On Tue, Jun 05, 2018 at 09:17:52AM +0200, Miroslav Benes wrote: > On Mon, 4 Jun 2018, Josh Poimboeuf wrote: > > > On Mon, Jun 04, 2018 at 04:16:35PM +0200, Miroslav Benes wrote: > > > An administrator may send a fake signal to all remaining blocking tasks > > > of a running transition by writing to > > > /sys/kernel/livepatch/<patch>/signal attribute. Let's do it > > > automatically after 10 seconds. The timeout is chosen deliberately. It > > > gives the tasks enough time to transition themselves. > > > > > > Theoretically, sending it once should be more than enough. Better be safe > > > than sorry, so send it periodically. > > > > This is the part I don't understand. Why do it periodically? > > I met (rare!) cases when doing it once was not enough due to a race and > the signal was missed. However involved testcases were really artificial. > > > Instead, might it make sense to just send the signals once, and if that > > doesn't work, reverse the transition? Then we could make patching a > > synchronous operation. But then, it might be remotely possible that the > > reverse operation also stalls (e.g., on a kthread). So, maybe it's best > > to just leave all these controls in the hands of the user. > > And there is 'force' option... > > So given all this, I'd call klp_send_signals() once and then leave it up > to the user. Would that work for you?
Well, I don't know. Since the patching process will already need to be managed by user space, what's the benefit of having the kernel doing only this part of it? -- Josh
