struct tcp_server *server, tcp_server_conn_handler h
 		goto free_ctx;
 	ctx->fd = ret;
 
-	ret = signal_block_parent(&old_mask);
+	/* Block all signals (we'll unblock them later); the child thread will
+	 * have all signals blocked initially. This allows the main thread to
+	 * handle SIGINT/SIGTERM/etc. */
+	ret = signal_block_all(&old_mask);
 	if (ret < 0)
 		goto close_conn;
 
@@ -102,12 +107,13 @@ int tcp_server_accept(const struct tcp_server *server, tcp_server_conn_handler h
 		goto restore_mask;
 	}
 
-	signal_set(&old_mask, NULL);
+	/* Restore the previously-enabled signals for handling in the main thread. */
+	signal_restore(&old_mask);
 
 	return ret;
 
 restore_mask:
-	signal_set(&old_mask, NULL);
+	signal_restore(&old_mask);
 
 close_conn:
 	log_errno_if(close(ctx->fd), "close");
diff --git a/src/worker.c b/src/worker.c
index a316d7f..d085000 100644
--- a/src/worker.c
+++ b/src/worker.c
@@ -27,7 +27,7 @@ int worker_create(struct worker **_worker)
 {
 	int ret = 0;
 
-	ret = signal_install_global_handler();
+	ret = signal_handle_stop_signals();
 	if (ret < 0)
 		return ret;