From: Timo Sirainen <tss@iki.fi>
Date: Wed, 15 Dec 2010 17:07:01 +0000 (+0000)
Subject: master-child API change: Use a separate fd for tracking when master dies.
X-Git-Tag: 2.0.9~33
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cbcba924a745c938260fd39cb284175b75f8eaf2;p=thirdparty%2Fdovecot%2Fcore.git

master-child API change: Use a separate fd for tracking when master dies.
This works around a Linux performance problem where when one process writes
to status fd all the other processes of the same service type wake up.
---

diff --git a/src/lib-master/master-interface.h b/src/lib-master/master-interface.h
index 005abc5e87..2a6a79f62e 100644
--- a/src/lib-master/master-interface.h
+++ b/src/lib-master/master-interface.h
@@ -68,13 +68,16 @@ enum master_login_state {
 
 /* Shared pipe to master, used to send master_status reports */
 #define MASTER_STATUS_FD 5
+/* Pipe to master, used to detect when it dies. (MASTER_STATUS_FD would have
+   been fine for this, except it's inefficient in Linux) */
+#define MASTER_DEAD_FD 6
 /* First file descriptor where process is expected to be listening.
    The file descriptor count is given in -s parameter, defaulting to 1.
 
    master_status.available_count reports how many accept()s we're still
    accepting. Once no children are listening, master will do it and create
    new child processes when needed. */
-#define MASTER_LISTEN_FD_FIRST 6
+#define MASTER_LISTEN_FD_FIRST 7
 
 /* Timeouts: base everything on how long we can wait for login clients. */
 #define MASTER_LOGIN_TIMEOUT_SECS (3*60)
diff --git a/src/lib-master/master-service.c b/src/lib-master/master-service.c
index 5925bb63fb..250f479171 100644
--- a/src/lib-master/master-service.c
+++ b/src/lib-master/master-service.c
@@ -375,7 +375,7 @@ void master_service_init_finish(struct master_service *service)
 			master_service_set_service_count(service, count);
 
 		/* start listening errors for status fd, it means master died */
-		service->io_status_error = io_add(MASTER_STATUS_FD, IO_ERROR,
+		service->io_status_error = io_add(MASTER_DEAD_FD, IO_ERROR,
 						  master_status_error, service);
 	} else {
 		master_service_set_client_limit(service, 1);
diff --git a/src/master/common.h b/src/master/common.h
index ee7fc8beec..00ea6e17f6 100644
--- a/src/master/common.h
+++ b/src/master/common.h
@@ -9,7 +9,7 @@ extern uid_t master_uid;
 extern gid_t master_gid;
 extern bool core_dumps_disabled;
 extern const char *ssl_manual_key_password;
-extern int null_fd;
+extern int null_fd, master_dead_pipe_fd[2];
 extern struct service_list *services;
 
 void process_exec(const char *cmd, const char *extra_args[]) ATTR_NORETURN;
diff --git a/src/master/main.c b/src/master/main.c
index 350c9ca241..59bbec73a1 100644
--- a/src/master/main.c
+++ b/src/master/main.c
@@ -42,7 +42,7 @@ uid_t master_uid;
 gid_t master_gid;
 bool core_dumps_disabled;
 const char *ssl_manual_key_password;
-int null_fd;
+int null_fd, master_dead_pipe_fd[2];
 struct service_list *services;
 
 static char *pidfile_path;
@@ -412,7 +412,7 @@ static void main_init(const struct master_settings *set)
         lib_signals_set_handler(SIGUSR1, TRUE, sig_log_reopen, NULL);
         lib_signals_set_handler(SIGCHLD, TRUE, sig_reap_children, NULL);
         lib_signals_set_handler(SIGINT, TRUE, sig_die, NULL);
-        lib_signals_set_handler(SIGTERM, TRUE, sig_die, NULL);
+	lib_signals_set_handler(SIGTERM, TRUE, sig_die, NULL);
 
 	create_pid_file(pidfile_path);
 	create_config_symlink(set);
@@ -712,6 +712,10 @@ int main(int argc, char *argv[])
 			i_fatal("Can't open /dev/null: %m");
 		fd_close_on_exec(null_fd, TRUE);
 	} while (null_fd <= STDERR_FILENO);
+	if (pipe(master_dead_pipe_fd) < 0)
+		i_fatal("pipe() failed: %m");
+	fd_close_on_exec(master_dead_pipe_fd[0], TRUE);
+	fd_close_on_exec(master_dead_pipe_fd[1], TRUE);
 
 	set = master_settings_read();
 	if (ask_key_pass) {
diff --git a/src/master/service-process.c b/src/master/service-process.c
index de2a12ecd6..38d7f18e70 100644
--- a/src/master/service-process.c
+++ b/src/master/service-process.c
@@ -116,6 +116,7 @@ service_dup_fds(struct service *service)
 		break;
 	}
 	dup2_append(&dups, service->status_fd[1], MASTER_STATUS_FD);
+	dup2_append(&dups, master_dead_pipe_fd[1], MASTER_DEAD_FD);
 
 	if (service->type == SERVICE_TYPE_LOG) {
 		/* keep stderr as-is. this is especially important when