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user32: Leave critical section before calling callbacks in EnumDisplayMonitors(). 

Previously, callbacks were called with a critical section held. It was
intended that monitor handles passed to callbacks should always be valid.
But it created a deadlock condition when callbacks call other functions
which try to grab the critical section using a different thread. Tests
also show that a monitor handle can be invalid after a display change.
So do not hold the critical section when calling callbacks. Monitor
handles will be checked when passed to GetMonitorInfo(), which is the
sole function that consumes HMONITORs.

Signed-off-by: Zhiyi Zhang <zzhang@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>
This commit is contained in:
Zhiyi Zhang 2020-05-05 20:30:39 +08:00 committed by Alexandre Julliard
parent 065690be32
commit 449ca2fbf9
1 changed files with 15 additions and 9 deletions
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24
dlls/user32/sysparams.c
View File

@ -4126,28 +4126,34 @@ static BOOL CALLBACK enum_mon_callback( HMONITOR monitor, HDC hdc, LPRECT rect,
BOOL CDECL nulldrv_EnumDisplayMonitors( HDC hdc, RECT *rect, MONITORENUMPROC proc, LPARAM lp )
{
RECT default_rect = {0, 0, 640, 480};
DWORD i;
RECT monitor_rect;
DWORD i = 0;
TRACE("(%p, %p, %p, 0x%lx)\n", hdc, rect, proc, lp);
if (update_monitor_cache())
{
EnterCriticalSection( &monitors_section );
for (i = 0; i < monitor_count; i++)
while (TRUE)
{
if (!proc( (HMONITOR)(UINT_PTR)(i + 1), hdc, &monitors[i].rcMonitor, lp ))
EnterCriticalSection( &monitors_section );
if (i >= monitor_count)
{
LeaveCriticalSection( &monitors_section );
return FALSE;
return TRUE;
}
monitor_rect = monitors[i].rcMonitor;
LeaveCriticalSection( &monitors_section );
if (!proc( (HMONITOR)(UINT_PTR)(i + 1), hdc, &monitor_rect, lp ))
return FALSE;
++i;
}
LeaveCriticalSection( &monitors_section );
return TRUE;
}
/* Fallback to report one monitor if using SetupAPI failed */
if (!proc( NULLDRV_DEFAULT_HMONITOR, hdc, &default_rect, lp ))
SetRect( &monitor_rect, 0, 0, 640, 480 );
if (!proc( NULLDRV_DEFAULT_HMONITOR, hdc, &monitor_rect, lp ))
return FALSE;
return TRUE;
}