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From: "David S. Miller" <davem@redhat.com>
Subject: Re: [PATCH] post-sysfs netdev cleanup
Date: Sun, 25 May 2003 19:24:17 -0700 (PDT)
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   From: Stephen Hemminger <shemminger@osdl.org>
   Date: Fri, 23 May 2003 16:47:35 -0700

   Seems like a good idea too.
   
Ok, great.

Stephen, I think we need to find a way to put the device
registration call outside of the RTNL semaphore.  I removed
in the unregister case, but to be complete we have to push it out in
the register path too.

The reason for all of these issues is that link_watch grabs the RTNL
semaphore, and this runs via keventd.  Thus, trying to invoke any
usermode helper (/sbin/hotplug etc.) while holding the RTNL semaphore
can deadlock.