Global mutex problem on Linux

["Wharry, Brian J." <br...@ngc.com>]

Hi,
 
We are having a problem with the global mutex on Linux (in this case, on
Ubuntu).  Using APR v1.2.9, we are unable to get a global mutex to
provide inter-process locking, where under Windows it works fine.  In
searching the APR mailing list archive I've found some others who have
had the same problem, but it seems like it has yet to be fixed:
 
http://www.mail-archive.com/dev@apr.apache.org/msg14979.html
http://marc.info/?l=apr-dev&m=113253835410578&w=2
 
 
We are running a test application and opening two separate instances of
it from the command line.  Both apps attempt to create and lock a global
mutex with the same name.  We do not get any errors or warnings for
doing this, but the result was not what we expect.  Instead of one
process being prevented from locking the mutex, the two processes act
like they are accessing completely different mutexes and they are both
allowed to simultaneously lock the mutex.
 
Does anyone know if this will be fixed?  Or are we doing something
wrong?
 
I should note that one of our developers has worked around this problem
by using an APR Shared Memory segment and thread mutexes.
 
Thanks!
Brian
 
brian.wharry@ngc.com

RE: Global mutex problem on Linux

[Daniel May <da...@spryware.com>]

That is the correct work around, use Shared Memory and a shared pthread
mutex.

 

Daniel

 

 

From: Wharry, Brian J. [mailto:brian.wharry@ngc.com] 
Sent: Tuesday, December 04, 2007 2:37 PM
To: dev@apr.apache.org
Subject: Global mutex problem on Linux

 

Hi,

 

We are having a problem with the global mutex on Linux (in this case, on
Ubuntu).  Using APR v1.2.9, we are unable to get a global mutex to
provide inter-process locking, where under Windows it works fine.  In
searching the APR mailing list archive I've found some others who have
had the same problem, but it seems like it has yet to be fixed:

 

http://www.mail-archive.com/dev@apr.apache.org/msg14979.html

http://marc.info/?l=apr-dev&m=113253835410578&w=2

 

 

We are running a test application and opening two separate instances of
it from the command line.  Both apps attempt to create and lock a global
mutex with the same name.  We do not get any errors or warnings for
doing this, but the result was not what we expect.  Instead of one
process being prevented from locking the mutex, the two processes act
like they are accessing completely different mutexes and they are both
allowed to simultaneously lock the mutex.

 

Does anyone know if this will be fixed?  Or are we doing something
wrong?

 

I should note that one of our developers has worked around this problem
by using an APR Shared Memory segment and thread mutexes.

 

Thanks!

Brian

 

brian.wharry@ngc.com