Re: Inter-process sync question?

"Alex Blekhman" <>
Tue, 21 Jul 2009 15:03:59 +0300
"Vincent Fatica" wrote:

INJECT.EXE creates a named, unsignaled event.

INJECT.EXE creates the remote thread and waits for this thread.

The remote thread loads MYDLL and returns, while MYDLL's DllMain
creates a thread which waits for the event.

The remote thread having ended, INJECT.EXE signals the event
(and closes its handle).

The wait satisfied (event signaled), the thread started by
DllMain continues (and closes its event handle).

It seems to work. Is it sound? Is there a better way?

I think there is a race condition. Here's how I understand your
design (each column is a thread), in pseudocode:

E = CreateEvent()
CreateThread() ------> Thread #1
                      CreateTread() ------> Thread #2
WaitFor(Thread #1) <- return ---------
Signal(E) [race condition starts here] Open(E)
Close(E) WaitFor(E)

As you can see, the INJECT thread signals and closes event E,
while Thread #2 may be still busy and not at the Open(E) call yet.


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