Michael Schnell wrote:
On 10/21/2015 02:42 PM, Michael Schnell wrote:
CheckSynchronize()
Unfortunately there is no decent documentation on CheckSynchronize().
So in very short (and just hopefully correct):
CheckSynchronize() needs to be called by the main thread (in fact a
threat becomes the main thread _because_ it calls CheckSynchronize().
The Events thrown by other Threads via TThread.Synchronize and
TThread.Queue are executed as sub-procedures of CheckSynchronize() and
hence they are executed in the main thread and they are executed in the
order they have been queued by other threads.
It is a very bad idea to do a closed loop such as
while (TRUE) CheckSynchronize();
As this will use 100 % CPU time and hence will reduce the performance of
all other threads (and every application that is running on the processor).
That is why CheckSynchronize() provides using the parameter "Timeout",
that defines how long to wait until returning in case no event is
queued. (0 or no parameter => return immediately)
AFAIR if an Event is in the queue same is executed and
CheckSynchronize(I) returns without checking if more Events are queued.
AFAIK the return parameter of CheckSynchronize() does not give any
decent result and needs to be ignored.
Seems reasonable. I think I've used it in one place, which is a console
program which spends most of its time waiting for keyboard input but
also has
procedure MainThreadYield;
begin
Assert(InterlockedExchange(mainThreadYieldEntryCounter, 1) = 0,
'MainThreadYield reentered');
{$ifndef LCL }
CheckSynchronize;
{$endif LCL }
Assert(InterlockedExchange(mainThreadYieldEntryCounter, 0) = 1,
'MainThreadYield reexited')
end { MainThreadYield } ;
I don't know whether I've overlooked anything significant there, but it
appears robust and activity triggered by around half a dozen background
threads appears as expected.
--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk
[Opinions above are the author's, not those of his employers or colleagues]
--
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