[Vm-dev] Re: Cog on Linux

[Derek O'Connell]

On 22/07/10 22:20, Eliot Miranda wrote:
>
>
>
>
> Hi Paul,
>
> On Thu, Jul 22, 2010 at 2:14 PM, Paul DeBruicker<pdebruic at gmail.com>  wrote:
>
>>
>> Hi Eliot,
>>
>>
>>
>> On 07/22/2010 05:02 PM, vm-dev-request at lists.squeakfoundation.org wrote:
>>
>>> handle SIGUSR2 nostop noprint noignore
>>>
>>>
>> If I include the above line in my .gdbinit then gdb complains:
>>
>> Cannot find user-level thread for LWP XXXXX
>>
>> where XXXXX is the process number for the VM.  Sometimes the VM window
>> stays open and freezes at that point and sometimes it closes. Gdb then
>> states that the "Target is running" when I type in the commands you listed.
>>   If I comment the "handle SIGUSR2 ..." line out then I get this from those
>> commands:
>>
>
> just looks like the OS/run-time is not letting the program set a handler for
> SIGUSR2 and/or not allowing it to be caught.  This is a deal breaker.  Why
> it's happening I don't know, but currently Cog's heartbeat on linux depends
> on being able to catch SIGUSR2.

From: http://pauillac.inria.fr/~xleroy/linuxthreads/faq.html

H.4: With LinuxThreads, I can no longer use the signals SIGUSR1 and 
SIGUSR2 in my programs! Why?

The short answer is: because the Linux kernel you're using does not 
support realtime signals.