From: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Date: Mon, 10 Jan 2011 02:57:49 +0000 (+1100)
Subject: Add ctdb_fork(0 which will fork a child process and drop the real-time
X-Git-Url: http://git.samba.org/?p=sahlberg%2Fctdb.git;a=commitdiff_plain;h=ebbebeec3b511ffb66bca506abc1bb867911ae95

Add ctdb_fork(0 which will fork a child process and drop the real-time
scheduler for the child.

Use ctdb_fork() from callers where we dont want the child to be running
at real-time privilege.
---

diff --git a/common/ctdb_logging.c b/common/ctdb_logging.c
index de6e039d..dee4dfdb 100644
--- a/common/ctdb_logging.c
+++ b/common/ctdb_logging.c
@@ -157,7 +157,7 @@ int32_t ctdb_control_get_log(struct ctdb_context *ctdb, TDB_DATA addr)
 	/* spawn a child process to marshall the huge log blob and send it back
 	   to the ctdb tool using a MESSAGE
 	*/
-	child = fork();
+	child = ctdb_fork(ctdb);
 	if (child == (pid_t)-1) {
 		DEBUG(DEBUG_ERR,("Failed to fork a log collector child\n"));
 		return -1;
diff --git a/common/ctdb_util.c b/common/ctdb_util.c
index 80390899..1ff4c1f9 100644
--- a/common/ctdb_util.c
+++ b/common/ctdb_util.c
@@ -334,15 +334,20 @@ void ctdb_restore_scheduler(struct ctdb_context *ctdb)
 }
 
 /*
-  make ourselves slightly nicer: eg. a ctdb child.
+ * This function forks a child process and drops the realtime 
+ * scheduler for the child process.
  */
-void ctdb_reduce_priority(struct ctdb_context *ctdb)
+pid_t ctdb_fork(struct ctdb_context *ctdb)
 {
-	errno = 0;
-	if (nice(10) == -1 && errno != 0) {
-		DEBUG(DEBUG_WARNING,("Unable to lower priority: %s\n",
-				     strerror(errno)));
+	pid_t pid;
+
+	pid = fork();
+	if (pid == 0) {
+		if (ctdb->do_setsched) {
+			ctdb_restore_scheduler(ctdb);
+		}
 	}
+	return pid;
 }
 
 void set_nonblocking(int fd)
diff --git a/include/ctdb_private.h b/include/ctdb_private.h
index deba46b2..2d9315f6 100644
--- a/include/ctdb_private.h
+++ b/include/ctdb_private.h
@@ -993,6 +993,7 @@ void ctdb_node_connected(struct ctdb_node *node);
 bool ctdb_blocking_freeze(struct ctdb_context *ctdb);
 void ctdb_set_scheduler(struct ctdb_context *ctdb);
 void ctdb_restore_scheduler(struct ctdb_context *ctdb);
+pid_t ctdb_fork(struct ctdb_context *ctdb);
 int32_t ctdb_control_takeover_ip(struct ctdb_context *ctdb, 
 				 struct ctdb_req_control *c,
 				 TDB_DATA indata, 
diff --git a/server/ctdb_lockwait.c b/server/ctdb_lockwait.c
index 48198fd1..1d3a5976 100644
--- a/server/ctdb_lockwait.c
+++ b/server/ctdb_lockwait.c
@@ -117,7 +117,7 @@ struct lockwait_handle *ctdb_lockwait(struct ctdb_db_context *ctdb_db,
 		return NULL;
 	}
 
-	result->child = fork();
+	result->child = ctdb_fork(ctdb_db->ctdb);
 
 	if (result->child == (pid_t)-1) {
 		close(result->fd[0]);
diff --git a/server/ctdb_logging.c b/server/ctdb_logging.c
index 7e5367ea..27b990ef 100644
--- a/server/ctdb_logging.c
+++ b/server/ctdb_logging.c
@@ -96,7 +96,7 @@ int start_syslog_daemon(struct ctdb_context *ctdb)
 		return -1;
 	}
 	
-	ctdb->syslogd_pid = fork();
+	ctdb->syslogd_pid = ctdb_fork(ctdb);
 	if (ctdb->syslogd_pid == (pid_t)-1) {
 		printf("Failed to create syslog child process\n");
 		close(state->fd[0]);
@@ -454,7 +454,7 @@ struct ctdb_log_state *ctdb_fork_with_logging(TALLOC_CTX *mem_ctx,
 		goto free_log;
 	}
 
-	*pid = fork();
+	*pid = ctdb_fork(ctdb);
 
 	/* Child? */
 	if (*pid == 0) {
diff --git a/server/ctdb_monitor.c b/server/ctdb_monitor.c
index 7f5da5c3..fa642fb3 100644
--- a/server/ctdb_monitor.c
+++ b/server/ctdb_monitor.c
@@ -83,7 +83,7 @@ void ctdb_run_notification_script(struct ctdb_context *ctdb, const char *event)
 		return;
 	}
 
-	child = fork();
+	child = ctdb_fork(ctdb);
 	if (child == (pid_t)-1) {
 		DEBUG(DEBUG_ERR,("Failed to fork() a notification child process\n"));
 		return;
diff --git a/server/ctdb_persistent.c b/server/ctdb_persistent.c
index 9346f7d0..f9a20510 100644
--- a/server/ctdb_persistent.c
+++ b/server/ctdb_persistent.c
@@ -524,7 +524,7 @@ struct childwrite_handle *ctdb_childwrite(struct ctdb_db_context *ctdb_db,
 		return NULL;
 	}
 
-	result->child = fork();
+	result->child = ctdb_fork(ctdb_db->ctdb);
 
 	if (result->child == (pid_t)-1) {
 		close(result->fd[0]);
diff --git a/server/ctdb_recoverd.c b/server/ctdb_recoverd.c
index 9caa5024..b2c08ced 100644
--- a/server/ctdb_recoverd.c
+++ b/server/ctdb_recoverd.c
@@ -2768,7 +2768,7 @@ static int check_recovery_lock(struct ctdb_context *ctdb)
 		return -1;
 	}
 
-	state->child = fork();
+	state->child = ctdb_fork(ctdb);
 	if (state->child == (pid_t)-1) {
 		DEBUG(DEBUG_CRIT,(__location__ " fork() failed in check_reclock child\n"));
 		close(state->fd[0]);
diff --git a/server/ctdb_traverse.c b/server/ctdb_traverse.c
index dcb16b22..5ad374f0 100644
--- a/server/ctdb_traverse.c
+++ b/server/ctdb_traverse.c
@@ -153,7 +153,7 @@ static struct ctdb_traverse_local_handle *ctdb_traverse_local(struct ctdb_db_con
 		return NULL;
 	}
 
-	h->child = fork();
+	h->child = ctdb_fork(ctdb_db->ctdb);
 
 	if (h->child == (pid_t)-1) {
 		close(h->fd[0]);
diff --git a/server/ctdb_vacuum.c b/server/ctdb_vacuum.c
index 4104853d..4aac302d 100644
--- a/server/ctdb_vacuum.c
+++ b/server/ctdb_vacuum.c
@@ -836,7 +836,7 @@ ctdb_vacuum_event(struct event_context *ev, struct timed_event *te,
 		return;
 	}
 
-	child_ctx->child_pid = fork();
+	child_ctx->child_pid = ctdb_fork(ctdb);
 	if (child_ctx->child_pid == (pid_t)-1) {
 		close(child_ctx->fd[0]);
 		close(child_ctx->fd[1]);
diff --git a/server/eventscript.c b/server/eventscript.c
index ce2fd89e..9ba3a5d9 100644
--- a/server/eventscript.c
+++ b/server/eventscript.c
@@ -511,9 +511,8 @@ static void debug_timeout(struct ctdb_event_script_state *state)
 	sprintf(buf, "{ pstree -p; cat /proc/locks; ls -li /var/ctdb/ /var/ctdb/persistent; }"
 			" >/tmp/ctdb.event.%s.%d", tbuf, getpid());
 
-	pid = fork();
+	pid = ctdb_fork(state->ctdb);
 	if (pid == 0) {
-		ctdb_reduce_priority(state->ctdb);
 		system(buf);
 		/* Now we can kill the child */
 		kill(state->child, SIGTERM);