On Mon, Dec 17, 2018 at 6:45 AM Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx> wrote: > > [Re: [Regression 4.15] Can't kill CONFIG_UNWINDER_ORC with fire or plague.] On 29/12/2017 (Fri 13:18) Paul Gortmaker wrote: > > > [Re: [Regression 4.15] Can't kill CONFIG_UNWINDER_ORC with fire or plague.] On 29/12/2017 (Fri 10:47) Josh Poimboeuf wrote: > > > > > This seems to be related to a kconfig quirk where only silentoldconfig > > > updates the include/config/auto.conf file. The other config targets > > > (oldconfig, defconfig, etc) don't touch it. It seems intentional, but I > > > have no idea why. > > > > > > That causes the Makefile to get stale data for 'CONFIG_*' variables when > > > it includes auto.conf. So I don't think this is specific to the ORC > > > check. It seems like it could also cause bugs elsewhere. > > > > OK, good - you agree with my initial diagnosis of stale auto.conf then. > > Not sure what Randy was testing when he said he couldn't reproduce it. > > > > > The below (ugly) patch fixes it, though I'm not sure this is the best > > > way to do it. We probably need Masahiro or Michal to chime in here. > > > > Yep, that is why I intentionally put the kbuild folks on the To/Cc of > > the original report (and ran away screaming at the prospect of debugging > > Makefiles on xmas day). But with holidays and all, it might not be > > until early January before they have a chance to reply. > > It is nearly a year later and we still have this false positive. > > paul@sm:~/git/linux-head$ make -j12 > /dev/null > Makefile:966: *** "Cannot generate ORC metadata for CONFIG_UNWINDER_ORC=y, > please install libelf-dev, libelf-devel or elfutils-libelf-devel". Stop. > paul@sm:~/git/linux-head$ grep UNWINDER_ORC .config > # CONFIG_UNWINDER_ORC is not set > > We do know a bit more now -- the auto.conf issue has been independently > confirmed and "fixed" for other subsystems/issues since, like RETPOLINE: > > --------------------- > commit 25896d073d8a0403b07e6dec56f58e6c33678207 > Author: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> > Date: Wed Dec 5 15:27:19 2018 +0900 > > x86/build: Fix compiler support check for CONFIG_RETPOLINE > > It is troublesome to add a diagnostic like this to the Makefile > parse stage because the top-level Makefile could be parsed with > a stale include/config/auto.conf. > > Once you are hit by the error about non-retpoline compiler, the > compilation still breaks even after disabling CONFIG_RETPOLINE. > --------------------- > > I'm not sure if we want to treat this on a per config option each time > again and again, or undertake a more global kbuild approach, but it does > warrant a mention and a re-examination before we "solve" this again. I did not notice this thread (perhaps, it fell into my crack during the holidays) but I actually tried to fix this twice in a sophisticated way in the past. The first attempt (https://patchwork.kernel.org/patch/10516049/) was rejected by Josh Poimboeuf. The second one (https://patchwork.kernel.org/patch/10643245/) turned out not working as expected. Now, I am preparing for the third attempt, but it will take time for review. What I can do now is the similar fix-up as commit 25896d073d8. I will post a cheesy fix-up patch. -- Best Regards Masahiro Yamada
