From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Andrew Morton" Date: Tue, 06 Feb 2001 23:07:43 +0000 Subject: Re: Adding PCMCIA support to the kernel tree -- developers needed. Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-hotplug@vger.kernel.org David Brownell wrote: > > My short version of "why did that change" was that the addition of > network hotplugging turned up some races (the network driver API > wasn't designed for hotplugging, unlike USB or PCI, and some locks > were held so usermode "ifconfig" could deadlock) and changing all > that was the expedient way out. Andrew Morton can elaborate; > from test5 through test11, hotplugging was synchronous, without > any reported problems when used with USB. It was a deadlock, not a race. We were calling `/sbin/hotplug net' from within register_netdevice, with rtnl_lock held. /sbin/hotplug then called `ifconfig up', which wanted to claim rtnl_lock. My third (and as yet unapplied) call_usermodehelper patch rearranges the calls to '/sbin/hotplug net' so they happen outside the rtnl_lock, so I think we could use synchronous-exec mode there. (We don't have synchronous exec mode at present - that was the other part of the patch). Look. If we really think we need call_usermodehelper to be synchronous then let's make a swift and solid decision, present a good case to the boss. _______________________________________________ Linux-hotplug-devel mailing list http://linux-hotplug.sourceforge.net Linux-hotplug-devel@lists.sourceforge.net http://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel