Re: [PATCH v6 2/3] CPU hotplug, stop-machine: Plug race-window that leads to "IPI-to-offline-CPU"

[Peter Zijlstra]

On Fri, May 23, 2014 at 08:15:35PM +0530, Srivatsa S. Bhat wrote:
> >> +		 * During CPU offline, we don't want the other CPUs to send
> >> +		 * IPIs to the active_cpu (the outgoing CPU) *after* it has
> >> +		 * disabled interrupts (because, then it will notice the IPIs
> >> +		 * only after it has gone offline). We can prevent this by
> >> +		 * making the other CPUs disable their interrupts first - that
> >> +		 * way, they will run the stop-machine code with interrupts
> >> +		 * disabled, and hence won't send IPIs after that point.

That's complete nonsense, you can send IPIs all you want with interrupts
disabled.

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