Re: synchronization

From:

"Doug Harrison [MVP]" <dsh@mvps.org>

Newsgroups:

microsoft.public.vc.language

Date:

Sat, 11 Jul 2009 15:49:17 -0500

Message-ID:

<1buh55lrvkobr5pe1nnrkse5krtih9j888@4ax.com>

On Sat, 11 Jul 2009 15:42:19 +0530, "jjoohhnn"
<jjoohhnn@microsoft.discussions.com> wrote:

Hi All,

I have ProcessA and ProcessB. Codes are different in these two
processes. Now, these two are trying to update database. So, I tried
synchronize the database operations by using CMutex. But, it's failing at
CSingleLock(&mutex, TRUE) that time database was not locked by any other
app.

Is is correct approach?

If you have actually written:

   CSingleLock(&mutex, TRUE);

Then that creates a temporary object that is immediately destroyed and is
incorrect. You need to use an actual variable:

   CSingleLock lk(&mutex, TRUE);

The lock will be released when lk is destroyed. Another way to mess this up
is to write:

   CSingleLock lk(&mutex);

MS actually defaults the "acquire lock" argument to FALSE. If none of this
seems to apply, the only other thing I can think of is to verify the mutex
is being created/opened correctly in both processes.

Is there any better solution than this?

See what Alex said.

--
Doug Harrison
Visual C++ MVP