create /.lock file to protect sharing config directory

Makefile

@@ -153,7 +153,8 @@ SRCS =  src/version.c \
 	src/esfilter.c \
 	src/intlconv.c \
 	src/profile.c \
-	src/bouquet.c
+	src/bouquet.c \
+	src/lock.c
 
 SRCS-${CONFIG_UPNP} += \
 	src/upnp.c

src/config.c

@@ -25,12 +25,15 @@
 #include "uuid.h"
 #include "htsbuf.h"
 #include "spawn.h"
+#include "lock.h"
 
 /* *************************************************************************
  * Global data
  * ************************************************************************/
 
 static htsmsg_t *config;
+static char config_lock[PATH_MAX];
+static int config_lock_fd;
 
 /* *************************************************************************
  * Config migration
@@ -1329,6 +1332,11 @@ config_init ( const char *path, int backup )
   /* Configure settings routines */
   hts_settings_init(path);
 
+  /* Lock it */
+  hts_settings_buildpath(config_lock, sizeof(config_lock), ".lock");
+  if ((config_lock_fd = file_lock(config_lock, 3)) < 0)
+    exit(78); /* config error */
+
   /* Load global settings */
   config = hts_settings_load("config");
   if (!config) {
@@ -1351,7 +1359,9 @@ config_init ( const char *path, int backup )
 
 void config_done ( void )
 {
+  /* note: tvhlog is inactive !!! */
   htsmsg_destroy(config);
+  file_unlock(config_lock, config_lock_fd);
 }
 
 void config_save ( void )

src/lock.c

@@ -0,0 +1,128 @@
+/*
+ * Copyright (c) 2014 Jaroslav Kysela <perex@perex.cz>
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/file.h>
+
+#include "tvheadend.h"
+#include "lock.h"
+
+static
+int state_lock_(const char *lfile, int lock, int timeout, int _fd)
+{
+    int fd = -1, err = 0;
+    struct flock lck;
+    struct stat st;
+    char lcktxt[12];
+
+    lck.l_type = lock ? F_WRLCK : F_UNLCK;
+    lck.l_whence = SEEK_SET;
+    lck.l_start = 0;
+    lck.l_len = 11;
+    lck.l_pid = 0;
+    if (lock) {
+        snprintf(lcktxt, sizeof(lcktxt), "%10li\n", (long)getpid());
+    } else {
+        snprintf(lcktxt, sizeof(lcktxt), "%10s\n", "");
+        fd = _fd;
+    }
+    while (fd < 0 && timeout-- > 0) {
+       fd = open(lfile, O_RDWR);
+       if (!lock && fd < 0) {
+           err = -EIO;
+           goto out;
+       }
+       if (fd < 0) {
+           fd = open(lfile, O_RDWR|O_CREAT|O_EXCL, 0644);
+           if (fd < 0) {
+               if (errno == EBUSY || errno == EAGAIN) {
+                   sleep(1);
+                   timeout--;
+               } else {
+                   err = -errno;
+                   goto out;
+               }
+           }
+       }
+    }
+    if (fd < 0 && timeout <= 0) {
+       err = -EBUSY;
+       goto out;
+    }
+    if (fstat(fd, &st) < 0) {
+       err = -errno;
+       goto out;
+    }
+    if (st.st_size != 11 || !lock) {
+        if (write(fd, lcktxt, 11) != 11) {
+            err = -EIO;
+            goto out;
+        }
+        if (lock && lseek(fd, 0, SEEK_SET)) {
+            err = -errno;
+            goto out;
+        }
+    }
+    while (timeout > 0) {
+        if (fcntl(fd, F_SETLK, &lck) < 0) {
+            sleep(1);
+            timeout--;
+        } else {
+            break;
+        }
+    }
+    if (timeout <= 0) {
+        err = -EBUSY;
+        goto out;
+    }
+    if (lock) {
+        if (write(fd, lcktxt, 11) != 11) {
+	    err = -EIO;
+            goto out;
+        }
+        return fd;
+    }
+    err = 0;
+
+out:
+    if (fd >= 0)
+        close(fd);
+    return err;
+}
+
+int file_lock(const char *lfile, int timeout)
+{
+    int err;
+
+    err = state_lock_(lfile, 1, timeout, -1);
+    if (err < 0)
+        tvherror("lock", "file %s lock error: %s", lfile, strerror(-err));
+    return err;
+}
+
+int file_unlock(const char *lfile, int _fd)
+{
+    int err;
+
+    err = state_lock_(lfile, 0, 10, _fd);
+    if (err < 0)
+        tvherror("lock", "file %s unlock error: %s", lfile, strerror(-err));
+    return err;
+}

src/lock.h

@@ -0,0 +1,25 @@
+/*
+ *  File locking
+ *  Copyright (C) 2014 Jaroslav Kysela
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef TVH_LOCK_H
+#define TVH_LOCK_H
+
+int file_lock(const char *lfile, int timeout);
+int file_unlock(const char *lfile, int _fd);
+
+#endif /* TVH_LOCK_H */

src/main.c

@@ -939,7 +939,6 @@ main(int argc, char **argv)
   tvhftrace("main", imagecache_done);
   tvhftrace("main", lang_code_done);
   tvhftrace("main", api_done);
-  tvhftrace("main", config_done);
   tvhftrace("main", hts_settings_done);
   tvhftrace("main", dvb_done);
   tvhftrace("main", lang_str_done);
@@ -953,6 +952,8 @@ main(int argc, char **argv)
   tvhlog(LOG_NOTICE, "STOP", "Exiting HTS Tvheadend");
   tvhlog_end();
 
+  tvhftrace("main", config_done);
+
   if(opt_fork)
     unlink(opt_pidpath);