On Wed, Dec 18, 2019 at 01:11:14PM +0000, Mark Brown wrote: > On Wed, Dec 18, 2019 at 01:21:57PM +0100, Greg KH wrote: > > On Wed, Dec 18, 2019 at 11:34:58AM +0000, Mark Brown wrote: > > > On Tue, Dec 17, 2019 at 11:51:55PM +0800, Siddharth Kapoor wrote: > > > > > I would like to share a concern with the regulator patch which is part of > > > > 4.9.196 LTS kernel. > > > > That's an *extremely* old kernel. > > > It is, but it's the latest stable kernel (well close to), and your patch > > was tagged by you to be backported to here, so if there's a problem with > > a stable branch, I want to know about it as I don't want to see > > regressions happen in it. > > I don't track what's in older stable kernels, it wanted to go back at > least one kernel revision but the issue has been around since forever. Ok, you can always mark patches that way if you want to :) > > > I've got nothing to do with the stable kernels so there's nothing I can > > > do here, sorry. > > > Should I revert it everywhere? This patch reads as it should be fixing > > problems, not causing them :) > > The main targets were whatever Debian and Ubuntu are shipping (and to a > lesser extent SuSE or RHEL but they don't use stable directly), it's > less relevant to anything that only gets used on embedded stuff. It's > right on the knife edge of what I'd backport but since that's way less > enthusiastic than stable is in general these days. I've reverted it now from 4.14.y and 4.9.y. > > > Possibly your GPU supplies need to be flagged as always on, possibly > > > your GPU driver is forgetting to enable some supplies it needs, or > > > possibly there's a missing always-on constraint on one of the regulators > > > depending on how the driver expects this to work (if it's a proprietary > > > driver it shouldn't be using the regulator API itself). I'm quite > > > surprised you've not seen any issue before given that the supplies would > > > still be being disabled earlier. > > > Timing "luck" is probably something we shouldn't be messing with in > > stable kernels. How about I revert this for the 4.14 and older releases > > and let new devices deal with the timing issues when they are brought up > > on new hardware? > > To be clear this is more a straight up bug in their stuff than the sort > of thing you'd normally think of as a race condition, we're talking > about moving the timing by 30 seconds here. The case that we saw > already was just a clear and obvious bug that was made more visible (the > driver was using the wrong name for a supply so lookups were always > failing but some sequence of events meant it didn't produce big runtime > failures). > > If you don't want to be messing with timing luck then you probably want > to be having a look at what Sasha's bot is doing, it's picking up a lot > of things that are *well* into this sort of territory (and the bad > interactions with out of tree code territory). I personally would not > be using stable these days if I wasn't prepared to be digging into > something like this. I watch what his bot is doing, and we have tons of testing happening as well, which is reflected by the fact that THIS WAS CAUGHT HERE. This is a sign that things are working, it's just that some SoC trees are slower than mainline by a few months, and that's fine. It's worlds better than the SoC trees that are no where close to mainline, and as such, totally insecure :) thanks, greg k-h
