Messages in this thread | | | Date | Sat, 16 May 2015 00:30:41 +0100 | From | Russell King - ARM Linux <> | Subject | Re: [PATCH] ARM: tegra: cpuidle: implement cpuidle_state.enter_freeze() |
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On Fri, May 15, 2015 at 11:03:35AM +0200, Tomeu Vizoso wrote: > I have been looking and asking around, and seems like we should > actually leave FIQs enabled when the tick is frozen and only disable > them within enter_freeze. > > My understanding is that FIQ handlers are extremely limited in what > they can do, with the main use being NMI-like functionality. There are > a handful of other FIQ handlers in mainline, but they don't call into > any other kernel code and limit themselves to doing some basic I/O. > > The only reason why they should be disabled in enter_freeze is that > the context of the CPU that is going to a lower power state could > become corrupted if a FIQ gets fired during a save or restore > operation.
Right, that makes total sense.
(And yes, FIQ handlers are very limited in what they're allowed to do, since they can't take any locks without the potential for deadlock.)
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