Re: [PATCH] Limit number of concurrent hotplug processes

[Andrew Morton]

Hannes Reinecke <hare@xxxxxxx> wrote:
>
> the attached patch limits the number of concurrent hotplug processes.
>  Main idea behind it is that currently each call to call_usermodehelper 
>  will result in an execve() of "/sbin/hotplug", without any check whether 
>  enough resources are available for successful execution. This leads to 
>  hotplug being stuck and in worst cases to machines being unable to boot.
> 
>  This check cannot be implemented in userspace as the resources are 
>  already taken by the time any resource check can be done; for the same 
>  reason any 'slim' programs as /sbin/hotplug will only delay the problem.

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?

>  Any comments/suggestions welcome; otherwise please apply.

I suggest you just use a semaphore, initialised to a suitable value:


static struct semaphore foo = __SEMAPHORE_INITIALIZER(foo, 50);


{
	...
	down(&foo);
	...
	up(&foo);
	...
}

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