It helps to attach the test code :)

P.

Prarit Bhargava wrote:

> Colleagues,
>
> I've identified the following critical issue where the hotplug 
> subsystem can cause OOM-killer to run.  IMO this is a critical issue 
> within hotplug -- in the case below, only the virtual console 
> subsystem is responsible.
>
> The virtual consoles that are being spawned are responsible for 2 
> hotplug events for every console opened -- one on the opening of the 
> console, and one on the closing of the console.
>
> If you run the tty2_test which opens and closes ttys (attached to this 
> email) you'll see THOUSANDS of hotplug events.  After running for 1 
> minute on a 16p ia64 I had well over 4000 hotplug events.
>
> If we're unlucky enough to fall below the low-water memory point at 
> the same time tty2_test is spawning, the OOM-killer starts up.  Memory 
> is taken up by the hotplug events ... and we're off into the weeds.
>
> The issue with the virtual console code is that it uses the 
> class_simple library.  This is a problem as the library pre-defines a 
> global kset parent as class_obj (or at least AFAICT).  This parent is 
> used by ALL subsystems using the class_simple, not just the virtual 
> console subsystem.
>
> This parent has a pointer to allow hotplug slot operations for all 
> it's children (including the virtual consoles).  IMO zero-ing this 
> pointer out is not a valid option as this would break hotplug op's for 
> many other subystems.
>
> ** I did notice that the class struct has it's own hotplug value -- 
> can/should this be used to override the parent's hotplug operations? **
>
> P.
>
>
>