Re: CloseHandle and WriteFile
The issue is more complex. Even for non-overlapped handle, it's not
recommended to use a handle in one thread and close it in another because of
possible race condition between CloseHandle (IRP_MJ_CLEANUP) and
ObReferenceObjectByHandle.
A handle-based file request starts with ObReferenceObjectByHandle. It can
happen that WriteFile gets a valid reference to the file object before
CloseHandle does, but IRP_MJ_CLEANUP will be sent before IRP_MJ_WRITE, which
kind of reverses proper order. If WRITE can wait for indefinite time, it
will stay there, not canceled by CLEANUP. Only TerminateProcess or
TerminateThread will cancel that operation.
"Carl Daniel [VC++ MVP]" <cpdaniel_remove_this_and_nospam@mvps.org.nospam>
wrote in message news:%23G0PpPUyHHA.1164@TK2MSFTNGP02.phx.gbl...
hangaround wrote:
Hi there!
I create a file using CreateFile(...), and write some data to the
file handle ,say hFile, using WriteFile(...) I wonder if I call
CloseHandle (hFile) to the handle, at the same time , WriteFile is
operating on the file handle , whether the WriteFile will block the
CloseHandle?
I would expect that if you called CloseHandle while WriteFile is running
that the write will in fact succeed, possibly without actually "blocking"
the call to CloseHandle. This is because under the covers, a handle is
nothing more than a reference count to a kernel object. Closing the
handle decreases the reference count, but the running call to WriteFile
will have internally referenced the file as well, thus keeping it open for
the duration of the call.
That's just supposition - strictly speaking, it's probably undefined by
the Win32 API what will happen in such a case. It would be interesting to
try it and see what happens though :)
-cd