Experimental Physics and
Industrial Control System

Dirk Zimoch <[email protected]> · Tue, 23 Jun 2009 09:59:34 +0200

Hi Bruno,

From what I can see in the macro definition of gdd_NEWDEL_NEW(gdd) in

gddNewDel.h, the gddScalar::new() operator is not fully thread safe.

Initialization of the freelist is not protected. Thus, calling gdd*::new() for

the first time in two different threads may crash. Maybe using gdd*::new() the

first time while still in single threaded context may cure the problem.

Dirk

Bruno Coudoin wrote:

Hi,

Tonight I found something odd. I am perhaps doing something wrong but
after several test the results were consistant.

I have a multithreaded application, at startup each thread creates
several gdd. It ends up frequently in the following SIGSEGV:
  Program received signal SIGSEGV, Segmentation fault.
  [Switching to Thread 0x98a35b90 (LWP 1020)]
  0x00f2b2b8 in gdd::operator new (size=44) at ../gdd.cc:26
  26      gdd_NEWDEL_NEW(gdd)

My code to create the gdd is as simple as:
  gdd *pDD;
  pDD = new gddScalar ( gddAppType_value, aitEnumInt32 );

It seems like my program crashes at startup but if it passed the first
gdd creation of each threads, it becomes stable after that. More threads
I have, more chance I have to see the crash.

My configuration:
Epics 3.14.10
CentOS 5.3
Multi core processor.

Has anybody ever seen this issue? I'll try to dig further tomorrow, if
someone has ideas on workarounds or tests to do to refine the issue,
your welcome.

Bruno.

--
Dr. Dirk Zimoch
Paul Scherrer Institut, WBGB/006
5232 Villigen PSI, Switzerland
Phone +41 56 310 5182

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System