| Re: Limiting the number of VM instances [message #37733 is a reply to message #37645] |
Thu, 22 January 2004 08:02  |
robert.dimeo
Messages: 42
Registered: November 2001
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Member |
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robert.dimeo@nist.gov (Rob Dimeo) wrote in message news:<cb539436.0401131159.7bff3179@posting.google.com>...
> Hi,
>
> Is it possible to limit the number of VM instances running at once?
> Let's say that I have APP.SAV running from the VM. I can launch
> another VM session with another version of APP.SAV running. Can I
> restrict this so that only one application runs?
>
> This is probably an OS issue so using XREGISTERED won't work. I would
> like to do this in WIN2K.
>
> Thanks,
>
> Rob
Hi again. Once again the helpful folks at RSI suggested a solution
and I wrote a function encapsulating the logic called
LIMIT_VM_INSTANCE. The main idea is to use a shared memory segment.
In addition to a listing of the function I also include here a simple
widget program that uses this function. Note of course that you must
go through the usual step of creating a SAVE file to use it in the VM.
Hope that this is useful.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;
function limit_vm_instance, INIT = init, $
EXIT = exit, $
PROCESS_NAME
; Keywords:
;
; INIT: set prior to defining the widgets
; EXIT: set in the cleanup
;
; Parameters:
;
; PROCESS_NAME: required string variable (that might be set
; to the same string as the name with which the
; widget is registered with XMANAGER for instance).
;
if n_params() eq 0 then begin
!error_state.msg = 'You must pass in a PROCESS_NAME variable'
return,0
endif
if keyword_set(init) then begin
if lmgr(/vm) then begin
os_handle = 'mysegment'+'_'+process_name
shmmap, process_name, template = [0B], $
os_handle = os_handle
v = shmvar(process_name)
if (v[0] eq 1) then begin
msg = 'An instance of this code is already running.'
v = dialog_message(msg, /error)
shmunmap,process_name
return,0
endif
v[0] = 1
endif
return,1
endif
if keyword_set(exit) then begin
if lmgr(/vm) then shmunmap,process_name
return,1
endif
return,1
end
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;
; Simple widget application that uses this follows
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;
pro shared_example_cleanup,tlb
widget_control,tlb,get_uvalue = pstate
; Call the function that limits the number of VM instances
; with the EXIT keyword set. Note that we must pass in
; the "register_name" for the application which is stored
; in the state structure.
ret = limit_vm_instance(/exit,(*pstate).register_name)
ptr_free,pstate
end
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;
pro shared_example_event,event
uname = widget_info(event.id,/uname)
case strupcase(uname) of
'QUIT': widget_control,event.top,/destroy
else:
endcase
end
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;
pro shared_example
; Call the function that limits the number of VM instances
; with the INIT keyword set. Note that we also will need to
; call this same function with the EXIT keyword set in a
; cleanup routine...this is necessary to unmap the variable that
; is in shared memory. We need a unique process name for
; the memory segment so we can just use the name with which
; we'll register the application with the XMANAGER.
register_name = 'shared_example'
ret = limit_vm_instance(/init,register_name)
if not ret then return
; Limit the instance in an IDL session using the usual
; XREGISTERED function.
if xregistered(register_name) then begin
msg = 'An instance of this code is already running.'
v = dialog_message(msg, /error)
return
endif
; The following simple widget code just puts up a QUIT button.
tlb = widget_base(title = 'shared memory example', $
/tlb_frame_attr,/col)
void = widget_button(tlb,value = 'quit',xsize = 200, $
uname = 'quit')
widget_control,tlb,/realize
; Store the "register_name" variable in a state structure and
; set the uvalue of the TLB to a pointer to the state structure.
state = {register_name:register_name}
pstate = ptr_new(state)
widget_control,tlb,set_uvalue = pstate
; We must use a cleanup routine in order to unmap the variable
; from shared memory so specify it here. Remember to use the
; register_name variable here.
xmanager,register_name,tlb,/no_block, $
cleanup = 'shared_example_cleanup', $
event_handler = 'shared_example_event'
end
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