Re: [PATCH] Limit number of concurrent hotplug processes

[Christian Borntraeger <linux-kernel@borntraeger.net>]

Andrew Morton wrote:
> Hannes Reinecke <hare@suse.de> wrote:
> > the attached patch limits the number of concurrent hotplug processes.

> hm, it's a bit sad that this happens.  Are you able to tell us more about
> what is causing such an explosion of module probes?

I dont know exactly which scenario Hannes has seen, but its quite simple to 
trigger this scenario with almost any s390/zSeries.

Using the Hardware Management Console or z/VM you are able to hotplug 
(deactive/activate/attach/detach) almost every channel path. As a channel 
path can connect a big bunch of devices lots of machine checks are 
triggered, which causes lots of hotplugs. The same amount of machine checks 
could happen if a hardware failure happens. 

Some month ago I played around with a diet version of  hotplug. This program 
was fast and small enough to make my scenario work properly. Nevertheless, 
as hannes already stated this will only delay the problem. 

cheers

Christian