2018-07-12 20:32 GMT+09:00 Dirk Gouders <dirk@xxxxxxxxxxx>: > Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> writes: > >> 2018-07-09 20:39 GMT+09:00 Dirk Gouders <dirk@xxxxxxxxxxx>: >>> Dirk Gouders <dirk@xxxxxxxxxxx> writes: >>> >>>> Dirk Gouders <dirk@xxxxxxxxxxx> writes: >>>> >>>>> Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> writes: >>>>> >>>>>> syncconfig updates the .config only when sym_change_count > 0, i.e. >>>>>> any change in config symbols has been detected. >>>>>> >>>>>> Not only symbols but also comments are contained in the .config file. >>>>>> If only comments are updated, they are not fed back to the .config, >>>>>> then the stale comments are left-over. Of course, this is just a >>>>>> matter of comments, but why not fix it. >>>>> >>>>> Hello Masahiro, >>>>> >>>>> I am currently looking at and testing this series. >>>>> >>>>> First: For this patch I would suggest to also edit the syncconfig >>>>> section of "conf --help". >>>>> >>>>> Further, on a slow laptop, I was suspecting, this patch to cause full >>>>> rebuilds of everything, each time I ran "make syncconfig" followed by >>>>> "make" but could not verify this on another machine, so perhaps I am >>>>> just (for testing purposes) removing the wrong files (modules.builtin >>>>> for example) -- I am still testing. >>>>> >>>>> But, what irritates me with testing is that (also without your >>>>> patches) two consecutive "make" produce different output, one of them >>>>> always shows a warning and this is reproducable. I just want to make >>>>> sure there is no other problem that influences my testing: >>>>> >>>>> $ make >>>>> CALL scripts/checksyscalls.sh >>>>> DESCEND objtool >>>>> CHK include/generated/compile.h >>>>> DATAREL arch/x86/boot/compressed/vmlinux >>>>> Kernel: arch/x86/boot/bzImage is ready (#15) >>>>> Building modules, stage 2. >>>>> MODPOST 211 modules >>>>> >>>>> $ make >>>>> CALL scripts/checksyscalls.sh >>>>> DESCEND objtool >>>>> CHK include/generated/compile.h >>>>> LD arch/x86/boot/compressed/vmlinux >>>>> ld: arch/x86/boot/compressed/head_64.o: warning: relocation in read-only section `.head.text' >>>>> ld: warning: creating a DT_TEXTREL in object. >>>>> ZOFFSET arch/x86/boot/zoffset.h >>>>> AS arch/x86/boot/header.o >>>>> LD arch/x86/boot/setup.elf >>>>> OBJCOPY arch/x86/boot/setup.bin >>>>> OBJCOPY arch/x86/boot/vmlinux.bin >>>>> BUILD arch/x86/boot/bzImage >>>>> Setup is 15580 bytes (padded to 15872 bytes). >>>>> System is 8069 kB >>>>> CRC e01d75ec >>>>> Kernel: arch/x86/boot/bzImage is ready (#15) >>>>> Building modules, stage 2. >>>>> MODPOST 211 modules >>>> >>>> I spent some more time with the behaviour described above and bisected >>>> to the commit after that two consecutive invocations of "make" (on an >>>> already compiled tree) seem to do different things. That commit is >>>> 98f78525371b55cc (x86/boot: Refuse to build with data relocations), so I >>>> put Kees and Ingo on CC. >>>> >>>> I did the bisecting on another system, so I'll provide the output of two >>>> consecutive "make" on an already compiled tree on that machine: >>>> >>>> $ make >>>> CALL scripts/checksyscalls.sh >>>> DESCEND objtool >>>> CHK include/generated/compile.h >>>> DATAREL arch/x86/boot/compressed/vmlinux >>>> Kernel: arch/x86/boot/bzImage is ready (#48) >>>> Building modules, stage 2. >>>> MODPOST 165 modules >>>> >>>> $ make >>>> CALL scripts/checksyscalls.sh >>>> DESCEND objtool >>>> CHK include/generated/compile.h >>>> LD arch/x86/boot/compressed/vmlinux >>>> ZOFFSET arch/x86/boot/zoffset.h >>>> AS arch/x86/boot/header.o >>>> LD arch/x86/boot/setup.elf >>>> OBJCOPY arch/x86/boot/setup.bin >>>> OBJCOPY arch/x86/boot/vmlinux.bin >>>> BUILD arch/x86/boot/bzImage >>>> Setup is 15644 bytes (padded to 15872 bytes). >>>> System is 6663 kB >>>> CRC 3eb90f40 >>>> Kernel: arch/x86/boot/bzImage is ready (#48) >>>> Building modules, stage 2. >>>> MODPOST 165 modules >>>> >>>> If I comment out $(call if_changed,check_data_rel) in >>>> arch/x86/boot/compressed/Makefile, two consecutive "make" produce >>>> identical output i.e. seem to not do different things: >>>> >>>> $ make >>>> CALL scripts/checksyscalls.sh >>>> DESCEND objtool >>>> CHK include/generated/compile.h >>>> Kernel: arch/x86/boot/bzImage is ready (#49) >>>> Building modules, stage 2. >>>> MODPOST 165 modules >>>> >>>> $ make >>>> CALL scripts/checksyscalls.sh >>>> DESCEND objtool >>>> CHK include/generated/compile.h >>>> Kernel: arch/x86/boot/bzImage is ready (#49) >>>> Building modules, stage 2. >>>> MODPOST 165 modules >>>> >>>> So, I guess this different behaviour of two consecutive "make" is not >>>> intentional but I am failing to understand why it happens. >>> >>> I think, I solved the puzzle and perhaps, that saves others some time: >>> >>> The problem is that "if_changed" was not designed for multiple use >>> inside a recipe and in the case of compressed/vmlinux, the 2-fold use >>> created a kind of flip-flop for situations when nothing has to be done >>> to build the target. >>> >>> Because each of the two users of "if_changed" stores it's footprint in >>> .vmlinux.cmd but that file then isn't re-read, one of the two >>> "if_changed" calculates that nothing has to be done wheras the other one >>> recognizes a change in the commandline, because it sees the command-line >>> for the other part of the reciepe. >>> >>> In the next make, the roles flip, because the previously satisfied >>> "if_changed" now sees the command-line of the other one. And so on... >>> >>> I am not a Kbuild expert but the attached patch fixes that problem by >>> introducing "if_changed_multi" that accepts two commands -- one whose >>> commandline should be checked and a second one that should be >>> executed. >> >> >> if_changed should not appear multiple times in one target. >> >> I think the simplest fix-up is to >> create a new command that combines >> 'cmd_check_data_rel' and 'cmd_ld'. >> >> >> quiet_cmd_link-vmlinux = LD $@ >> cmd_link-vmlinux = $(cmd_check_data_rel); $(cmd_ld) >> >> $(obj)/vmlinux: $(vmlinux-objs-y) FORCE >> $(call if_changed,link-vmlinux) >> >> Kbuild also supports if_changed_rule, >> but the usage is more complex. >> >> There are only a few usages: >> https://github.com/torvalds/linux/blob/v4.17/scripts/Makefile.build#L288 > > Just for completeness I will copy in part of a reply from Kees that > shows how double-colon rules can also avoid multiple use of if_changed > for one target: > > -$(obj)/vmlinux: $(vmlinux-objs-y) FORCE > - $(call if_changed,check_data_rel) > +$(obj)/vmlinux:: $(vmlinux-objs-y) > + $(call cmd,check_data_rel) > +$(obj)/vmlinux:: $(vmlinux-objs-y) FORCE > $(call if_changed,ld) It is difficult to use double-colon rules in a _sane_ way. The first one just checks data_rel, but does not actually generate anything. Such targets should be marked as .PHONY, but $(obj)/vmlinux is not a phony target. This is strange. > The combined command seems to have the advantage that every command to > build the target gets recorded in the .cmd file > > A search showed me that we have two more users that use if_changed more > than once for a single target: > > arch/microblaze/boot/Makefile (fourfold) > arch/sparc/boot/Makefile (2 times twofold) > > The sparc case seems to apply to any of the two suggested fixes, Neither is correct. $(obj)/uImage: $(obj)/image.gz $(call if_changed,uimage) $(call if_changed,uimage.o) should be split into two targets. $(obj)/uImage: $(obj)/image.gz FORCE $(call if_changed,uimage) $(obj)/uImage.o: $(obj)/uImage FORCE $(call if_changed,uimage.o) It is wrong in multiple ways. FORCE is missing too. but > microblaze uses if_changed in a pattern rule and also makes use of > parameter arguments in the sub-commands: > > $(obj)/simpleImage.%: vmlinux FORCE > $(call if_changed,cp,.unstrip) > $(call if_changed,objcopy) > $(call if_changed,uimage) > $(call if_changed,strip,.strip) > @echo 'Kernel: $(UIMAGE_OUT) is ready' ' (#'`cat .version`')' Probably, this is the same. Create a target for each step. > In this case, double colons would have a different meaning and the > combined command solution would result in a change of the sub-commands, > as well. I note this in case Michal perhaps has other preferences. > > > In addition to extend the documentation, we could modify if_changed to > warn about it is being used more than once for a target: > > # Execute command if command has changed or prerequisite(s) are updated. > if_changed = $(if $(filter-out undefined,$(origin if_changed_$@)), \ > @set -e; \ > echo "Warning: $@: multiple use of if_changed!" >&2; , \ > @set -e $(eval if_changed_$@ := 1) ; ) \ > $(if $(strip $(any-prereq) $(arg-check)), \ > $(echo-cmd) $(cmd_$(1)); \ > printf '%s\n' 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd, :) > > But this fires only if if_changed is actually called and it defines many > variables for just that purpose, so this is perhaps not what we want... > I do not want to mess up Makefile. Please do this check in scripts/checkpatch.pl if you want. -- Best Regards Masahiro Yamada -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
