When is the handle with name \GLOBAL?? is created?

Question

Hi,

I have a dump of process where the handle count in the process did reached 16 million handles (which is the maximum allowed handles per process). Hence the process got hanged.

From dump (This is second dump where the handle count is high but not max limit.) I get following data :

53778 Handles 
Type            Count    
None            2    
Event           238    
Section         3    
File            84    
Port            16    
**Directory       53120**    
Mutant          35    
WindowStation   2    
Semaphore       151    
Key             42    
Token           4    
Process         1    

0:000> !handle 9735 f    
Handle 00009735    
  Type          Directory    
  Attributes    0x10    
  GrantedAccess 0x1:    
  HandleCount   53575    
  PointerCount  53788    
  Name          \GLOBAL??
  No object specific information available

There are many such handles open with Name : \GLOBAL?? and type Directory. Here I want to know in what scenarios do we see this particular handle being created? Is there any way to know the code where the leak is occurring from the full dump?

-Akshay.

Answer 1

I believe you are using WinDBG.

If I am not wrong, "\GLOBAL??" indicates that your symbolic link is relates to all sessions. On Win2K it was "\??". Symbolic links and Handles can be local to a session. For an example: I can create a Mutex handle and make it local to each terminal service sessions. This can be done by prefixing the mutex name explicitly with a "Global\" or "Local\" to create the object in the global or local session name space. http://msdn.microsoft.com/en-us/library/ms682411(VS.85).aspx

Answer 2

Is this reproducible? If so, you should try the !htrace extension.

Answer 3

In Windows NT, the old DOS filesystem is essentially a set of shortcuts. This is necessary because it's a multi-user filesystem. Your H:\ drive might differ from someone elses H:\ drive. Hence, both are implemented as shortcuts or symbolic links.

SysInternals Process Monitor has a handle viewm and IIRC can capture a stack dump for each file operation. That of course adds up quickly; you'll need to learn its filters.