Messages in this thread | | | Subject | Re: CPU hotplug: system hang on CPU hot remove during `pfmon --system-wide' | From | Rusty Russell <> | Date | Wed, 30 May 2007 12:42:01 +1000 |
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On Tue, 2007-05-29 at 13:56 -0700, Linus Torvalds wrote: > > On Mon, 28 May 2007, Srivatsa Vaddagiri wrote: > > > > So is it settled now on what approach we are going to follow (freezer > > vs lock based) for cpu hotplug? I thought that Linus was not favouring freezer > > based approach sometime back .. > > As far as I'm concerned, we should > - use "preempt_disable()" to protect against CPU's coming and going > - use "stop_machine()" or similar that already honors preemption, and > which I trust a whole lot more than freezer. > - .. especially since this is already how we are supposed to be protected > against CPU's going away, and we've already started doing that (for an > example of this, see things like e18f3ffb9c from Andrew)
Indeed, this is how it was supposed to work.
Note that it is possible to make stop_machine() an even larger hammer, by scheduler mods to flush all the preempted tasks. This would drop the requirement for preempt_disable().
But cute as that would be, I've been waiting until someone demonstrates an actual need...
Rusty.
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