* Lock citadel.control using flock() immediately after

[citadel.git] / citadel / control.c

diff --git a/citadel/control.c b/citadel/control.c
index f2268d8fa2f06c655e71ea313675a8992d2c5efa..0c9dd11b13b8f815fe2b1932d7168712cd5df526 100644 (file)
--- a/citadel/control.c
+++ b/citadel/control.c
@@ -28,6 +28,7 @@
 #include <errno.h>
 #include <limits.h>
 #include <sys/types.h>
+#include <sys/file.h>
 #include "citadel.h"
 #include "server.h"
 #include "control.h"
@@ -48,12 +49,27 @@ struct CitControl CitControl;
 extern struct config config;
 FILE *control_fp = NULL;
 
+
+
+/*
+ * lock_control  -  acquire a lock on the control record file.
+ *                  This keeps multiple citservers from running concurrently.
+ */
+void lock_control(void)
+{
+       if (flock(fileno(control_fp), (LOCK_EX | LOCK_NB))) {
+               lprintf(CTDL_EMERG, "citserver: unable to lock %s.\n", file_citadel_control);
+               lprintf(CTDL_EMERG, "Is another citserver already running?\n");
+               exit(1);
+       }
+}
+
+
 /*
  * get_control  -  read the control record into memory.
  */
 void get_control(void)
 {
-
        /* Zero it out.  If the control record on disk is missing or short,
         * the system functions with all control record fields initialized
         * to zero.
@@ -62,12 +78,14 @@ void get_control(void)
        if (control_fp == NULL) {
                control_fp = fopen(file_citadel_control, "rb+");
                if (control_fp != NULL) {
+                       lock_control();
                        fchown(fileno(control_fp), config.c_ctdluid, -1);
                }
        }
        if (control_fp == NULL) {
                control_fp = fopen(file_citadel_control, "wb+");
                if (control_fp != NULL) {
+                       lock_control();
                        fchown(fileno(control_fp), config.c_ctdluid, -1);
                        memset(&CitControl, 0, sizeof(struct CitControl));
                        fwrite(&CitControl, sizeof(struct CitControl),