Commit 17a23d08 authored by Simon McVittie's avatar Simon McVittie

dbus_threads_init_default, dbus_threads_init: be safe to call at any time

On Unix, we use a pthreads mutex, which can be allocated and
initialized in global memory.

On Windows, we use a CRITICAL_SECTION, together with a call to
InitializeCriticalSection() from the constructor of a global static
C++ object (thanks to Ralf Habacker for suggesting this approach).

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=54972Signed-off-by: default avatarSimon McVittie <simon.mcvittie@collabora.co.uk>
Reviewed-by: default avatarAlban Crequy <alban.crequy@collabora.co.uk>
Reviewed-by: Ralf Habacker's avatarRalf Habacker <ralf.habacker@freenet.de>
parent 863c989b
......@@ -186,6 +186,7 @@ set (DBUS_UTIL_HEADERS
if (WIN32)
set (DBUS_SHARED_SOURCES ${DBUS_SHARED_SOURCES}
${DBUS_DIR}/dbus-file-win.c
${DBUS_DIR}/dbus-init-win.cpp
${DBUS_DIR}/dbus-sysdeps-win.c
${DBUS_DIR}/dbus-pipe-win.c
${DBUS_DIR}/dbus-sysdeps-thread-win.c
......
......@@ -72,6 +72,7 @@ endif
DBUS_SHARED_arch_sources = \
$(wince_source) \
dbus-file-win.c \
dbus-init-win.cpp \
dbus-pipe-win.c \
dbus-sockets-win.h \
dbus-sysdeps-win.c \
......
/*
* dbus-init-win.cpp - once-per-process initialization
*
* Copyright © 2013 Intel Corporation
*
* Licensed under the Academic Free License version 2.1
*
* 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 2 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, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
*/
#include <config.h>
extern "C"
{
#include "dbus-sysdeps-win.h"
}
class DBusInternalInit
{
public:
DBusInternalInit ()
{
_dbus_threads_windows_init_global ();
}
void must_not_be_omitted ()
{
}
};
static DBusInternalInit init;
extern "C" void
_dbus_threads_windows_ensure_ctor_linked ()
{
/* Do nothing significant, just ensure that the global initializer gets
* linked in. */
init.must_not_be_omitted ();
}
......@@ -26,6 +26,7 @@
#include "dbus-internals.h"
#include "dbus-sysdeps.h"
#include "dbus-list.h"
#include "dbus-threads.h"
#include <stdlib.h>
/**
......@@ -890,7 +891,13 @@ dbus_shutdown (void)
dbus_free (c);
}
/* We wrap this in the thread-initialization lock because
* dbus_threads_init() uses the current generation to tell whether
* we're initialized, so we need to make sure that un-initializing
* propagates into all threads. */
_dbus_threads_lock_platform_specific ();
_dbus_current_generation += 1;
_dbus_threads_unlock_platform_specific ();
}
/** @} */ /** End of public API docs block */
......
......@@ -286,3 +286,17 @@ _dbus_threads_init_platform_specific (void)
return TRUE;
}
static pthread_mutex_t init_mutex = PTHREAD_MUTEX_INITIALIZER;
void
_dbus_threads_lock_platform_specific (void)
{
pthread_mutex_lock (&init_mutex);
}
void
_dbus_threads_unlock_platform_specific (void)
{
pthread_mutex_unlock (&init_mutex);
}
......@@ -30,6 +30,21 @@
#include <windows.h>
static dbus_bool_t global_init_done = FALSE;
static CRITICAL_SECTION init_lock;
/* Called from C++ code in dbus-init-win.cpp. */
void
_dbus_threads_windows_init_global (void)
{
/* this ensures that the object that acts as our global constructor
* actually gets linked in when we're linked statically */
_dbus_threads_windows_ensure_ctor_linked ();
InitializeCriticalSection (&init_lock);
global_init_done = TRUE;
}
struct DBusCondVar {
DBusList *list; /**< list thread-local-stored events waiting on the cond variable */
CRITICAL_SECTION lock; /**< lock protecting the list */
......@@ -272,3 +287,16 @@ _dbus_threads_init_platform_specific (void)
return TRUE;
}
void
_dbus_threads_lock_platform_specific (void)
{
_dbus_assert (global_init_done);
EnterCriticalSection (&init_lock);
}
void
_dbus_threads_unlock_platform_specific (void)
{
_dbus_assert (global_init_done);
LeaveCriticalSection (&init_lock);
}
......@@ -85,6 +85,9 @@ dbus_bool_t _dbus_get_config_file_name(DBusString *config_file,
dbus_bool_t _dbus_get_install_root(char *prefix, int len);
void _dbus_threads_windows_init_global (void);
void _dbus_threads_windows_ensure_ctor_linked (void);
#endif
/** @} end of sysdeps-win.h */
......@@ -520,6 +520,18 @@ dbus_bool_t _dbus_read_local_machine_uuid (DBusGUID *machine_id,
*/
dbus_bool_t _dbus_threads_init_platform_specific (void);
/**
* Lock a static mutex used to protect _dbus_threads_init_platform_specific().
*
* On Windows, this is currently unimplemented and does nothing.
*/
void _dbus_threads_lock_platform_specific (void);
/**
* Undo _dbus_threads_lock_platform_specific().
*/
void _dbus_threads_unlock_platform_specific (void);
dbus_bool_t _dbus_split_paths_and_append (DBusString *dirs,
const char *suffix,
DBusList **dir_list);
......
......@@ -581,15 +581,24 @@ init_locks (void)
dbus_bool_t
dbus_threads_init (const DBusThreadFunctions *functions)
{
_dbus_threads_lock_platform_specific ();
if (thread_init_generation == _dbus_current_generation)
return TRUE;
{
_dbus_threads_unlock_platform_specific ();
return TRUE;
}
if (!_dbus_threads_init_platform_specific() ||
!init_locks ())
return FALSE;
{
_dbus_threads_unlock_platform_specific ();
return FALSE;
}
thread_init_generation = _dbus_current_generation;
_dbus_threads_unlock_platform_specific ();
return TRUE;
}
......@@ -600,11 +609,16 @@ dbus_threads_init (const DBusThreadFunctions *functions)
/**
* Initializes threads. If this function is not called, the D-Bus
* library will not lock any data structures. If it is called, D-Bus
* will do locking, at some cost in efficiency. Note that this
* function must be called BEFORE the second thread is started.
* will do locking, at some cost in efficiency.
*
* Since D-Bus 1.7 it is safe to call this function from any thread,
* any number of times (but it must be called before any other
* libdbus API is used).
*
* It's safe to call dbus_threads_init_default() as many times as you
* want, but only the first time will have an effect.
* In D-Bus 1.6 or older, this function must be called in the main thread
* before any other thread starts. As a result, it is not sufficient to
* call this function in a library or plugin, unless the library or plugin
* imposes a similar requirement on its callers.
*
* dbus_shutdown() reverses the effects of this function when it
* resets all global state in libdbus.
......
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