Hi all,

this is the first patch to implement hotplug resource limitation 
(relative to 2.6.7-rc2-mm2).

Some sort of limitation is needed as call_usermodehelper just execve()s 
a program without any checks if enough resources (memory, cpu) are 
available. So loading a module which creates a lot of hotplug events may 
stall or even crash the machine.

It implements a semaphore holding the max # of concurrent hotplug / kmod 
processes, which blocks if the number has been reached. Any further 
attempt to call a helper program with call_usermodehelper will either be 
blocked (if the call is synchronous) or queued (if the call is 
asynchronous) until the semaphore is freed upon exit() from a previous 
call. The total number is adjustable with a kernel commandline option
'khelper_max', but restricted to something sane, as setting this too low 
would result in a deadlock from request_module (as this might be called 
recursively from several modules).

This patch also eliminates the need for the 'track number of kmod 
processes' hach in request_module, as it implements the same 
functionality on a broader scale.

Please apply.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke			hare@suse.de
SuSE Linux AG				S390 & zSeries
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