From 805e51eff86a1c249d80728dcd3f8d70313bc35e Mon Sep 17 00:00:00 2001
From: Kornel Benko <kornel@lyx.org>
Date: Wed, 20 Nov 2013 19:40:32 +0100
Subject: [PATCH] Implement file locking and apply to configure

Functions for file locking are added. They are used for ensuring that
for specified userdir only one LyX process runs configure.
---
 configure.ac                            |  2 +-
 development/cmake/ConfigureChecks.cmake |  2 +-
 src/LyX.cpp                             | 11 +++++++++--
 src/support/filetools.cpp               | 22 ++++++++++++++++++++++
 src/support/filetools.h                 |  2 ++
 5 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/configure.ac b/configure.ac
index b572f4980c..1fe6d9d691 100644
--- a/configure.ac
+++ b/configure.ac
@@ -174,7 +174,7 @@ fi
 
 LYX_CHECK_DEF(PATH_MAX, limits.h, [int n = PATH_MAX;])
 
-AC_CHECK_FUNCS(chmod close _close fork getpid _getpid lstat mkfifo open _open pclose _pclose popen _popen readlink putenv setenv strerror unsetenv)
+AC_CHECK_FUNCS(chmod close _close fork getpid _getpid lockf lstat mkfifo open _open pclose _pclose popen _popen readlink putenv setenv strerror unsetenv)
 # Check the form of mkdir()
 AC_FUNC_MKDIR
 AC_FUNC_SELECT_ARGTYPES
diff --git a/development/cmake/ConfigureChecks.cmake b/development/cmake/ConfigureChecks.cmake
index b6b0b1476b..71291a53a5 100644
--- a/development/cmake/ConfigureChecks.cmake
+++ b/development/cmake/ConfigureChecks.cmake
@@ -40,7 +40,7 @@ configure_file(${TOP_BINARY_DIR}/configIncludes.h.cmake ${TOP_BINARY_DIR}/config
 set(Function_Defines)
 foreach(_f alloca __argz_count __argz_next __argz_stringify
 	chmod close _close dcgettext fcntl fork __fsetlocking
-	getcwd getegid getgid getpid _getpid gettext getuid lstat mempcpy mkdir _mkdir
+	getcwd getegid getgid getpid _getpid gettext getuid lstat lockf mempcpy mkdir _mkdir
 	mkfifo open _open pclose _pclose popen _popen putenv readlink
 	setenv setlocale strcasecmp stpcpy strdup strerror strtoul tsearch unsetenv wcslen)
   string(TOUPPER ${_f} _UF)
diff --git a/src/LyX.cpp b/src/LyX.cpp
index 09fcfd5398..b777e55f4e 100644
--- a/src/LyX.cpp
+++ b/src/LyX.cpp
@@ -754,8 +754,15 @@ bool LyX::init()
 		prependEnvPath("PATH", replaceEnvironmentPath(lyxrc.path_prefix));
 
 	// Check that user LyX directory is ok.
-	if (queryUserLyXDir(package().explicit_user_support()))
-		reconfigureUserLyXDir();
+	{
+		string const lock_file = package().user_support().absFileName() + ".lyx_configure_lock";
+		int fd = fileLock(lock_file.c_str());
+
+		if (queryUserLyXDir(package().explicit_user_support())) {
+			reconfigureUserLyXDir();
+		}
+		fileUnlock(fd, lock_file.c_str());
+	}
 
 	if (!use_gui) {
 		// No need for a splash when there is no GUI
diff --git a/src/support/filetools.cpp b/src/support/filetools.cpp
index f991455a27..387045f974 100644
--- a/src/support/filetools.cpp
+++ b/src/support/filetools.cpp
@@ -1064,6 +1064,28 @@ bool prefs2prefs(FileName const & filename, FileName const & tempfile, bool lfun
 	return true;
 }
 
+int fileLock(const char * lock_file)
+{
+	int fd = -1;
+#if defined(HAVE_LOCKF)
+	fd = open(lock_file, O_CREAT|O_APPEND|O_SYNC|O_RDWR, 0666);
+	if (lockf(fd, F_LOCK, 0) != 0) {
+		close(fd);
+		return(-1);
+	}
+#endif
+	return(fd);
+}
+
+void fileUnlock(int fd, const char * lock_file)
+{
+#if defined(HAVE_LOCKF)
+	if ( fd >= 0) {
+		(void) lockf(fd, F_ULOCK, 0);
+		close(fd);
+	}
+#endif
+}
 
 } //namespace support
 } // namespace lyx
diff --git a/src/support/filetools.h b/src/support/filetools.h
index 92c6eb57e7..58d11542d4 100644
--- a/src/support/filetools.h
+++ b/src/support/filetools.h
@@ -292,6 +292,8 @@ typedef std::pair<int, std::string> cmd_ret;
 
 cmd_ret const runCommand(std::string const & cmd);
 
+int fileLock(const char * lock_file);
+void fileUnlock(int fd, const char * lock_file);
 
 } // namespace support
 } // namespace lyx