From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Hansen Date: Tue, 29 Jun 2004 22:41:36 +0000 Subject: Re: How to notify app of changed cpu/mem/io node configuration? Message-Id: <1088548896.23932.72.camel@nighthawk> List-Id: References: <20040628173808.04718b83.pj@sgi.com> In-Reply-To: <20040628173808.04718b83.pj@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-hotplug@vger.kernel.org On Mon, 2004-06-28 at 23:24, Greg KH wrote: > On Mon, Jun 28, 2004 at 05:38:08PM -0700, Paul Jackson wrote: > > I can imagine using for notification a new signal, that could be sent by > > an administrator or system service (batch manager, perhaps) to tasks if > > their allowed CPUs or Memory Nodes or other such had changed. > > I recall some initial proposals for when CPUs were offlined, to send the > applications that were bound to those CPUs a specific signal, but I do > not know if that got implemented or not. Anyone know? I don't see anything in the various signal.h files that looks likely. But, we'll probably need some kind of synchronous process notification at some point. If an app gets itself in a bad state such that it has no possibility of being scheduled, or gets itself into some other hopeless state due to a hotplug action, the kernel will likely have the option to kill it. I think the problem for the kernel comes when we consider how to notify the app. Doing a hotplug event and having the scripts send an appropriate signal isn't really a viable option because the kernel wouldn't really know when each app had a chance to handle the signal. Sleeping for 5 seconds and hoping for the best probably isn't the best option, either. :) The other option would be to have the kernel send signals to the processes, and recheck the "impossible state" after the signal has been handled. I don't really remember how the discussions about CPU hotplug ended, but I wonder if a much more generic signal could be of more use than a single task CPU hotplug signal. What about a SIGHOTPLUG that can be used whenever the kernel notices that a task is using a resource that's being hotplugged? -- Dave ------------------------------------------------------- This SF.Net email sponsored by Black Hat Briefings & Training. Attend Black Hat Briefings & Training, Las Vegas July 24-29 - digital self defense, top technical experts, no vendor pitches, unmatched networking opportunities. Visit www.blackhat.com _______________________________________________ Linux-hotplug-devel mailing list http://linux-hotplug.sourceforge.net Linux-hotplug-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel