[Vm-dev] Re: RFC: Unix 3.11.3-2116 VM

[Andreas Raab]

Ian Piumarta wrote:
> Is enabling IMAGE_DUMP in sqUnixMain.c sufficient for what you need?  We 
> could also have an option that names an image dump file, disabling the 
> dump if no name is given but still printing the stack.

Saving the image can be useful but only when it's decoupled from dumping 
the call stack. Dumping the stack is a non-destructive action so it can 
be done to investigate the status of the image. I have seen situations 
where images were at 100% but where I found that the activity actually 
didn't cause any harm, so no emergency action was necessary. Think of 
the stack dump as purely informative: You want to find out what's going 
on without actually shooting the image. Whatever does that works for me.

> BTW: it is extremely dangerous to print the stack asynchronously from 
> within an interrupt handler.  In the Unix VM, SIGHUP sets a flag that is 
> checked and prints the stack from ioProcessEvents (which is safe) and 
> SIGQUIT prints it asynchronously from the handler.

Interesting. We've never had any issues with that.

Cheers,
   - Andreas