* include/threads.h,include/threads_funcs.h: reverted Win32 pthread implementation to the old code. Fixed vlc_cond_broadcast() for WinNT/2K/XP. Additional vlc_cond_* implementations for Win9x. * src/interface/main.c: renamed --fast_pthread option into --fast-mutex. Added a --win9x-cv-method option to choose which vlc_cond_* implementation we want on Win9x.

886080d9 · Gildas Bazin · 1d050f96 · 886080d9 · 886080d9 · 886080d9
Commit 886080d9 authored Jul 29, 2002 by Gildas Bazin
5 changed files
--- a/include/threads.h
+++ b/include/threads.h
@@ -3,7 +3,7 @@
 * This header provides a portable threads implementation.
 *****************************************************************************
 * Copyright (C) 1999, 2000 VideoLAN
- * $Id: threads.h,v 1.42.2.1 2002/06/17 08:37:56 sam Exp $
+ * $Id: threads.h,v 1.42.2.2 2002/07/29 16:12:24 gbazin Exp $
 *
 * Authors: Jean-Marc Dressler <polux@via.ecp.fr>
 *          Samuel Hocevar <sam@via.ecp.fr>
@@ -114,14 +114,12 @@ typedef struct
 typedef struct
 {
-    int                 i_waiting_threads;
+    volatile int        i_waiting_threads;
    /* WinNT/2K/XP implementation */
-    HANDLE              semaphore;
+    HANDLE              event;
-    HANDLE              signal;
-    boolean_t           b_broadcast;
    /* Win95/98/ME implementation */
-    enum                { SIGNAL = 0, BROADCAST = 1 };
+    HANDLE              semaphore;
-    HANDLE              p_events[2];
+    CRITICAL_SECTION    csection;
 } vlc_cond_t;
 typedef unsigned (__stdcall *PTHREAD_START) (void *);

--- a/include/threads_funcs.h
+++ b/include/threads_funcs.h
@@ -3,7 +3,7 @@
 * This header provides a portable threads implementation.
 *****************************************************************************
 * Copyright (C) 1999, 2000 VideoLAN
- * $Id: threads_funcs.h,v 1.4.2.2 2002/07/25 22:23:52 sam Exp $
+ * $Id: threads_funcs.h,v 1.4.2.3 2002/07/29 16:12:24 gbazin Exp $
 *
 * Authors: Jean-Marc Dressler <polux@via.ecp.fr>
 *          Samuel Hocevar <sam@via.ecp.fr>
@@ -97,7 +97,7 @@ static inline int vlc_mutex_init( vlc_mutex_t *p_mutex )
     * function and have a 100% correct vlc_cond_wait() implementation.
     * As this function is not available on Win9x, we can use the faster
     * CriticalSections */
-    if( (GetVersion() < 0x80000000) && !p_main->p_sys->b_fast_pthread )
+    if( p_main->p_sys->SignalObjectAndWait && !p_main->p_sys->b_fast_mutex )
    {
        /* We are running on NT/2K/XP, we can use SignalObjectAndWait */
        p_mutex->mutex = CreateMutex( 0, FALSE, 0 );
@@ -349,24 +349,34 @@ static inline int vlc_cond_init( vlc_cond_t *p_condvar )
    /* Initialize counter */
    p_condvar->i_waiting_threads = 0;
-    if( (GetVersion() < 0x80000000) && !p_main->p_sys->b_fast_pthread )
+    if( p_main->p_sys->i_win9x_cv == 0 )
    {
-        /* Create an auto-reset event and a semaphore. */
+        /* Create an auto-reset event. */
-        p_condvar->signal = CreateEvent( NULL, FALSE, FALSE, NULL );
+        p_condvar->event = CreateEvent( NULL,   /* no security */
-        p_condvar->semaphore = CreateSemaphore( NULL, 0, 0x7fffffff, NULL );
+                                        FALSE,  /* auto-reset event */
+                                        FALSE,  /* start non-signaled */
-        p_condvar->b_broadcast = 0;
+                                        NULL ); /* unnamed */
-        return !p_condvar->signal || !p_condvar->semaphore;
+        p_condvar->semaphore = NULL;
+        return !p_condvar->event;
    }
    else
    {
-        p_condvar->signal = NULL;
+        p_condvar->semaphore = CreateSemaphore( NULL,       /* no security */
+                                                0,          /* initial count */
+                                                0x7fffffff, /* max count */
+                                                NULL );     /* unnamed */
+        if( p_main->p_sys->i_win9x_cv == 1 )
+            /* Create a manual-reset event initially signaled. */
+            p_condvar->event = CreateEvent( NULL, TRUE, TRUE, NULL );
+        else
+            /* Create a auto-reset event. */
+            p_condvar->event = CreateEvent( NULL, FALSE, FALSE, NULL );
+        InitializeCriticalSection( &p_condvar->csection );
-        /* Create an auto-reset event and a manual-reset event. */
+        return !p_condvar->semaphore || !p_condvar->event;
-        p_condvar->p_events[0] = CreateEvent( NULL, FALSE, FALSE, NULL );
-        p_condvar->p_events[1] = CreateEvent( NULL, TRUE, FALSE, NULL );
-        return !p_condvar->p_events[0] || !p_condvar->p_events[1];
    }
 #elif defined( PTHREAD_COND_T_IN_PTHREAD_H )
@@ -414,15 +424,40 @@ static inline int vlc_cond_signal( vlc_cond_t *p_condvar )
    /* Release one waiting thread if one is available. */
    /* For this trick to work properly, the vlc_cond_signal must be surrounded
     * by a mutex. This will prevent another thread from stealing the signal */
-    if( p_condvar->i_waiting_threads )
+    if( !p_condvar->semaphore )
+    {
+        PulseEvent( p_condvar->event );
+    }
+    else if( p_main->p_sys->i_win9x_cv == 1 )
    {
-        if( p_condvar->signal )
+        /* Wait for the gate to be open */
+        WaitForSingleObject( p_condvar->event, INFINITE );
+        if( p_condvar->i_waiting_threads )
        {
+            /* Using a semaphore exposes us to a race condition. It is
+             * possible for another thread to start waiting on the semaphore
+             * just after we signaled it and thus steal the signal.
+             * We have to prevent new threads from entering the cond_wait(). */
+            ResetEvent( p_condvar->event );
+            /* A semaphore is used here because Win9x doesn't have
+             * SignalObjectAndWait() and thus a race condition exists
+             * during the time we release the mutex and the time we start
+             * waiting on the event (more precisely, the signal can sometimes
+             * be missed by the waiting thread if we use PulseEvent()). */
            ReleaseSemaphore( p_condvar->semaphore, 1, 0 );
        }
-        else
+    }
+    else
+    {
+        if( p_condvar->i_waiting_threads )
        {
-            SetEvent( p_condvar->p_events[0] );
+            ReleaseSemaphore( p_condvar->semaphore, 1, 0 );
+            /* Wait for the last thread to be awakened */
+            WaitForSingleObject( p_condvar->event, INFINITE );
        }
    }
    return 0;
@@ -495,23 +530,36 @@ static inline int vlc_cond_broadcast( vlc_cond_t *p_condvar )
 #elif defined( WIN32 )
    /* Release all waiting threads. */
-    if( p_condvar->i_waiting_threads )
+    int i;
+    if( !p_condvar->semaphore )
+        for( i = p_condvar->i_waiting_threads; i > 0; i-- )
+            PulseEvent( p_condvar->event );
+    else if( p_main->p_sys->i_win9x_cv == 1 )
    {
-        if( p_condvar->signal )
+        /* Wait for the gate to be open */
+        WaitForSingleObject( p_condvar->event, INFINITE );
+        if( p_condvar->i_waiting_threads )
        {
-            p_condvar->b_broadcast = 1;
+            /* close gate */
-            /* This call is atomic */
+            ResetEvent( p_condvar->event );
            ReleaseSemaphore( p_condvar->semaphore,
                              p_condvar->i_waiting_threads, 0 );
-            /* Wait for all threads to get the semaphore */
-            WaitForSingleObject( p_condvar->signal, INFINITE );
-            p_condvar->b_broadcast = 0;
        }
-        else
+    }
+    else
+    {
+        if( p_condvar->i_waiting_threads )
        {
-            SetEvent( p_condvar->p_events[1] );
+            ReleaseSemaphore( p_condvar->semaphore,
+                              p_condvar->i_waiting_threads, 0 );
+            /* Wait for the last thread to be awakened */
+            WaitForSingleObject( p_condvar->event, INFINITE );
        }
    }
    return 0;
 #elif defined( PTHREAD_COND_T_IN_PTHREAD_H )
@@ -592,58 +640,76 @@ static inline int _vlc_cond_wait( char * psz_file, int i_line,
    return i_ret;
 #elif defined( WIN32 )
-    /* Increase our wait count */
+    if( !p_condvar->semaphore )
-    p_condvar->i_waiting_threads++;
-    if( p_condvar->signal )
    {
+        /* Increase our wait count */
+        p_condvar->i_waiting_threads++;
+        if( p_main->p_sys->SignalObjectAndWait )
        /* It is only possible to atomically release the mutex and initiate the
         * waiting on WinNT/2K/XP. Win9x doesn't have SignalObjectAndWait(). */
-        p_main->p_sys->SignalObjectAndWait( p_mutex->mutex,
+            p_main->p_sys->SignalObjectAndWait( p_mutex->mutex,
-                                            p_condvar->semaphore,
+                                                p_condvar->event,
-                                            INFINITE, FALSE );
-        /* XXX: we should protect i_waiting_threads with a mutex, but
-         * is it really worth it ? */
-        p_condvar->i_waiting_threads--;
-        if( p_condvar->b_broadcast
-             && p_condvar->i_waiting_threads == 0 )
-        {
-            p_main->p_sys->SignalObjectAndWait( p_condvar->signal,
-                                                p_mutex->mutex,
                                                INFINITE, FALSE );
-        }
        else
        {
-            /* Just take back the lock */
+            LeaveCriticalSection( &p_mutex->csection );
-            WaitForSingleObject( p_mutex->mutex, INFINITE );
+            WaitForSingleObject( p_condvar->event, INFINITE );
        }
-        return 0;
+    }
+    else if( p_main->p_sys->i_win9x_cv == 1 )
+    {
+        int i_waiting_threads;
+        /* Wait for the gate to be open */
+        WaitForSingleObject( p_condvar->event, INFINITE );
+        /* Increase our wait count */
+        p_condvar->i_waiting_threads++;
+        LeaveCriticalSection( &p_mutex->csection );
+        WaitForSingleObject( p_condvar->semaphore, INFINITE );
+        /* Decrement and test must be atomic */
+        EnterCriticalSection( &p_condvar->csection );
+        /* Decrease our wait count */
+        i_waiting_threads = --p_condvar->i_waiting_threads;
+        LeaveCriticalSection( &p_condvar->csection );
+        /* Reopen the gate if we were the last waiting thread */
+        if( !i_waiting_threads )
+            SetEvent( p_condvar->event );
    }
    else
    {
-        int i_ret;
+        int i_waiting_threads;
+        /* Increase our wait count */
+        p_condvar->i_waiting_threads++;
-        /* Release the mutex, wait, and reacquire. */
        LeaveCriticalSection( &p_mutex->csection );
-        i_ret = WaitForMultipleObjects( 2, p_condvar->p_events,
+        WaitForSingleObject( p_condvar->semaphore, INFINITE );
-                                        FALSE, INFINITE );
-        EnterCriticalSection( &p_mutex->csection );
+        /* Decrement and test must be atomic */
+        EnterCriticalSection( &p_condvar->csection );
        /* Decrease our wait count */
-        p_condvar->i_waiting_threads--;
+        i_waiting_threads = --p_condvar->i_waiting_threads;
-        /* If we are the last waiter and it was a broadcast signal, reset
+        LeaveCriticalSection( &p_condvar->csection );
-         * the broadcast event. */
-        if( i_ret == WAIT_OBJECT_0 + 1
+        /* Signal that the last waiting thread just went through */
-             && p_condvar->i_waiting_threads == 0 )
+        if( !i_waiting_threads )
-        {
+            SetEvent( p_condvar->event );
-            ResetEvent( p_condvar->p_events[1] );
-        } 
-        return( i_ret == WAIT_FAILED );
    }
+    /* Reacquire the mutex before returning. */
+    vlc_mutex_lock( p_mutex );
+    return 0;
 #elif defined( PTHREAD_COND_T_IN_PTHREAD_H )
 #ifndef DEBUG
@@ -733,16 +799,11 @@ static inline int _vlc_cond_destroy( char * psz_file, int i_line,
    return st_cond_destroy( *p_condvar );
 #elif defined( WIN32 )
-    if( p_condvar->signal )
+    if( !p_condvar->semaphore )
-    {
+        return !CloseHandle( p_condvar->event );
-        return !CloseHandle( p_condvar->signal )
-                 || !CloseHandle( p_condvar->semaphore );
-    }
    else
-    {
+        return !CloseHandle( p_condvar->event )
-        return !CloseHandle( p_condvar->p_events[0] )
+          || !CloseHandle( p_condvar->semaphore );
-                 || !CloseHandle( p_condvar->p_events[1] );
-    }
 #elif defined( PTHREAD_COND_T_IN_PTHREAD_H )
    int i_result = pthread_cond_destroy( p_condvar );

--- a/include/win32_specific.h
+++ b/include/win32_specific.h
@@ -2,7 +2,7 @@
 * win32_specific.h: Win32 specific features 
 *****************************************************************************
 * Copyright (C) 2001 VideoLAN
- * $Id: win32_specific.h,v 1.2 2002/04/02 23:43:57 gbazin Exp $
+ * $Id: win32_specific.h,v 1.2.2.1 2002/07/29 16:12:24 gbazin Exp $
 *
 * Authors: Samuel Hocevar <sam@zoy.org>
 *          Gildas Bazin <gbazin@netcourrier.com>
@@ -36,6 +36,7 @@ typedef BOOL (WINAPI *SIGNALOBJECTANDWAIT)( HANDLE, HANDLE, DWORD, BOOL );
 typedef struct main_sys_s
 {
    SIGNALOBJECTANDWAIT SignalObjectAndWait;
-    boolean_t b_fast_pthread;
+    boolean_t b_fast_mutex;
+    int i_win9x_cv;
 } main_sys_t;
--- a/src/interface/main.c
+++ b/src/interface/main.c
@@ -4,7 +4,7 @@
 * and spawn threads.
 *****************************************************************************
 * Copyright (C) 1998-2001 VideoLAN
- * $Id: main.c,v 1.195.2.4 2002/07/19 21:14:40 massiot Exp $
+ * $Id: main.c,v 1.195.2.5 2002/07/29 16:12:24 gbazin Exp $
 *
 * Authors: Vincent Seguin <seguin@via.ecp.fr>
 *          Samuel Hocevar <sam@zoy.org>
@@ -337,11 +337,23 @@
 #define DEMUX_LONGTEXT N_( \
    "This is a legacy entry to let you configure demux modules")
-#define FAST_PTHREAD_TEXT N_("fast pthread on NT/2K/XP (developpers only)")
+#define FAST_MUTEX_TEXT N_("fast mutex on NT/2K/XP (developpers only)")
-#define FAST_PTHREAD_LONGTEXT N_( \
+#define FAST_MUTEX_LONGTEXT N_( \
-    "On Windows NT/2K/XP we use a slow but correct pthread implementation, " \
+    "On Windows NT/2K/XP we use a slow mutex implementation but which " \
-    "you can also use this faster implementation but you might experience " \
+    "allows us to correctely implement condition variables. " \
-    "problems with it.")
+    "You can also use the faster Win9x implementation but you might " \
+    "experience problems with it.")
+#define WIN9X_CV_TEXT N_("Condition variables implementation for Win9x " \
+    "(developpers only)")
+#define WIN9X_CV_LONGTEXT N_( \
+    "On Windows 9x/Me we use a fast but not correct condition variables " \
+    "implementation (more precisely there is a possibility for a race " \
+    "condition to happen). " \
+    "However it is possible to use slower alternatives which should be more " \
+    "robust. " \
+    "Currently you can choose between implementation 0 (which is the " \
+    "default and the fastest), 1 and 2.")
 /*
 * Quick usage guide for the configuration options:
@@ -436,7 +448,8 @@ ADD_MODULE  ( "access", MODULE_CAPABILITY_ACCESS, NULL, NULL, ACCESS_TEXT, ACCES
 ADD_MODULE  ( "demux", MODULE_CAPABILITY_DEMUX, NULL, NULL, DEMUX_TEXT, DEMUX_LONGTEXT )
 #if defined(WIN32)
-ADD_BOOL ( "fast_pthread", 0, NULL, FAST_PTHREAD_TEXT, FAST_PTHREAD_LONGTEXT )
+ADD_BOOL ( "fast-mutex", 0, NULL, FAST_MUTEX_TEXT, FAST_MUTEX_LONGTEXT )
+ADD_INTEGER ( "win9x-cv-method", 0, NULL, WIN9X_CV_TEXT, WIN9X_CV_LONGTEXT )
 #endif
 MODULE_CONFIG_STOP

--- a/src/misc/win32_specific.c
+++ b/src/misc/win32_specific.c
@@ -2,7 +2,7 @@
 * win32_specific.c: Win32 specific features 
 *****************************************************************************
 * Copyright (C) 2001 VideoLAN
- * $Id: win32_specific.c,v 1.7 2002/04/27 22:11:22 gbazin Exp $
+ * $Id: win32_specific.c,v 1.7.2.1 2002/07/29 16:12:24 gbazin Exp $
 *
 * Authors: Samuel Hocevar <sam@zoy.org>
 *          Gildas Bazin <gbazin@netcourrier.com>
@@ -49,9 +49,16 @@ void system_Init( int *pi_argc, char *ppsz_argv[], char *ppsz_env[] )
    }
    /* dynamically get the address of SignalObjectAndWait */
-    hInstLib = LoadLibrary( "kernel32" );
+    if( (GetVersion() < 0x80000000) )
-    p_main->p_sys->SignalObjectAndWait =
+    {
-        (SIGNALOBJECTANDWAIT)GetProcAddress( hInstLib, "SignalObjectAndWait" );
+        /* We are running on NT/2K/XP, we can use SignalObjectAndWait */
+        hInstLib = LoadLibrary( "kernel32" );
+        if( hInstLib)
+            p_main->p_sys->SignalObjectAndWait =
+                (SIGNALOBJECTANDWAIT)GetProcAddress( hInstLib,
+                                                     "SignalObjectAndWait" );
+    }
+    else p_main->p_sys->SignalObjectAndWait = NULL;
    /* WinSock Library Init. */
    i_err = WSAStartup( MAKEWORD( 1, 1 ), &Data );
@@ -69,7 +76,8 @@ void system_Init( int *pi_argc, char *ppsz_argv[], char *ppsz_env[] )
 *****************************************************************************/
 void system_Configure( void )
 {
-    p_main->p_sys->b_fast_pthread = config_GetIntVariable( "fast_pthread" );
+    p_main->p_sys->b_fast_mutex = config_GetIntVariable( "fast-mutex" );
+    p_main->p_sys->i_win9x_cv = config_GetIntVariable( "win9x-cv-method" );
 }
 /*****************************************************************************